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Gottlieb System 1 Pinball
Repair from 1977 to 1980

All text and pictures copyright by cfh@provide.net (Clay Harrell) unless otherwise noted.
Document date: 07/01/14.
Copyright 1998-2014, all rights reserved.

Scope: Includes Gottlieb first generation of solid state System 1 pinball games from Cleopatra (11/77) to Asteroid Annie (12/80).

Internet Availability of this Document.
Updates of this document are available at http://pinrepair.com if you have Internet access.

IMPORTANT: Before Starting!
IF YOU HAVE NO EXPERIENCE IN CIRCUIT BOARD REPAIR, YOU SHOULD NOT TRY TO FIX YOUR OWN PINBALL GAME! Before you start any pinball circuit board repair, review the document at http://pinrepair.com/begin, which goes over the basics of circuit board repair. Since these pinball repair documents have been available, repair facilities are reporting a dramatic increase in the number of ruined ("hacked") circuit boards sent in for repair. Most repair facilities will NOT repair your circuit board after it has been unsuccessfully repaired ("hacked") by you. If you aren't up to repairing your circuit boards yourself, I highly recommend checking out the parts and repair web page at pinrepair.com/parts.htm.

Table of Contents

Bibliography and Thanks.
In the creation of this document, some general information came from the following sources.

  • 1978 Gottlieb Service Manual, 2nd Edition.
  • Tuukka Kalliokoski web articles on system1 overview.
  • John Robertson web articles on grounding.
  • Tim Arnold for his miscellaneous tips.
  • Leon's web articles.
  • PaPinball.com web based articles on system1 machines.
Thanks to Eric A. for loaning me a Pascal CPU board and Jim Palson giving me a system1 wiring harness and transformers to make a test fixture. Thanks to all the people that helped with this document.


1a. Getting Started: Tools and Schematics
1b. Getting Started: System1 Games List, Numbers

Gottlieb System1 Games
Game Date Type of Sound CPU ROM Sound ROM Production Notes
Cleopatra 11-1977 Chimes A or 409 ROM none 7300 1600 + 950 EMs made
Sinbad 05-1978 Chimes B ROM none 12000 950 + 730 EMs made
Joker Poker 06-1978 Chimes C ROM none 9280 825 EMs made
Close Encounters 10-1978 Electronic Chime Board G ROM none 9950 470 EMs made
Dragon 10-1978 Electronic Chime Board D ROM none 6550 507 EMs made
Charlies Angles 11-1978 Electronic Chime Board H ROM none 7600 350 EMs made
Solar Ride 02-1979 Electronic Chime Board E ROM none 8800 365 EMs made
Count Down 05-1979 Electronic Chime Board F ROM none 9899 215 EMs made (Space Walk)
Pinball Pool 08-1979 Electronic Chime Board I ROM none 7200
Totem 10-1979 Multi Sound Board J ROM J-Snd ROM 6643
Incredible Hulk 10-1979 Multi Sound Board K ROM K-Snd ROM 6150
Genie 11-1979 Multi Sound Board L ROM L-Snd ROM 6800
Buck Rogers 01-1980 Multi Sound Board N ROM N-Snd ROM 7410
Torch 02-1980 Multi Sound Board P ROM P-Snd ROM 3880
Roller Disco 02-1980 Multi Sound Board R ROM R-Snd ROM 2400
Astroid Annie
and the Aliens
12-1980 Multi Sound Board S ROM S-Snd ROM 211

Note there were some conversion kits made for System1 games too. These include:

  • Movie by Bell Games, 1982 (playfield copy of Zaccaria Pinball Champ)
  • Sky Warrior by IDI, 1983 (Fast Draw playfield copy)
  • Tiger Woman by IDI, 1982 (playfield copy of Jungle Queen)
  • Sahara Love by Christian Automatic (conversion of Sinbad), 1984
  • L'Heaxagone by Christian Automatic, 1986
  • Jungle Queen by Pinball Shop, 1986 (playfield copy of Gtb Jungle Queen)


1c. Getting Started: System 1 Parts to have on-hand

Here a list of system1 parts I like to have on hand for repairs.

  • Molex 08-52-0072 crimp-on terminal pins (for single sided connectors).
  • Molex 08-52-0113 crimp-on Trifurcon terminal pins (for .156" headers).
  • Molex 26-48-1121 .156" header pins with no lock. Cut to size.
  • Molex 09-50-3121 .156" white housings. Cut to size.
  • Molex 15-04-0219 .156" polarized pegs.
  • Molex hand crimping tool for above (see here for details).
  • Molex pin removal tool #11-03-0016.
  • 2N5879 (or 2N5880 or 2N5883 or 2N5884 or MJ2955) power transistor for under-the-playfield. Another substitue for the 2n5875 is the MJ2955, which is an inexpensive alternative.
  • MPU-U45 or CEN-U45 transistors for driver board.
  • MPS-A13 transistors for driver board.
  • MPS-A70 transistors for CPU board.
  • 2N3055 (NTE130) transistor for driver board.
  • 2N6043/SE9300/TIP122/TIP102 (NTE261) transistor for driver board (just use a TIP102).
  • UDN6118 chip for score displays.
  • PMD10K40 or 2N6057 or 2N6059 transistor for the power supply.
  • UA723 or NTE923 for power supply.
  • 7404 chip for CPU board switch matrix columns and other duties.
  • 7405 chip for CPU board switch matrix rows.
  • 7408 for CPU board for score displays.
  • 7448 or 74LS48 chip for CPU board for score displays.
  • 7417 chip for CPU board.
  • 74175 or 74LS175 chip for driver board.
  • 4049 chip for CPU board.
  • 1N4004 diodes for coils.
  • 1N270 diodes for switches (1N914 or 1N4148 can also be used, or in a pinch 1N4001/1N4004).
  • 6800 to 10,000 mfd 16 volt (or higher) electrolytic cap for power supply.
  • 35 amp 200 volt lug style bridge rectifiers (for the bottom panel solenoid and CPU controlled DC voltages). Use this instead of the original (and no longer available) VARO VK438 or VL038 bridges.
  • 1k ohm trim pots for the power supply.
  • 9.1 ohm 1 watt resistors for driver board 2n3055.
  • NiWumpf system1 MPU board available from pbresource.com

See the Parts Suppliers section of this web page for places to buy these parts.


1d. Getting Started: Gottlieb System1 Introduction

    Introduction.
    Gottlieb's System1 series consists of sixteen games including Cleopatra, Sinbad, Joker Poker, Dragon, Solar Ride, Countdown, Close Encounters, Charlie's Angels, Pinball Pool, Totem, Incredible Hulk, Genie, Buck Rogers, Torch, Roller Disco, and Asteroid Annie. Up until Charlie's Angels there was also an EM version made of these games. Asteroid Annie differs from others, being a single player game (Annie was made well after Gottlieb had changed to their new System80 boardset in early 1980). The reason for this was Ed Krynski (game designer) wanted to design one more classic single player card game before he retired. A call was made to the Gottlieb service department inquiring about the number of leftover System1 CPU boards, and they made 211 games based on the 300 board available in the service department's stock.

    The System 1 technology is simple, as Gottlieb did not use solid state parts for anything that could be done with EM technology. This was unlike Bally and Williams who couldn't abandon EM hardware fast enough. In a System1 game, there are three circuit boards in the backbox: a power supply, a CPU, and a driver board. Additionally there is a sound board in the lower cabinet of games Close Encounters and later. Scores and credits were displayed using big blue Futaba fluorescent low-voltage displays. This was unlike Bally and Williams gas discharge which used 190 volt displays. This Gottlieb decision was perhaps the best one they made in regards to their solid state pinball system, as the low-voltage score displays lasted much longer and didn't require a robust power supply.

Gottlieb System 1 Joker Poker:
left: power supply, top center: CPU, bottom right: driver board.

    System1 game design was very basic, barely more sophisticated than an EM (Electro-Mechanical) pinball. There were two or four flippers, usually two slingshots, and some pop bumpers. The flippers, slingshots and pop bumpers were not solid state controlled (unlike Bally and Williams solid state pinballs). A high voltage switch closed and directly fired these devices. On slingshots and pop bumpers there was a secondary switch that was closed by the moving coil mechanics which told the CPU to score points for that device. System1 games occasionally had an eject hole and/or drop targets, which were CPU controlled. But the System 1 driver board could control only eight devices, which included three sound controls (three chimes or three inputs for a sound board), a knocker, and an outhole solenoid. That left only three CPU controlled solenoids for the rest of the game (again, perhaps a drop target reset coil and an eject hole coil!) If more than three CPU controlled coils were needed, Gottlieb could use one of the two driver board MPS-U45 lamp driver transistors as a pre-driver to an under-the-playfield mounted 2N5875 transistor (this was done as early as Joker Poker and Hulk, because of the game's abundance of drop target banks.) That meant a maximum of five game specific CPU driven coils.

    Board Naming Conventions.
    The boards in system1 games have "code names." Well that's my interpretation of it at least! Gottlieb felt this was easier to use these abbreviations, especially when labeling connectors. The schematics constantly use them, so here are the codes:

    • A1 = CPU Board
    • A2 = Power Supply
    • A3 = Driver Board
    • A4 = Scoring Displays
    • A5= Credit/Ball (Status) Display
    • A6 = In-Line Connectors
    • A7 = Sound Board (when used)

Gottlieb System 1 Countdown with ground mods and remote battery pack:
left: power supply, top center: CPU, bottom right: driver board.

Gottlieb System 1 Board layout.

    A1 Control Board (CPU Board).
    System1 was Gottlieb's first series of solid state pinballs introduced in late 1977. Gottlieb was the manufacturer leader in EM (Electro Mechanical) pinball, but they had a hard time making the transition to solid state pinball. They were also the last manufacturer of the big four (Bally, Williams, Stern, Gottlieb) to switch to solid state technology, and even made some games in both solid state and EM formats until 1979 (where the other manufacturers had abandoned the EM pinball format since 1977.) Bally and Williams had been working on solid state architecture since about 1975, and fully adopted the technology by early 1977.

    Gottlieb had hired a new young electrical engineer to help develop their own solid state pinball hardware. Yet after about 6 months on the job, their new employee quit. This put Gottlieb in a bad situation - time was already working against them, and they no longer had an electrical engineer working on their new solid state board system. Being in a pinch, Gottlieb hired Rockwell to design their solid state pinball boardsets (although a bid was sent to National Semi-Conductor too, Rockwell was chosen because of their ability to supply all chips and boards, and a system to program the game chips.) Again they were already behind in this new solid state pinball race, thus making them the last to enter the solid state market. This was a mistake that Gottlieb endured for many years, as Rockwell did not serve Gottlieb well. Gottlieb went from being the premier (EM) pinball maker, to being in last place for many operators. While all the other pinball manufacturers used the 68xx series of micro-processors on their boardsets, Gottlieb used something different. This meant different parts and different service techniques. The whole Gottlieb system was different in so many ways, making them the odd man on the block. Why own a Gottlieb solid state game when you could buy a Stern or Bally, and move boards back and forth between games? Heck, even Williams used the 68xx series of chips like Bally/Stern. Commonality meant a savings in parts and money. Yet here's Gottlieb, different, and with early solid state reliability problems which they just couldn't shake.

    Interestingly, Gottlieb did make some System1 titles in EM format too, but in much smaller numbers. The EM versus SS (solid state) games had generally the same rules, but the solid state versions could go to 5x bonus and 999,990 point scoring (where the EM versions were limited to 199,990 points.) The system1 titles that were also made in EM format included Joker Poker (EM version only going to 2x bonus), Cleopatra (both EM and SS made with identical rules using 2x bonus max), Close Encounters of the Third Kind (EM version only going to 3x bonus), Charlie's Angles (EM version only going to 3x bonus), Sinbad (EM version only going to 2x bonus), Solar Ride (EM version only going to 1x bonus), Count Down (EM version only going to 3x bonus), and Dragon (EM version only going to 2x bonus.)

Gottlieb System 1 CPU board from a Joker Poker. The red wire at the left is for the
ground modifications.

    The control system designed by Rockwell used their PPS-4/2 (Pinball Playing System 4 Bit) system. One problem was the Gottlieb board system did not test itself at power-on (like the Bally/Stern MPU boards.) The Gottlieb CPU had no way to tell the user of any errors (there was no CPU board LED flash sequence.) This led to operator frustration in repair. Gottlieb also had ground and connector issues from the start, a problem that Bally, Stern, and Williams did not have.

    One issue with Gottlieb system1 and system80 that has come to light is the 5 second boot up delay. Here we all thought the board was checking itself for problems, like the Bally/Stern MPU board, but Gottlieb/Rockwell just forgot to add a diagnostic LED. As it turns out, that 5 second boot up delay is just a farce. It's a delay, and nothing more. This delay made you think the boardset was checking itself, when in fact it was just a 5 second delay loop in the code. Why do that? Because again, Rockwell wanted to make it look like the Gottlieb system1/system80 board set was actually doing some testing (when in fact it wasn't.)

    The Rockwell PPS-4/1 and PSS-4/2 system was a 4-bit parallel processing system with two CPU "spider" chips that communicate with each other (U1 11660-CF was the main processor, and U2 10696-EE was the second processor). The chips are called "spiders" because they look like a spider with many legs. The spider chips were a wider chip package, almost a square chip. System 1 used six of these custom spider chips labeled U1 to U6: two for the CPU (U1/U2) and one each for the switch matrix (U5 A1752-CF), solenoid control (U4 A1753-CE), and score displays (U6 10788-PA). The last spider chip (U3, also a 10696-EE chip, same as the second CPU processor at U2) was used for lamps and a few switches and left over duties. Both the switch matrix (U5, A1752-CF) and solenoid control (U4, A1753-CE) spider chips have built-in ROM software. Display output was controlled by the U6 spider chip (10788-PA). The switch matrix has eight rows (R0-R7) and five columns (S0-S4), for a total of 40 switches. These are all driven by chips Z8 (strobes/columns, 7404) and Z9/Z28 (rows, 7405.)

Two System 1 CPU board spider chips and the game PROM ("C" means Joker Poker).
The added red wire to cap C16 negative lead is part of the ground modifications.

    The solenoid control (U4, A1753-CE) and switch matrix (U5, A1752-CF) spider chips are notorious for easily failing. The solenoid control spider dies from locked on coils due to driver transistor failure. The switch matrix spider dies from coil voltage being shorted to the switch matrix. The two CPU spiders (U1 11660-CF and U2 10696-EE), the display spider (U6, 10788-PA) and the U3 (10696-EE) spider rarely fail. Unfortunately none of the spider chips are available, hence replacement CPU board have been created by Ni-Wumpf and Pascal Janin).

    Here's a summary of the spider chips:

    • U1, 11660-CF (CPU)
    • U2, 10696-EE (CPU)
    • U3, 10696-EE (misc lamps and switches). Same as U2 spider
    • U4, A1753-CC,CE,EE (solenoids, often fails)*
    • U5, A1752-CD,CF,EF (switch matrix, often fails)*
    • U6, 10788-PA (display)

    * Note that spider chips U4 or U5 contain the game operating system ROM, and must be of the same revision. These are the two spiders that fail the most. The revision levels that work together are:

    • U4 A1753-CC works with U5 A1752-CD
    • U4 A1753-CE works with U5 A1752-CF
    • U4 A1753-EE works with U5 A1752-EF

    Here's a summary of the CPU board connectors:

    • J1 (left): +5 volts, -12 volts, ground (CPU board power)
    • J2 (top right): score display segment control
    • J3 (lower right): score display digits strobes
    • J4 (bottom right): not used on any system1 game
    • J5 (bottom center): data/address bus, +5 volt/ground to driver board
    • J6 (bottom left): switch matrix lines for coin door
    • J7 (bottom far left): switch matrix lines for playfield

    The CPU board keeps high scores and audits in a 5101 RAM (at Z22), which maintained power using a NiCad "Data Sentry" battery (though some System1 CPU boards used a Bally-style AA sized NiCad). These batteries die and leak their corrosive liquids easily, causing much CPU board and connector damage. The game PROMs (where the game specific rulesets are stored) are masked ROMs and the blanks and the equipment to program them is generally not available. PROMs were identified by letters from "A" to "R", including a "T" test PROM. There are EPROM replacement boards that plug into this PROM's socket to solve this problem.

    On the CPU board, always check TC3 (test connector three) jumper plug, as it carries -12 volts to the CPU board, which is required by the CPU spider chips and the coil drive circuit. Also the 5101 RAM easily fails. Any weird problems with high score and the 5101 RAM is probably bad. The self test circuit for the RAM is highly suspect and often passes a bad RAM. TC1 and TC2 can be ignored as they are used for internal factory testing. If these fail they do not affect anything. Switch 25 (red button switch at top of board) is the high score and audit reset only.

A NiWumpf System 1 replacement CPU board. The blue line in the upper
left hand corner is the ground trace used for the ground modifications.

    There are also two after-market CPU boards available for Gottlieb System 1 games. The most popular is the Ni-Wumpf board, made in Rochester NY. Available for about $180 from pbresource.com and has a DIP switch allowing it to be used in any Gottlieb System 1 game. The Ni-Wumpf CPU board is about half the size of the original Gottlieb System 1 CPU board. Dave (the creator) re-wrote the program code for all the Gottlieb System 1 games and put it in a single EPROM on his Ni-Wumpf board. The advantage to this is he can maintain and change the code as he sees fits, and run it in a different processor chip. The downside is some games have slightly different rules. Dave also added some excellent diagnostic tools to his board which are far better than the Gottlieb diagnostics. The Ni-Wumpf system1 CPU board is an excellent value especially if your CPU board has problems with battery corrosion and/or the spider chips.

Pascal Janin's Pi-1 System1 replacement CPU board.

    The other CPU board is by Pascal Janin of France and is called the Pi-1 (for about $175). This board also is about half the size of the original Gottlieb System 1 board. Pascal's board more closely emulates the original Gottlieb game rules, but Pascal also added some additional features like skill shots (which none of the original System 1 games had). The Pi-1 board is set to the proper system1 game through software after the board is booted the first time. Pascal has also a version called the Pi-1 X4, which combines the CPU, driver, power supply and the 2nd generation sound board in one single board (for about $380). All you have to do is make sure the game's connectors and any under-the-playfield transistors (where applicable) are good, and the game is electronically all ready to play. Both the Pi-1 and Pi-1 X4 are now readily available only from Pascal directly.

The Pi-1 X4 combo System1 replacement CPU/Driver/Power Supply/Sound board.

    A3 Driver Board.
    The System 1 driver board could control only eight devices, which included three sound controls (three chimes or three inputs for a sound board), a knocker, and an outhole solenoid. That left only three CPU controlled solenoids for the rest of the game (again, perhaps a drop target reset coil and an eject hole coil)! The sound controls, knocker, outhole are the five "dedicated" solenoids, because they don't change from game to game. The three left over solenoids 6,7,8 are non-dedicated, and vary from game to game. Though it should be noted that solenoid8 is usually for big devices like a drop target reset coil because it uses Q29 (MPS-U45) and the large Q45 (2n3055) as its drive chain. Also there are two MPS-U45 transistors used to drive the two under the playfield relays (Tilt and Game Over.)

    Driver Board Transistor Overview
    Coil# Description Transitor# Notes
    1 Outhole Q32 (2n6043) Dedicated
    2 Knocker Q25 (2n6043) Dedicated
    3 10pt Chime Q26 (2n6043) Dedicated
    4 100pt Chime Q27 (2n6043) Dedicated
    5 1000pt Chime Q28 (2n6043) Dedicated
    6 Game dependant Q31 (2n6043)  
    7 Game dependant Q30 (2n6043)  
    8 Game dependant Q29, Q45
    (mps-u45,
    2n3055)
     

The Rottendog replacement Gottlieb System 1 driver board. The cool thing
about this board is the updated design. The Dawg people updated the
driver board so it uses one common MOSfet driver for all the coils and
lamps. The MOSfets are rated to handle way more current than the original
Gottlieb components, so it is unlikely you'll ever have to repair this board.
Price is very reasonable too.

The Gottlieb System 1 driver board. The wire at the upper right
is the connection mod used for the ground modifications.

    The knocker, three chime coils, outhole, and solenoid #6 and #7 were all controlled by 2N6043 transistors (can be replaced with TIP102). In addition there was a large 2N3055 transistor at Q45 for solenoid #8 (pre-driven by Q29 MPS-U45 to the left of it), which could be used for a large drop target reset bank coil. This meant the game only had these three driver board transistors for game-specific coils. If the game needed to drive any more coils, lamp driver transistors could be used as a pre-driver to an under-the-playfield mounted 2N5875 transistor. This meant there could only be a total of five game specific unique CPU controlled coils (using a maximum of two under-the-playfield transistors.) But on the other hand remember the slingshots and pop bumpers are not CPU controlled and instead use direct switches. Also another interesting fact is the coin door lockout coil is not CPU controlled at all. It instead is directly connected to 28 volts and is energized whenever the game is turned on. (It's purpose is to return a coin to the user if inserted when the game was off.)

    Here's a summary of the driver board connectors:

    • J1 (top): data/address bus, +5 volt/ground from CPU board
    • J2 (far right): Q25-Q28 solenoid control
    • J3 (middle right): Q19-Q44 lamp control
    • J4 (middle left): Q29-Q32,Q45 solenoid control
    • J5 (far left): Q6-Q17 lamp control, Q1-Q4 solenoid control

    There was no lamp matrix, as each CPU controlled playfield lamp was driven by one of the 36 lamp transistors. Lamps L1-L4 used a MPS-U45 (note two of these U45s were used for the Game Over and Tilt relays, which in turn controlled a lamp.) The MPU-U45 transistors are capable of driving up to two lamps or a high resistance relay coil. The rest of the lamp drives L5-L36 used the smaller MPS-A13 transistor (which could only drive a single bulb.) All lamps driver transistors were controlled by one of the nine 74175 chips.

The Gottlieb System 1 driver board transistor layout.

    There are also two under-the-playfield relays that are driver board driven. These two relays are the Q (Game Over) and T (Tilt) relays. These are driven by Q1 and Q2 respectively.

    Under Playfield Mounted Transistors (Extension of the Driver board).
    Some system1 games used one or two of the 36 driver board MPS-A13 lamp transistors to control additional playfield solenoids. The low-voltage (6 volt) lamp transistors were wired to under-the-playfield mounted 2n5875 power transistors, which drove a hi-power 24 volt solenoid. Essentially the MPS-A13 lamp driver transistor was a pre-driver for the larger under playfield mounted 2n5875 transistor, which ultimately drove a coil. These playfield mounted transistors added another level of complexity to the System1 design, and often confused operators. Also to make things even more confusing sometimes Gottlieb used Solenoid6 or Solenoid7 (larger 2n6043 transistors) as pre-drivers for an underplayfield transistor, in the case of a high powered/low ohm coil. More information can be seen in the under the playfield transistors section. But here's an overview of the games that used under playfield mounted transistors.

    Games with Under the Playfield Transistors
    Game Coil Designator Pre-Driver PF Driver
    Close Encounters Roto Target Sol.7 (Q30) 2n6043 2n5875
    Count Down Yellow drop target bank L17 (Q17) MPS-A13 2n5875
    Blue drop target bank L18 (Q18) MPS-A13 2n5875
    Hulk Left Shooter Sol.6 (Q31) 2n6043 2n5875
    Right Shooter Sol.7 (Q30) 2n6043 2n5875
    Joker Poker Kings drop target bank L17 (Q17) MPS-A13 2n5875
    Pinball Pool Left drop target bank L17 (Q17) MPS-A13 2n5875
    Roller Disco Left drop target bank Sol.7 (Q30) 2n6043 2n5875
    Torch Left drop target bank Sol.6 (Q31) 2n6043 2n5875
    Asteriod Annie Left drop target bank Sol.7 (Q30) 2n6043 2n5875
    Buck Rogers Vari-Target L17 (Q17) MPS-A13 TIP115

An under the playfield 2N5875 transistor.

Schematic on Countdown for its two under-the-playfield 2N5875 transistors.
From actual Gottlieb documents, so it's their property.

    A2 Power Supply.
    The system1 power supply gets power directly from the transformer at the bottom of the cabinet. It consists of rectifiers and regulators to create the various output voltages of +5V, -12V, +8V, +4V, +60V and +42V. Rottendog Amusements makes an excellent replacement System1 power supply for about $65. An excellent value, the Rottendog P.S. works great and is plug & play. Also Great Plains Electronics (GPE) has a really nice replacement System1 power supply.

Original Gottlieb System 1 power supply board mounted in its metal "L" frame.
The original filter capacitor on this example needs to be replaced.

Another generation of the original Gottlieb System 1 power supply
board mounted in its metal "L" frame. This one had some modifications
like the original 2900 mfd 12 volt filter capacitor was replaced with
a new 10,000 mfd cap. Also an added LED (blue arrow) for 60 volts.

The Rottendog replacement Gottlieb System 1 power supply board.

The GPE replacement Gottlieb System 1 power supply board.

    Bottom Panel.
    The bottom panel in the lower cabinet of a System1 pinball houses the two main power transformers, the main fuse bank, the copper ground bank (where all ground wires originate), the RF filter and auxiliary 120 volt service jack, a bank of four diodes (for the coin door switches), and two bridge rectifiers (one for the 24 volt solenoids and the other for the 6 volt CPU controlled lamps).

The Gottlieb System1 bottom panel.

    Relays.
    Every System1 pinball has two relays mounted under the playfield. These are the Game Over Relay (Q), and the Tilt Relay (T). The Game Over relay activates and stays energized all during a game. This turns the 24 volt power on for the flippers, pop bumpers and slingshot coils. It also turns off the Game-Over light in the backglass. On Bally, Stern, and Williams games this relay is on the solenoid driver board, and has a plastic cover to protect it. But Gottlieb felt it should be more accessible (or they had a large stock of old EM relays), and mounted their Game-Over relay (or flipper relay as Bally/Williams calls it) under the playfield. The advantage to this is the relay is more accessible, but it's also more easily damaged or knocked out of alignment or the switches mishandled.

    The T-relay is the tilt relay. This comes on when the game is tilted, and stays energzied until the current ball is drained into the outhole. This relay disables the power to the coils and flippers, and turns off the computer controlled lighting power to the game. It also turns on the Tilt light in the backglass. Why Gottlieb used a Tilt relay is unknown. No other manufacturer had a Tilt relay - they controlled tilts through the software and the Game-Over (aka Flipper) relay. (Again another Gottlieb oddity.)

The Gottlieb System1 T (Tilt) and Q (Game Over) relays.

    System1 Score Displays (1A4-4A4 and A5.)
    Another Gottlieb difference was the use of florescent Futaba score displays. Other manufacturers used orange gas-plasma displays running at -100 and +100 volts. Gottlieb took another approach and used blue florescent displays running at 60 volts (or 42 volts for the smaller A5 credit/ball display.) Personally I've seen problems with both kinds of displays, so there's really no advantage or disadvantage to Gottlieb's choice of displays, except it was "different." (Both styles of score displays wear out or have logic problems.)

The Gottlieb blue Futaba credit/ball display running at 42 volts.

    System1 Grounds (a Big Problem.)
    Unlike all the other pinball manufacturers, Gottlieb used a different system to ground their electronics boards. All other makers had a metal backbox ground plane, with all the boards bolted to this metal backbox plate. This ensured all boards had the same ground. Gottlieb too had a metal backbox ground plate, but mounted all their boards off this plate using nylon stand offs. This meant that each board had ground "daisy chained" to it via a wire and a connector. If these ground connectors gained resistance or failed (and they often did due to battery corrosion and wear), the backbox electronic boards could have slightly different levels of "ground." This varying ground caused all sorts of reliability issues on Gottlieb system1 (and system80) games. For example, playfield coils or CPU controlled lamps could just lock-on for no apparent reason due to ground differences between the CPU and Driver boards. All it took was one connector failure in the ground daisy chain, and the game could fail in a cloud of smoke. We will talk more about this later, and how to solve this problem.

    System1 Sounds (Chimes and A7 Boards.)
    In the three first System1 games there was a three tone chime unit, as used in Gottlieb's EM games. With Close Encounters this changed to a simple tone generator sound board (aka the "Chime Board"), which still used the same three driver board transistors to generate sound. The Gottlieb system1 sound board was located in the lower cabinet right next to the knocker (where the chime box was previously mounted.)

Gottlieb System1 Game Sounds
Game Date Type of Sound CPU ROM Sound ROM
Cleopatra 11-1977 Chimes A or 409 ROM none
Sinbad 05-1978 Chimes B ROM none
Joker Poker 06-1978 Chimes C ROM none
Close Encounters 10-1978 Electronic Chime Board C ROM none
Dragon 10-1978 Electronic Chime Board D ROM none
Charlies Angles 11-1978 Electronic Chime Board H ROM none
Solar Ride 02-1979 Electronic Chime Board E ROM none
Count Down 05-1979 Electronic Chime Board F ROM none
Pinball Pool 08-1979 Electronic Chime Board I ROM none
Totem 10-1979 Multi Sound Board J ROM J-Snd ROM
Incredible Hulk 10-1979 Multi Sound Board K ROM K-Snd ROM
Genie 11-1979 Multi Sound Board L ROM L-Snd ROM
Buck Rogers 01-1980 Multi Sound Board N ROM N-Snd ROM
Torch 02-1980 Multi Sound Board P ROM P-Snd ROM
Roller Disco 02-1980 Multi Sound Board R ROM R-Snd ROM
Astroid Annie and the Aliens 12-1980 Multi Sound Board S ROM S-Snd ROM

The Gottlieb System1 first generation 3-tone sound board (Close Encounters)
with the small blue volume control.

The Gottlieb System1 first generation 3-tone sound board (Close Encounters).

The Gottlieb System1 first generation 3-tone sound board (Countdown).

    Sound improvement came with Totem, when a microprocessor controlled sound board replaced the earlier 3-tone sound board. (Both the chime box or the sound boards were located in the same place, in the right side of lower cabinet.) The new sound board as used on Totem and later games (multi-mode sound), though having more sounds, was not really a big sound improvement for the System1. It had a switch that changed the sound format, much like Williams did. It also used a now unavailable Rockwell chip R3272-12. It still used the same three driver transistors from the driver board, but not in unison (as Williams and Bally did to control more than three different tones). Instead Gottlieb's MPU controlled sound board randomly picked the different sounds to play. This caused some player confusion, because a 10 point switch could have any number of different sounds.


1e. Getting Started: Summary of Mandatory System1 Modifications

    Gottlieb System1 pinball games will need some *mandatory* things done to them to make them a reliable system. This is a summary of what is involved, to give you an idea of what work you have cut out for yourself.

    1. Replace the 5/12 volt Power Supply filter capacitor.
      The original 2900 (or 4700) mfd filter cap on the power supply MUST be replaced with a new 6800 to 10,000 mfd capacitor. This ensures a good smooth 5 volt main power for the CPU and driver boards. If you replaced the power supply with a Rottendog or GPE version, you can skip this step.

    2. Ground modifications.
      Much like Gottlieb's System80 pinballs, System1 games also need to have ground modifications to the power supply, CPU board and Driver boards. This ensures reliable operation and coils that don't lock-on and destroy driver board and CPU boards. And if you have a Rottendog power supply, just use the power supply "L" frame as the central ground point (the Rottendog power supply is already modified so it brings ground to the "L" frame.)

    3. Remove the original CPU board Battery.
      If running with an original Gottlieb CPU board, the original memory backup battery MUST be removed (and discarded). System1 pinballs will run fine with a remote "AA" battery pack to maintain credits and high scores. Make sure to use a 1N4004 blocking diode with the "AA" battery pack so the CPU board does not try and recharge the "AA" batteries.

    4. Check for CPU board Battery Corrosion.
      If the original CPU board memory backup battery has been left on the CPU board, chances are good it has leaked and corroded the board (this is why we remove the battery!) If corrosion has happened, this will need to be cleaned up (sanded clean or bead blasted) and then neutralized with white vinegar and then water and then alcohol. Or the entire CPU board replaced with a new Ni-Wumpf or Pascal Janin CPU board.

    5. Replace Connector Pins.
      The .156" Molex single sided edge connector pins used to mount connectors to the power supply, CPU board and driver board most certainly will need to be replaced (especially if there was *any* battery corrosion on the CPU board). Most certainly the CPU board's bottom edge J7, J6 and J5 connector pins will need to be replaced. Also the driver board's top edge J1 connector pins probably too.


1f. Getting Started: Gottlib System1 Overview video

    This 7 minute movie explains the Gottlieb System1 solid state pinball system and it's electronic parts.



2a. Before Turning the Game On: Check the Coil Resistance & Common Coils.
    A very good idea for any unknown game just purchased is to check all the coils' resistance. If the game is new to you, and you have not powered it on, a quick check of coil resistance will tell you a lot about your new game. This takes about one minute and can save you hours of repair and diagnosing work.

    Any coil that has locked on (usually due to a short solenoid driver board transistor) will heat up and have a lower total resistance. This happens because the painted enamel insulation on the coil's wire burns, causing the windings to short against each other. This will lower the coil's resistance, causing the coil to get even hotter. Within a minute or so the coil becomes a dead short (less than 2 ohms), and usually blows a fuse.

    If the solenoid driver board (SDB) or under-the-playfield mounted transistor is repaired, and the game is powered on with a dead-shorted coil, this will blow the same driver transistor(s) again when the coil is fired by the game for the first time! There is no sense making more work for yourself. So take 60 seconds and check all the coils' resistance BEFORE powering the game on for the first time.

Checking a slingshot coil's resistance with a DMM. The 3.4 ohm reading is fine
for the A-1496 slingshot coil.

    In order to check coil resistance, put your DMM on its lowest resistance setting. Then put the DMM's red and black leads on each coil's lugs. A resistance of 2 ohms or greater should be seen.

    If there is anything less than 2 ohms, then remove the GROUND wire (the wire connecting to the non-banded diode coil lug), and retest the coil. If the coil resistance is no longer low, the driver board has a bad driving transistor for this coil (replace the under-the-playfield mounted transistor {if used}, driver board transistor, and pre-driver transistor.) If the coil resistance is still low, cut the diode off the coil and re-test the coil. If the coil resistance is normal, the diode was bad (install a new 1N4004 diode.) If the coil resistance is still low, the coil itself is bad. Replace the coil with a new one, and make sure there is a 1N4004 diode installed across the coil's lugs. Remember when reconnecting the wires to the coil that the power wire (usually two wires or thicker wires) goes to the coil's lug with the BANDED side of the diode attached. The thinner wire is the coil's return path to ground via the driver transistor and attaches to the coil lug with the non-banded side of the diode attached.

    If a low resistance coil is found, also suspect the associated driver board (or under-the-playfield mounted transistor if used) as bad. A low resistance coil is a red flag, a warning, that there may be problems on the driver board or with an under-the-playfield mounted driver transistor. Actually with System1 games, if a low resistance coil is found, I can pretty much guarantee that you will need to (should) replace, of course, not only the coil and coil diode, but also all the silicon devices in its ground path. This includes the under-the-playfield transistor {if used}, driver transistor on driver board, and any pre-driver transistor. I would also check the 74175 chip on the driver board (using a DMM set to diode setting), which drives the transistors, if any of the driver transistors were bad/replaced. See the Locked-on or Not Working Coil section of this document for more info.

    Common Coils Used.
    Here's a list of common coils used and their resistance. Remember all coils (relay or otherwise) should have a 1n4004 diode with the power line attached to the coil lug with the banded side of the diode.

    • A-17875 - Flipper coil, 2.8 ohms (power) and 40 ohms (hold)
    • A-1496 - Pop bumper, 3 ohms
    • A-5194 - Slingshot Kicker, Pop Bumper, 4.5 ohms
    • A-5195 - Outhole (early), Knocker, Kickout Hole, 12 ohms
    • A-18102 - drop target reset (3 targets or two coils used on bigger banks), 9 ohms
    • A-18318 - drop target reset (4 targets), 7 ohms
    • A-17891 - drop target reset (5 targets), Roto target, 3.5 ohms
    • A-16570 - Outhole (later), Kickout Hole, 15 ohms
    • A-16890 - Game over relay, Tilt relay, coin lock out relay, 230 ohms
    • A-17564 - Vari-Target Reset relay, 50 ohms
    • A-17876 - Chimes, 24 ohms


2b. Before Powering On: The Power Train and the Power Supply (Repair/Upgrade)

    This section will "start at the beginning" and show how power gets from the wall outlet to the game. It will also describe what typically goes wrong in the power train and how to fix it. Also many of the fixes and upgrades in this section are mandatory for proper long-term operation of a System1 power supply.

Bottom Panel - Where is all Starts.

    The bottom panel (lower cabinet) is where the power all starts. The line cord comes into the game and goes to line filter. Next it goes to a line fuse (and an outlet plug), and then to the pair of transformers. Note Gottlieb does not use a MOV on the line filter (unlike Bally and Williams), so there is no surge protection in system1 games.

    The two transformers convert the 120 volts AC input to other voltages needed for the game. The large transformer outputs power for the solenoids (24 volts), general illumination light power (6.3 volts), and CPU controlled light power (6 volts). The small transformer outputs the main score display voltage (60/42 volts), the computer board voltage (12 volts which ultimately ends up as +5 volts), and the score display offset/reference voltages (8 and 4 volts).

The Gottlieb System1 bottom panel. The power supply path starts in the lower cabinet
on this "bottom panel".

    The transformer outputs only AC voltages, but the game largely uses DC volts. So some voltages go to bridge rectifiers or power supply diodes that convert the AC to DC volts. There are two bridge rectifiers on the bottom panel, all being 35 amp 400 volt lug style bridges:
    • 6 volt bridge which is used for the CPU controlled lighting.
    • 24 volt bridge which is used for the playfield coil voltage.

    After the power is converted from AC to DC via these three bridge rectifiers, it goes through bottom panel mounted fuses. Also the voltages that don't get converted to DC on the bottom panel also go through fuses on the bottom panel:

    • backbox 6.3 volts AC general illumination
    • playfield 6.3 volts AC general illumination
    • CPU controlled 8 volt DC lights
    • Coil power 25 volts DC
    • Score display 69 volts AC

    There are other system1 fuses beside the bottom board fuses, all mounted under the playfield. There is usually a fuse for the pop bumpers and other major coil items like drop target reset banks.

    My advice for fuses is simple: test EVERY fuse in the game by removing it and using a DMM (digital multi-meter) set to continuity. Don't try and give fuses a visual test! And I highly recommend removing the fuse from the fuse holder for testing, as this will show a fuse that is cracked or a fuse holder that is bad (and there are far less "false reading" testing a fuse out of circuit.) Obviously this is all done with the power off.

    Note many under the playfield fuses will not have their fuse value stated with a label. Many fuses will, but others will not (or the label fell off). For this reason it's a good idea to get a game manual. Do NOT over fuse! If it says "2 amp slow-blow", then that's what you should use. The fuses are there for a reason, to be the "weakest link". If over-fused, much more expensive items become the weakest link (like driver transistors and/or coils). So use the correct fuses.

Blown Fuses and Bridge Rectifiers.

    Fuses are designed as the weakest link in the chain. Fuse tend to blow for a reason, but they can "just die" due to fatigue and age. Yet for the most part, if a fuse is blown on the bottom panel there's usually a reason, like a shorted bridge rectifier. This is a common problem especially for the CPU controlled lights' 6 volt bridge, but the solenoid bridge can also short (causing its associated fuse to blow). For this reason, it's a good idea to test the bridges to make sure they are not shorted.

Testing a bridge with a DMM set to the diode function, and putting the red DMM
lead on the ground (green) bridge lug. This bridge is testing "good".

    Testing a Bridge Rectifier with a DMM.
    To test a bridge a DMM (digital multi-meter) is needed. Set the DMM to diode test, and the first step is to put the red DMM lead on the ground lug of the bridge. (On system1 games the ground lug is easy to find, as it's the one with the green wire attached.) Then put the black DMM lead on each of the bridge lugs next to the ground lug (the AC bridge lugs.) A value of .4 to .6 volts should be seen on the DMM. Anything outside that range indicates a bad bridge rectifier.

Testing a bridge with a DMM set to the diode function, and putting the black DMM
lead on the positive output bridge lug. This bridge is testing "good".

    For step two of the test, put the black DMM lead on the positive output of the bridge. This is again easy to find as it's the bridge lead diagonal to the ground lug. (Also on newer bridges the positive output lug is set 90 degrees off from the other three lugs.) Then put the red DMM lead on each of the bridge lugs adjacent to the positive output lug (again the AC bridge lugs.) A value of .4 to .6 volts should be seen on the DMM. Anything outside that range indicates a bad bridge rectifier.

    If a bad bridge is found, replace it with a new 35 amp 400 volt bridge with lugs. These are inexpensive and easy to get from a variety of electronic parts houses.

    To summarize, to test a bridge rectifier, do this:

    1. Put the DMM on diode setting.
    2. Put the black lead of the DMM on the "+" (positive) terminal of the bridge.
    3. Put the red lead of the DMM on either AC bridge terminal. Between .4 and .6 volts should be seen. Switch the red DMM lead to the other AC bridge terminal, and again .4 to .6 volts should be seen.
    4. Put the red lead of the DMM on the "-" (negative) terminal of the bridge.
    5. Put the black lead of the DMM on either AC bridge terminal. Between .4 and .6 volts should be seen. Switch the black DMM lead to the other AC bridge terminal, and again .4 to .6 volts should be seen.

    An interesting note on the system1 power train bottom board - there is NO bridge rectifier for the 5/12 volt power. This is instead handled by the power supply board itself using a pair of 3 amp (3a100 or 1n5401) CR1/CR2 diodes. That means the +5/12 volts DC is only half-wave rectified and not full wave rectified. In addition the filter cap is only 2900 mfd. You would think this would provide a rather rippled +5/12 volts (which it does). For this reason you will need to replace the 2900 mfd power supply cap C1 with higher 6800 to 10,000 mfd version. This "problem" was dramatically improved with Gottlieb's later system80 games, where a full wave bridge rectifier was added to the bottom board for the 5/12 volts, and its filter capacitor was increases in MFD rating.

Under Playfield Relays.

    Mounted under the playfield are two relays. This is much like what Gottlieb did on their later system80 games, and is much unlike what other manufacturers did.

    First is the Tilt "T" relay, which pulls in when the game is tilted. When energized at a tilt, this turns on the "tilt" light in the backbox, turns off the GI (general illumination) lights on the playfield, and turns off the power to all the coils on the playfield. If a ball is tilted during play, the ball will immediately drain (since there's no flipper or coil power). Once the ball hits the outhole switch, the CPU board will de-energize the Tilt relay, and the game continues.

The Game Over "Q" relay and Tilt "T" relay under the playfield.

    The other relay is the Game Over "Q" relay. This relay energizes when a game is started, and turns on the power to all the coils on the playfield. All other manufacturers mounted their game over (aka flipper relay) to the CPU or driver board, but Gottlieb mounted theirs under the playfield (a leftover from the EM era).

    As a diagnosing feature, with the game on and in "attract" mode (ready to take money and start a game), the Game Over "Q" relay can be manually held in (assuming you're careful and don't knock the relay's activation plate off it's mounting pivot point). This will turn all the power on to the flippers, pop bumpers, slingshots without having to start a game. This is handy when adjusting and testing these devices.

Slam Switch (Coin Door) and Tilt Switches.

    Another unusual thing about Gottlieb is their coin door "slam" switch. This normally closed switch MUST be closed or a game won't start (heck the CPU board won't even really "boot" either). Unlike the other pinball manufacturers where their slam switch was normally open, Gottlieb (foolishly) choose to have their slam switch normally closed. This means if this switch is open, or the connectors/wiring from the CPU board to this switch are broken/corroded/failed, the game will NOT work! This is important to know as it's different than other pinball makers.

The coin door showing the normally closed Slam switch.

    In addition to the slam switch, there is the ball roll tilt (just inside the coin door area.) This is a Normally CLOSED style tilt (unlike System80 games that used normally open), just like the coin door Slam switch. This is important to remember as the game will NOT work if the ball roll tilt switch is open. That is, if the game is turned on with the ball roll tilt switch open, it exhibits the same behavior as an open coin door Slam switch (blue score displays come on immediately with slight scrolling, no five second delay.) A common reason for this is a broken green wire going to the ball roll tilt switch - the slip lug for the wire breaks, so the wire is no longer connected to the switch. A quick soldering of the wire to the switch lug fixes this problem.

The ball roll and pendulum tilt switches on a system1 game. The
ball roll tilt switch must be CLOSED for the game to even "boot".

    There are of course "normal" tilt switches in system1 games too. like the pendulum tilt, which is typical of all pinball games (this is a normally open tilt switch). There are also some weighted tilt switches mounted in other places. Usually one or two under the playfield for example. These get far less mangled than the ball roll and pendulum tilts (mostly because when a game is moved, the ball roll/pendulum can easily get jammed.)

Power Supply Board Overview.

    The Gottlieb System 1 power supply is a fairly robust device. But it certainly is not perfect. Heck it's not easy to work on either. In order to get to the solder side of the board (to remove any suspect components), the power supply must be "taken apart". This means removing four corner machine screws, then two machine screws used as heat sink screws for the outside edge TIP31's, remove two more machine screws for the Q1 transistor, and then desoldering the Q1 transistor. Wow that's a lot of work! And then after you think it's all fixed, you have to at least solder the Q1 transistor back and test the board. If you did well, then re-assemble the whole thing. It's a fair amount work. This is why many people just spent the $70 and buy the new replacment Rottendog Amusements power supply (which by the way is a good product) or the new Great Plains Electronics (GPE) system1 power supply (again, another great product).

    One problem with power supply is the -12 volts. If this supply is missing (it feeds only to the CPU board), the system1 game will power on with all the coils and most of the CPU controlled lamps "locked on". This is definitely a bad thing, but should be kept in mind.

    Another problem is the +5 volt DC rectifying transistor Q1, which makes the whole board to get quite warm because it is attached to Q1's heatsink. After about 30 to 60 minutes, the entire power supply "L" aluminum frame (which is the heat sink for Q1, and which the entire power supply board is mounted) gets quite warm. This eventually causes the large C1 +5/12 volt filter capacitor (replace with 6800 to 10,000 mfd 20 volts) to dry out. This can cause strange problems and game lockups, or even damage to the CPU board. Sometimes even the Q1 transistor can fail. The original PMD12K40 transistor is hard to find, but if can be replaced with a 2N6057 or 2N6059.

    There is also another large filter capacitor at C6 (200 mfd 150 volts) used for filtering the score display voltage. When this cap dries out this causes the displays to flicker or go dim.

    Another common problem are the two trimmer potentiometers begin to fail because of dust, causing overvoltage or other problems. The trimmers can be cleaned with contact cleaner or preferably replace them with new ones. There are two pots, R4 to adjust the +5 volts (1k ohms) and another R16 (1k ohms) to adjust the +60 volts for the score displays.

    Rectifier diodes CR1 and CR2 (1N5401 3amp 100v) are underrated too. It is good to replace those with at least 4A diodes.

    J1 Power Supply Connector Warning.
    A common failure in these boards is misconnection of connector J1. The connector is removed when backbox is taken off, and when replacing it is possible for the connector to be installed upside down! There is a "This Side Up" sticker on the connector housing, but it may have fallen off. Pay attention when installing this connector as an upside down J1 power supply connector will ruin the power supply board, make the bottom board small transformer turn red hot until it burns like a fuse, and could damage the CPU board too (the power supply crowbar circuit *should* save the CPU board, but don't bet on it). Hint: the green ground wire on this connector goes to the left as facing the power supply board.

    Replace the Power Supply's C1 5/12 volt Filter Cap NOW.
    The power supply takes 11.5 volts AC at connector A2P1 pins 1,2 and goes through two 3amp 100 volt diodes (1N5401) at CR1 and CR2 to convert this voltage to 12 volts DC. Then a 2900 (or 4700) mfd electrolytic filter capacitor at C1 smooths this voltage. Then the voltage is rectified to 5 volts through IC1 (UA723) and Q1 (PMD10K40 or 2N6059), which supplies the main 5 volt power for the CPU and driver boards.

The Gottlieb System 1 power supply board mounted in its metal "L" frame.

    Unfortunately C1 at 2900 mfd (or 4700 mfd) is way too small of a filter cap, and the fact that this cap is 30 years old isn't helping things either. Replace this cap with a new 6800 mfd to 10,000 mfd 16 volt or higher filter capacitor.

    When replacing this capacitor it is NOT necessary to take the whole power supply apart! Just cut of the old capacitor off the power supply board, leaving the old cap leads as long as possible. The new filter capacitor will no doubt be much smaller (isn't everything made smaller today?), so just tie the new capacitor to the old cap's leads. The reason for this is simple - taking apart an original system1 power supply is a lot of work.

The Gottlieb System 1 power supply board and metal "L" frame, modified
with a new C1 capacitor and an added ground wire to the cap's negative lead.
On these large replacement caps, I use heat shrink tubing over the new
C1 capacitor leads to prevent them from shorting out against the metal
"L" frame or other components.

    -12 Volts for the CPU board.
    The stock Gottlieb System 1 CPU board requires -12 volts DC for the six spider chips to work. If an otherwise working game is powered on with the -12 volts missing (due to a bad power supply or bad connectors), all the CPU controlled coils will lock-on (and most of the CPU driven lamps), and the game will not boot. Obviously this needs to be fixed before proceeding.

Notice the lower Power Supply A2-J1 female connector is labeled
"This Side UP". Don't mis-connect that (it's easy to do unfortunately).

Another Gottlieb System 1 power supply board mounted in its metal "L" frame.
This one has been modified with a 69 volt LED and a new 10,000 mfd filter cap.

    Transformers.
    There are two transformers in the bottom panel of a system1 game. The large transformer (C-17924) powers the coils, General Illumination, and CPU controlled lamp voltages. This transformer is very robust and seemingly never fails. The small transformer (B-17921) powers the logic voltages (ultimately 5/-12 volts), and all voltages for the score displays (69 volts AC and the reference voltages). Unfortunately this small transformer is fragile, especially the 69 volt score display windings. I have seen this transformer fail.

    The System 1 power supply has several main power blocks. Treat and test each block independently. There

    • Displays Main power:
      • +60 and +42 volt DC output.
      • 69 volts AC input.

      For the score displays (the smaller credit/ball display uses the lower +42 volts, and the larger 6 digit score displays use the +60 volts). Note the "reference" voltages for the displays (+4 and +8 volts DC) are *not* generated by this circuit (they are created by the +5/-12 volt logic circuit and these two reference voltages are required to make the score/credit displays work).

      When measuring the +42/60 volts with a DMM, be aware the ground for these two voltages are separate and distinct from the other grounds for all the other voltages. Therefore when testing the 60/42 volts I recommend using the negative lead of the large 200mfd 150 volt power supply C6 capacitor as the ground point. Yes all the grounds do tie together at the brass ground strip by the transformer (but all the connectors for the whole game must be attached and in good condition), so just use the power supply C6 cap's negative lead for the DMM's ground.

      The input AC voltage is rectified by diodes CR6-CR9 (1N4004) and filtered by capacitor C6 (200 mfd 150 volts). Transistor Q2 (TIP31c) regulates the output voltage with the help from Q4 (MPS-A43) and zener diode CR11 (1N4742 12 volts). Current limiting is done with Q3 (2N3416) and R13 (33 ohms). Output voltage is adjustable to 60V with a trimmer pot R16 (1k ohms). A 18 volt zener diode CR12 (1N4746) is used to drop the 60V to 42V for the smaller credit display. This is not a regulated voltage, as a zener diode is used to prevent too much voltage going through the circuit - if all the displays are disconnected the voltage will be higher than if all the displays are lit.

    • Logic/Display Reference Power
      • +5 and -12 volts DC output for CPU board.
      • +4 and +8 volts DC "reference" for score/credit displays.
      • Two times 11.5 volts AC input.

      The +5 volts DC adjustable by trim pot R4 (1k ohms.) The +5 volts is used for the CPU and driver board logic. The +4 and +8 volts are the offset voltages for the score displays. Interestingly the 4 and 8 volts DC actually goes back to two different center tap of the big transformer to raise the potential of the transformer above zero volts. The 4 volts goes to the center tap of the 3 volt AC line, and the 8 volts goes to the center tap of the 5 volt AC line. Weird stuff, but that's how the blue Futaba score displays work. Display filament bias voltage +8 volts DC is done with an 8.2 V zener CR21 (1N4738) and resistor R21 (100 ohm but 680 ohms pre-6/78, so use 100 ohms) from the same voltage used to generate +5 volts DC. Credit displays bias voltage +4 volts DC is made with two series diodes CR22/CR23 (1N4148) from the +5V output. 5 volts AC from the transformer is rectified by CR1/CR2 (1N5401 3amp 100v), and then filtered by capacitor C1 (which was 2900 or 4700 mfd, and should be replaced with a new 6800 mfd or higher cap). A 723 regulator and series pass transistor Q1 form a 5 volt regulator, whose output can be adjusted with trimmer R4 (1k ohms). Current limiting is done with resistor R1A (.18 ohm 2watt).

    • Coil Drive Reference Power
      • -12 volts DC output for CPU board.
      • Two times 14 volts AC input.

      Intermixed with the 5 volt circuit is the -12 volts DC. This is used for a reference voltage for the coil drive circuit on the CPU board, and the Rockwell PPS-4/2 spider chips that require -12 volts. Note if using a replacement CPU board like the NiWumpf this -12 volts is not needed!

      The negative voltage -12V is created by rectifying two times 14 volt AC transformer windings with diodes CR3 and CR4, and filtered by cap C4 (200 mfd 150 volts). Then a 7912 voltage regulator is used to keep the -12 volt DC output right at -12 volts.

    • Coil Power
      • 25 volts DC output for game coils.
      • 25 volts AC input.

      Coil power is unregulated. 25 volts AC power comes from the transformer located in the bottom panel of the game. It then goes through a 5 amp SB fuse and a bridge rectifier located next to the transformer, converting the voltage to 25 volts DC. The coil power then goes to the playfield.

    • CPU Controlled Lamp Power
      • 6 volts DC output for game lamps.
      • 8 volts AC input.

      CPU controlled lamp power is unregulated. 8 volts AC power comes from the transformer located in the bottom panel of the game. It then goes through a 5 amp slow-blow fuse and to a bridge rectifier located next to the transformer, converting the voltage to 6 volts DC. The lamp power then goes to the backbox and playfield. Note the drop from 8 volts AC to 6 volts DC. Since the power is unregulated, the drop is due to the lamp load. The more lamps, the greater the voltage drop.

    • General Illumination Lamp Power
      • 6.3 volts AC output for GI.

      The General Illumination (GI) is taken directly from the transformer through a 10 amp normal blow fuse, then directly to the backbox and playfield.

    Replace Power Supply Capacitor C1 Now!
    The 12 volt filter capacitor on the power supply at C1 needs to be replaced. There is no skipping this step. The original 2900 mfd 25 volt capacitor is way too small, and likely very worn out. Replace it with a new 6800 to 10,000 mfd 16 volt or higher capacitor.

    Score Display Flicker.
    If the score displays flicker, power supply cap C6 (200 mfd 150 volts) and C4 (1000mfd 35V) needs to be replaced.

Testing the System1 Power Train.

    Before powering the game up, it's good to know if the power supply (in its current state) works. Here is a good way to test a System1 power supply. This is a good generalized way to "bring her up", without smoke and fire.

      Power Supply Test, Step One:
      • Make sure game is off. Check all fuses in the bottom panel of the game by removing each fuse and testing with a DMM set to continuity. Make sure all fuses are the proper rating and type (NB normal blow versus SB slow blow)!
      • Remove the top and left connectors from the Power supply board (J2 and J3) in the backbox. Leave attached power supply connector J1 (the bottom connector). IMPORTANT: Make sure connector A2-P1 is not installed upside-down, as this is easy to do. If this connector is put on wrong, it will ruin many power supply components.
      • Note Gottlieb uses "J" as the male header pin designation, and "P" as the removable (female) connector designation. That is, P1 (female) attaches to J1 (male, detachable) on the power supply board. I say this to avoid confusion and that P1 mates to J1, so the voltages for say A2-P1 pin 1 is the same as A2-J1 pin 1 (remember that A2 is the board designation, in this case the power supply).
      • Power the game on.
      • Check the input voltages. This is at A2-P1/A2-J1 (bottom of power supply board). Note NO Key pin on this connector! Pin 1 (white/blue wire) is the left-most pin, below the two large diodes. Since there is no key on the J1/P1 connector, this means you can attach the plug upside down, which you obviously do not want to do. SO BE CAREFUL.

        A2-P1/J1 (bottom most power supply connector).
        This is the input AC voltages from the transformer.

        • A2-P1 pin 1 = 11.5 volts AC (wht/blue). LEFT MOST PIN.
        • A2-P1 pin 2 = 11.5 volts AC Return (wht/org)
        • A2-P1 pin 3 = common (ground, black)
        • A2-P1 pin 4 = 14 volts AC (wht/brn)
        • A2-P1 pin 5 = 14 volts AC (wht/purple)
        • A2-P1 pin 6 = 69 volts AC (blue/wht/red)
        • A2-P1 pin 7 = 69 volts AC Return (org/wht/red)

      • Check the output voltages. If the +5 or -12 volts is out of spec, there is a power supply problem. Do NOT attach power supply connectors J2 and J3 until you are sure all voltages are good (otherwise damage to the circuit boards can occur).

        A2-P2/J2 (top most power supply connector).
        This provides +5 and -12 volts DC to the CPU board. These are regulated voltages.

        • A2-P2 pins 1,2 = +5 volts DC (red).
          Note voltage is adjustable via the top left pot on power supply board, adjust to 5.10 volts.
        • A2-P3 pin 3 = Key
        • A2-P2 pins 4,5 = Ground (black)
        • A2-P2 pin 6 = -12 volts DC (blue).
          Should be -11.9 to -12.1 volts (yes this is a negative voltage).

        A2-P3/J3 (right edge of power supply board).
        This provides 60/42 and 8/6 volts DC to the score displays. These are all unregulated voltages.

        • A2-P3 pin 1 = 60 volts DC (wht/blue)
        • A2-P3 pin 2 = Key
        • A2-P3 pin 3 = 42 volts DC (wht/org)
        • A2-P3 pin 4 = not used
        • A2-P3 pin 5 = Ground (black)
        • A2-P3 pin 6 = not used
        • A2-P3 pin 7 = +4 volts DC (blue/wht/blk)
        • A2-P3 pin 8 = +8 volts DC (grn/wht/red)

      Note when testing all the score display voltages at A2-J3 you *must* use the ground J3 pin5 at the right side connector! (Yes, the ground for the power supply voltages is different than the logic ground.)

      Unregulated voltages (42/60 volts) can be higher than expected. For example, seeing 48 volts for the 42 volts test point, or 8.6 volts for the 8 volts test point are all Ok. Also 65 volts for the 60 volts is Ok, but there is a trim pot to adjust that voltage too. Regulated voltages like +5 volts should be in the 5.0 to 5.15 volt range (there is a trim pot to adjust the +5 volts). Also the -12 volts should be -11.9 to -12.1 volts.

      Power Supply Test, Step Two:
      If all voltages from 'step one' are present, continue with these steps.

      • Make sure game is off, and attach the connector from power supply A2-P2 (top most connector) to CPU board A1-J1 (left most connector). All other CPU board and driver board connectors can be disconnected.
      • Power the game on.
      • Check for +5 volts at capacitor C16. Capacitor C16 is the top electrolytic cap next to connector A1-J1. Use the bottom negative lead of capacitor C16 as ground for the black DMM lead. Use the top positive lead of cap C16 for the read DMM lead. This should show 5.0 to 5.1 volts DC.
      • Check for -12 volts at capacitor C17. Capacitor C17 is the bottom electrolytic cap next to connector A1-J1. Use the bottom negative lead of capacitor C17 as ground. Put the positive red DMM lead on the top lead of cap C17. This should show -11.9 to -12.1 volts DC.

      These steps make sure that the +5 volts and -12 volts are not dragged down by the CPU board, or the connector going from the power supply to the CPU board. If +5 or -12 volts goes down, try adjusting the power supply trim pot. If voltage is below 4.8 volts, this will need to be fixed.

      Power Supply Test, Step Three:
      Continue with these steps.

      • Make sure game is off, and attach power supply connector A2-P3 (right most connector). This is the score display power connector.
      • Optional: Attach the CPU board connectors A1-J2 and A1-J3. These are the right most CPU board connectors going to the displays.
      • Optional: Attach CPU board connector A1-J6 (bottom edge of CPU board, second connector from the left). This is the slam switch and test switch connector. Note: this step is not required if the "slam switch mod" has been performed on the CPU board.
      • Power the game on.
      • Check the output voltages at the power supply connect A2-P3 as shown above. Hopefully the voltages have not changed more than 5% to 15%. If they have, there may be a shorted score display. Turn the game off and remove all display connectors. Power the game back on and check the voltages. Then turn the game off again and re-connect the score display connectors one at a time and check the voltage. This way the problem score display can be easily identified. Note the bottom panel power fuse for the score display.

      If 60 volts and/or 42 volts are now missing, first check the four 1N4004 diodes (CR3,CR4,CR6,CR8) on the power supply board. (Also check CR7 and CR9 too.) With the power off, use a DMM set to diode function - they should read .4 to .6 volts in one direction (black DMM lead on the diode banded leg), and null voltage in the other. There could also be a shorted score display! Hopefully this is not the case, as a shorted display can easily take out the 7448 chips on the CPU board. Replace the 60 volt fuse in the bottom panel (it may or may not have blown!), and disconnect all but ONE of the score display connectors. Power the game on and check for 42 and 60 volts. Repeat this, adding one score display connector at a time, until the offending score display is found. Warning: only attach connectors with the power OFF.

      Low 60 Volts on the Power Supply.
      An often seen problem with the 60 volt supply (which also gets turned into 42 volts) is low voltage. As in the voltage measures around 20 volts, and transistor Q2 gets *really* hot. After checking the values of the resistors, testing Q2 (TIP31c), and testing the zenor diodes in the H.V. (high voltage) section, no problems are found. The likely cause of this low voltage are bad capacitors C7 (disc .1mfd 200v) and/or capacitor C9/C10 (10mfd 160 volts.)

    +5 Volt Transistor and Heat Related Problems.
    The +5 volt transistor Q1 (PMD12K40 or 2N6059) makes the whole power supply board get quite warm. This eventually causes the filter capacitors to dry out. A dried out C1 capacitor in +5/-12 volt circuit can cause strange problems and game lockups. Improper filtering of 60 volt display voltage by cap C6 (200 mfd 150 volts) can cause the score displays to flicker or go dim.

    In addition, the Q1 transistor can get so hot that it creates cold solder joints on other power supply components. Sometimes even the 5 volt transistor Q1 can fail. The original PMD12K40 transistor is hard to find, but a common replacement is the 2N6057 or 2N6059. This is a 60 volt, 8 amp NPN darlington. After years, the trimmer potentiometers also begins to fail because of dust, causing overvoltage protection to trip or other problems. The trimmers should be replaced with new ones. Rectifier diodes CR1 and CR2 are underrated too, and it's good to replace those with at least 4A diodes. Note the IC1 power supply part is a UA723CL, which is round metal cased version of the LM723 DIP package.

    Power Supply Connector A2-P1.
    Connector A2-P1 is removed when the backbox is taken off. When replacing A2-P1, it is very possible for the connector to attach upside down. There is a 'this side up' sticker, but it may have been lost over time. Pay particular attention to this as an upside down J1 connector will ruin power supply components.

    +5 Volt Power Supply tips and fixes.

    • Make sure that Q1 (large metal transistor mounted on the back of the heat sink) is electrically isolated from the metal back plate (there is a thin mica insulator for this purpose.)
    • If +5 volts measures 2.4 volts, then Q1 (PMD12K40 or 2N6059) is bad.
    • If no +5 volts, check pin 7 of IC1 (UA723CL). This should be 14 to 15 volts (with Q1 removed). In this voltage is not 14 to 15 volts, IC1 is bad.
    • If Q1 gets hot and there is no +5 volts, then SCR101 (S107Y1) is bad.

    Remember all Power Supply Transistors are Isolated from the Metal Frame.
    Like the large +5 volt Q1 regulator, the smaller transistors Q2 Q3 (7912 for -12 volts) and (TIP31c for H.V.) which hang off the top and bottom edges of the power supply board (respectively) also need to be electrically insulated from the metal back plate. This is done using small plastic insulators, which the mounting screw for these transistors penetrate. Often these insulators go missing. Additionally there is a mica (clear) insulator that mounted between the transistor and the metal frame. If the plastic insulator and the mica insulator are not installed, diodes CR3 and CR4 (1n4004) will absolutely burn and the H.V. fuse will blow. So what do you do? For the plastic insulator you can make your own using 3/32" heat shrink tubing and some plumbing washers (see picture below.) For missing mica, that can be purchased from any decent electronics store.

Making your own isolating bolt system for power supply transistors Q2 and Q3.
The metal heat sinks cannot electrically touch the metal frame of the power supply,
which they are bolted. This is done using a mica insulator and a plastic bolt insulator.
It's easy for the bolt insulator to go missing, so you can make your own with 3/32"
heat shrink tubing and a plumbing washer.

    CPU Board Over-voltages.
    Both +5V and -12V outputs are equipped with a protection circuit made of thyristors SCR101/SCR201 (S107Y1) and zeners diodes CR101/CR201 (1N4734/1N4743). If the output voltage rises over zener voltages (5.6 and 13 volts), the thyristor energizes and shorts the output, causing the fuse to blow.

    Testing a Bridge Rectifier.
    There are TWO bridge rectifiers used in System1 games, both located on the game's bottom panel. The bridge located closest to the ground plane is for the CPU driven lamps, and converts 6 volts AC to DC. If none of the CPU controlled lamps work, check this bridge first. The other bridge rectifier is for the solenoids. We covered how to test a bridge rectifier above in the Blown Fuses section.

    Replacing a Bridge Rectifier.
    Gottlieb specified their bridge rectifiers as a VARO VK438 or VL038. These are obsolete types of bridges. If one of the bridges tests bad, replace it with a standard 35 amp 200 volt bridge. (MB3502 or MB3504 bridge with lug leads). The "MB" specifies the type of case the bridge is in. The "35" is number of amps. The "02" means 200 volts, or "04" means 400 volts. Higher values can be used in either amps or volts. But don't go lower on either value.


2c. Mod: Protecting the Small Transformer

    The Small Transformer Problem.
    Over the years we've noticed people asking for the small transformer on Gottlieb System1 games. Remember there are two transformers on the bottom board of any System1 game - a larger transformer, and the small transformer. The small transformer is the problematic one, hence requests for people looking for this transformer. It provides:
    • input 11.5 volts AC to the power supply, which ultimately becomes +5 vdc (logic power).
    • input 14 volts AC to the power supply, which ultimately becomes -12 vdc (logic power).
    • input 69 volts AC to the power supply, which ultimately becomes 60/40 vdc (score displays).
    • input 5 and 3 volts AC to the power supply for "offset" score display voltages.

    So as you can see, this smaller transformer is pretty darn important. The larger transformer, which supplies 25 volts (for the coils) and 8 and 6 volts (for the lights) could be substituted with heck even an old EM transformer in a pinch. But the smaller transformer which provides all the logic/score display power, that is unique.

Bottom board on a Gottlieb Joker Poker, showing the two transformers. Note on this game fuses have been added to the smaller transformer.

    The problem has to do with the power supply board in the backbox. If you look at the schematics, the two input voltages 14 and 11.5 volts AC go directly to the power supply board. That is, there's no fuse between the rectifying diodes on the power supply, and the transformer. This is unlike the 69 volt AC input going to the power supply for the score displays (a 1/4 amp fuse is used here.)

    The reason for a fuse is simple - often the power supply board rectifying diodes short. When this happens, it's basically taking the two AC lines from the transformer, and tying them directly together. If there's no fuse there, the windings in the transformer because the weakest link in the chain, and hence the transformer becomes the fuse! Obviously this is not good, and the transformer dies. (There's no way to fix this either, other than a replacement transformer.)

Bottom boards schematic from Joker Poker. Notice the B-17921 tramsformer only has a fuse for the 69 volts shown by the blue circle (nothing for 11.5 and 14 volts.) Blue arrows show where there should be fuses for the 11.5 and 14 vac lines.

    Looking at the power supply schematic shows no fuses for the 11.5 and 14 volt AC inputs either. Why did Gottlieb forget to do this? Hard to say, but the outcome is if CR1/CR2 diodes short (11.5 vac rectifiers, which ultimately make the +5 vdc logic power), or the CR3/CR4 diodes short (14 vac rectifiers, which ultimately make the -12 vdc logic power), the transformer become the "fuse". Yikes!

Gottlieb power supply schematic, no fuses here either.

    Note Gottlieb didn't even have an input 120 volt side fuse for this small transformer either! Well not intially at least. Somewhere around Pinball Pool/Solar Ride they added a 1amp input 120volt power fuse for the small transformer. This helped the problem, and was a good idea, but really wasn't the solution. All this fuse does is prevent the transformer from starting on fire if it shorted!

    So the answer is to add two fuses (and a third fuse if no small transformer input fuse). This should prevent any transformer problems if the power supply rectifying diodes short.

    Adding the Fuses.
    On the output side of the transformer, there are many different "taps" (solder lugs). The lugs we are interested in are number 6 (14 vac) and number 7 (11.5 vac) taps. Essentially what one needs is this:

    1. Mount two fuse holders next to the small transformer.
    2. Remove the wire from lug #6 (either yellow/blk/blk or white/blue), and solder it to one lug of the fuse clip.
    3. Solder a wire from the other lug of the fuse clip in prior step back to the transformer lug #6 (where the yellow/blk/blk or white/blue wire was attached.)
    4. Install a 2 amp slow blow fuse. This is the AC power that ultimately becomes +5 volts.
    5. Remove the wire from lug #7 (either yellow/red/red or white/brown), and solder it to one lug of the fuse clip.
    6. Solder a wire from the other lug of the fuse clip in prior step back to the transformer lug #7 (where the yellow/red/red or white/brown wire was attached.)
    7. Install a 3/4 amp fast blow fuse. This is the AC power that ultimately becomes -12 volts.
    8. If there is no input fuse for the 120 volts going to the small transformer then...
    9. Mount another fuse clip next to the transformer.
    10. On the side of the transformer closes to the side of the cabinet wall, remove the brown wire from the transformer.
    11. Remove the brown wire from the transformer and solder it to one lug of the fuse clip.
    12. Solder a wire from the other lug of the fuse clip in prior step back to the transformer lug (where the brown wire was attached.)
    13. Install a 1 amp slow blow fuse for the transformer's 120 volt input power.

The small transformer with two new fuses added for 11.5 and 14 vac power lines. On the input side of the transformer, a third fuse was factory added (not shown) for the input 120 volts.

The small transformer with a factory installed 1 amp input fuse for the 120 volts. If your games doesn't have this, you should add it (as documented above.) Note this game does not (yet!) have the two output 11.5/14 vac fuses added.


2d. Battery Replacement/Corrosion (CPU board Reset/Clock Circuits)

    The Gottlieb DataSentry battery mounted on an original System1 CPU board.
    This battery apparently has not leaked (this board was lucky).

    This fix is mandatory. All Gottlieb System1 boards use a recharagable "DataSentry" or AA nicad 3.6 volt battery. When these batteries don't get used regularly, they can leak the alkaline potassium hydroxide and volatile gases that destroy the CPU board components and connectors. Removal of a 30+ year old rechargable battery is mandatory!

    Can I run with No battery?
    Yes you can, but it's not suggested. System1 games with no battery will show some pretty wacky high scores and credit numbers. It's often confusing, making you think there's a problem when there isn't one. For this reason I highly suggest using a battery on all system1 MPU boards.

    New Battery
    To replace the original battery, add a remote three "AA" battery pack and a 1N4004 or 1N5817 diode (banded diode end first connected to the pcb "+" pin, and the non-banded end connected to the positive lead of the battery pack). The diode is used so the recharging circuit doesn't try to charge the AA batteries. Also the game can work with no battery, but it can also exhibit some strange behavior without the battery. So my advice is to have a remote battery holder with AA batteries and a charging block diode.

A remote battery pack with a blocking diode. The red battery pack wire
goes to the "+" pad on the CPU board.

A remote battery pack mounted in a Gottlieb Countdown. The red battery pack wire
goes to the "+" pad on the CPU board.

    Coin Battery Installation.
    A very clean alternative to a remote AA battery pack is to use a CR2032 coin style battery. These are readily available at drug stores, as they are a common coin battery (used in most computers for BIOS settings.) A coin battery holder is required for installation, as is a blocking 1n4001 or 1n4004 diode (you don't want the game to charge this battery!) Below is a picture of an installed coin battery and holder, with a 1n4001 diode installed on the back of the board. A single 1/16" hole was drilled in the board to accomodate the coin battery holder, and that feeds the positive lead of the battery holder to the back of the board. Then a 1n4001 block diode is installed on the back side for a nice clean look.

CR2032 coin style battery and holder installed with a block diode.

    Memory Back-Up Capacitors.
    A decent alternative to batteries is to install a memory back-up capacitor. These capacitors will charge when the game is on, and slowly discharge to keep the memory alive when the game is off. The advantage to these capacitors is they never wear out, and they won't leak corrosive materials. The down side is the game must be on for about one hour every month to maintain their charge (but the amount of charging time and how long the back-up cap will keep memory is variable from CPU board to CPU board). Also, the game must be on for about 8 hours continuously to initially charge the capacitor. Frankly I'm not a real big fan of memory caps, as I much prefer a remote mounted AA battery pack (mostly because sometimes my games aren't turned on for months at a time, and the battery pack will keep the memory alive for much longer than a back-up cap.)

    Back-up capacitors are about the size of a stack of nickels, and Jameco (800-831-4242) sells 1 Farad memory caps, part# 142957. Remember CPU board memory "save" duration has to do with the exact memory brand on the CPU board, its age, and its exact manufacturing specs. Some memory chips have different power consumption rates, hence varying results can be seen with memory backup caps. Some CPU boards will maintain their memory for months with a backup cap, and others may only last a week. "Your mileage may vary" is probably a good statement about memory backup capacitors.

    When installing back-up capacitors, the minus and positive leads are often not labeled on the cap. There was only a black line on the cap to designate the negative lead (the CPU board is labeled; the positive hole has a "+" next to it).

    If the installed memory cap doesn't seem to work (and it was installed correctly), check the isolation diode CR26 (1N4148) using the diode function of a DMM. Its job is to make sure the cap/battery doesn't try and power the entire CPU board when the game is off (this would drain the cap/battery quickly).

    Check for Battery Power at the 5101 RAM chip.
    No matter what style back-up battery you use, make sure the battery voltage is getting to the 5101 RAM chip. The 5101 is three chips to the right of the Game PROM, along the top left side of the CPU board. Put the red lead of your DMM on the upper right pin 22 of the 5101 RAM, and the black lead on ground. You should get 3 to 4.5 volts DC if the battery backup is doing its job.

    Be Sure to Zero Out the Game's Audit Memory.
    After the new battery or memory cap is installed and working, I would highly recommend zeroing out the game's audit memory. If you don't do this and the battery was removed or dead, the CPU memory could have some wacky data which may cause some strange game issues or weird high score.

    To zero out the audit memory, turn the game on, and press the white diagnostic button inside the coin door. This will show "0" in the credit display, and the audit information in all the score displays. To zero out this memory position, press the push button mounted on the CPU board, and the score displays should all go to "000000". Press the coin door diagnostic button once to advance to the next audit number, and again zero this out using the CPU board push button. Repeat this for audits 0 to 10. Press the coin door diagnostic button again, and then exit the audits by either powering the game off, or by opening the slam switch (or closing a tilt switch). This process will clear the game's audit memory.

Removing the Old Battery and Fixing Corrosion.
    The absolute best way to remove old battery corrosion is to use a bead blaster. This allows the cleaning of the circuit traces easily, and often without removing all the lightly effected components. There's no substitute for bead blasting, it works the best. Note after bead blasting and replacing any damaged components, spray the effected area with a light coat of Krylon Crystal Clear. This will prevent the traces from oxidizing in the future, and keep the repair looking nice.

The back side of the MPU board, showing the connector traces right
below the battery. This is what battery corrosion can do. This is so bad
the board may not be usable. Bead blasting or sanding the corrosion will
probably take off most of the copper, leaving nothing for the connector
housing's pins to "bite".

    If you don't have access to a bead blaster, you can remove corrosion the old fashioned way. Here are those battery corrosion repair steps:
    1. Remove the CPU board from the head box.
    2. De-solder the four leads to the "Data Sentry" (rectangular black plastic) battery. Remove the battery and discard.
    3. If any components are damaged by the battery (look for green and/or gray!), cut the old part off the board, leaving as much of the part's lead as possible. Heat the solder pad on the circuit board with a soldering iron, and pull the cut off lead out of the board. If the lead is not coming out easily, add some new solder to the solder pad. This will help distribute the heat. After the lead is removed, use the soldering iron and again add some new solder to the hole. Then use a solder sucker (Soldapulit) and de-solder the hole.
    4. If there is any gray or greening of a part's leads, replace it. If in doubt, replace it.
    5. Check the edge connector fingers (pins) for "green". If the metal pins are green, they will need to be replaced!
    6. After removing the damaged components, sand all green/gray areas of the board with 220 grit sandpaper, including edge connector fingers. Sand until the copper is bright, which will allow solder to stick.
    7. Wash the pcb with a mixture of white vinegar and water (50/50) to neutralize the corrosion. Scrub with a toothbrush. This is very important! If this step is skipped, the corrosion will return.
    8. Rinse the washed board with clean water.
    9. Rinse the board with 99% pure alcohol. This will dissolve and wash away the water. Repeat this step. The alcohol will evaporate quickly.
    10. If sanding the edge connector fingers, heat them with your soldering iron and tin them with solder. Wipe with a cloth while still hot to smooth and remove the excess solder. This can also be done to any traces sanded on the board, but the edge connectors fingers most often need this. Corrosion opens the pores of the fingers, and the new solder can fill these and provide much better connectivity to the connector pins.
    11. Check the edge connectors for broken traces leading to the fingers. This is pretty common on system1 CPU boards where the trace breaks where it meets the wider edge connector finger.
    12. Replace all removed components (except the battery!) Any removed chips should be replaced with a good quality socket.
    13. Check the connectors themselves! If the board has corrosion, the connectors will have corrosion too! Replace the connector pins if any damage is seen (see the connector section below). Pin replacement is the ideal solution.

A bead blaster. This is an inexpensive ($100) blaster available from Harbor
Freight or equivalent store. It connects to an air compressor.

A view of the inside of the bead blaster.


2e. Ground Problem Fixes (CPU, Driver board, Power Supply, Sound board)
    These fixes are mandatory.

    The Gottlieb Grounding Problem.
    There are multiple problems with ground in System1 games. One problem relates to differences in ground between the CPU board and the Driver board. The other problem relates to differences in ground between the circuit boards and cabinet ground. We address and fix both problems below.

    First there is the problem with ground between *cabinet* ground, and circuit board ground. John Robertson documented this problem back in 1987. There is a single ground connection between the cabinet ground and circuit board ground on the power supply. If this single connection has resistance (which is common on older games), problems occur. This resistance, with the current drawn by the Driver board through the power supply, causes a voltage shift in the power supply's ground line. If the voltage shift gets up to .5 volts relative to the cabinet ground, the solenoid driver transistors are no longer biased off, and start to conduct. This can cause playfield coils to "lock on" and burn, damaging the coil and its associated driver transistor. This single problem made many people think Gottlieb games were "unreliable".

    Mandatory Ground Modifications Steps.

    1. Test all the driver board transistors. This only takes a few minutes since the Driver board is already removed. If any test bad, replace them now to prevent future problems. See the Testing Transistor with the Driver board Removed section for info on how to do this. Do NOT skip this step! If the driver board is out of the game, it only takes a moment to test all the transistors.

Step 1: An added (red) ground wire from the Power Supply's negative lead of
capacitor C1 to the backbox ground plane.

    1. On the power supply board, solder an 8" piece of wire to the negative lead of capacitor C1 (the main +12/+5 volt filter capacitor). The negative lead is the right side cap lead. There is no need to disassemble the power supply to do this. Note if the original C1 filter cap is still present in the power supply, now is a good time to replace it. Use a new 6800 mfd to 10,000 mfd 20 volts or higher electrolytic capacitor. Again no need to disassemble the power supply to do this; just cut the current cap's leads as close to the old cap as possible, and tie/solder the new cap leads to the old cut cap leads.

      Attach the other end of the wire to a screw holding the metal backbox plane. If using a Rottendog replacement System 1 power supply, skip this step as the Rottendog power supply already has it's ground connected to the metal tabs bolting the power supply to the metal "L" frame.

Step 2: An added (red) ground wire from the CPU board's negative lead of capacitor C16
(lower lead of the left upper electrolytic) to the backbox ground plane.

    1. On the Gottlieb System1 CPU board, solder an 8" wire to negative lead of capacitor C16 (the bottom lead of the left side upper blue electrolytic capacitor). Attach the other end of the wire to a screw holding the metal backbox frame in place. If using a Niwumpf board, scrape the green solder mask from the large ground trace just below the blue electrolytic capacitor C0 negative lead, and solder an 8" wire to that trace. (Yes you should still do the ground mod is using a Niwumpf board - the grounding problem is part of the wiring design, and replacing the CPU board does not make the ground problem go away.) Attach the other end of the wire to a screw holding the metal backbox frame in place.

Step 2b: An added (red) ground wire from a Niwumpf board's negative lead of
capacitor C0 to the backbox ground plane.

    1. On the driver board, solder an 8" piece of wire to negative lead (bottom lead) of capacitor C1 on the right side of the driver board. Attach the other end of the wire to a screw holding the metal ground plane to the backbox.

Step 3: An added (red) ground wire from the driver board's negative lead of
capacitor C1 to the backbox ground plane.

    1. If the system1 game has a sound board, this needs a common ground too, especially if it is the "newer" system1 sound board. On the newer sound board, it creates its own 5 volts from a on-board 7805 voltage regulator (it does not get 5 volts from the power supply). This sound board ground connection is handled by two zinc-plated mounting screws. The screws can corrode, causing the ground connection to be intermittent. This can even cause the sound board regulator output voltage to rise way beyond 12 volts, killing chips on the sound board (in particular the hard to find and custom to this sound board 6530 RIOT chip). To fix this make sure the two ground screws are NEW and free of corrosion.

    At this point, the mandatory grounding modifications are done.

Suggested Driver Board Ground Mods.
    Though the following System1 driver board grounds are not manditory, I highly recommend them. Remember Gottlieb/Rockwell did not centralize their grounds (like say Bally or Williams). Meaning along the bottom edge of the driver board, there are SEVEN separate ground wires to the connectors A3J2 to A3J5. These seven separate green grounds all end up at the central brass ground plate on the bottom board of the game. But if one of the ground connector pins on A3J2 to A3J5 fails, then part of the driver board looses its ground. This can cause a variety of problems, mostly a group of coils or lights to not function.

    To fix this problem, it's a good idea to tie all the driver board grounds together. Now if one of the ground connectors pins fails on connectors A3J2 to A3J5, it's not a big deal, as there's six other ground pins to take up the slack. Additionally having all the driver board grounds tied together means there's far less chance of a "floating ground" (as described above.) For this reason, these optional ground modifications to the driver board are recommended.

Driver board with optional ground modifications.

    Notice in the picture above the blue arrows showing the green wires added. There are thick traces along the front component side of the board, bring ground to the MPS and other transistors. These all should be tied together.

    In the original "mandatory" ground mod, only the logic ground is physically tied to the centralized metal ground plane. In this optional ground mod, all the grounds are tied together (including the solenoid and lamp grounds.) This provides a more consistent and redundant ground for all devices.

    The first step is to modify the original "mandatory" ground mod. We originally added a ground wire to the negative side of the C1 driver board capacitor. But the thick trace directly below that ground point is also a ground. So with a quick scrape of the green mask from the trace, the added jumper wire can bridge both traces, tying these grounds together. (Blue circle below.)

    In addition, also shown with three blue arrows below, the large (thick) ground traces that travel beneath the MPS transistors should also be tied together, and then tied to the large trace at the right.

Driver board with optional ground modifications.

    In the picture below, the left side of the driver board is shown. (The right most green arrow is also shown on the above picture.) Here two more grounds, again traveling below the MPS transistors, are tied together. There is also a vertical wire added to tie the ground for the larger TIP transistor to the ground along the bottom of the MPS transistors.

Driver board with optional ground modifications.

    There is one modification on the back side of the driver board too. Two ground traces near the J4 connector and beneath the large 2n3055 transistor travel very close together, but do not touch. Using a razor blade remove the green solder mask, and drop a blob of solder across these two traces. (See the picture below with the blue circle.)

Driver board with optional ground modifications.

    That completes the optional System1 driver board modifications. Again I highly recommend this approach, as redundant grounds is a good thing for Gottlieb pinballs.


2f. Connector Problems (Connections & Re-pinning) - Mandatory

    Connector Warning - Power Supply A2J1 Connector.
    Before we talk about connector pin problems, I should mention a potential pitfall with all system1 games. When a system1 game is taken apart, the connectors have to be removed from the boards in the backbox, so the head can be taken off the game. The problem is upon reassembly, one connector can be put on in reverse. Or it can be installed one pin off to the right or left. Talk about a catastrophic failure, this would put the wrong AC voltages from the bottom board into the power supply.

Power supply connector J1, which can be installed "upside down."
Obviously you don't want to install this connector wrong!

    A simple solution to this would have been using a different pinout for the A2J1 connector. But for some reason Gottlieb (Rockwell?) didn't do that. Instead they just put a sticker on the connector labeled, "this side UP." OK fine, but they are depending on a lot of confidence that either this sticker will stay on the connector, and that someone will actually read the message.

    After Joker Poker, Gottlieb did get the message and changed the female .156" Molex connector housing from 7 pins to 9 pins, and added pin blockers inside the housing at pins 1 and 9. This prevented the A2J1 female connector from being installed one pin to the right or left of the matching male pins. Unfortunately it did not solve the problem where the connector could be installed upside down.

    Just a warning to be careful with this plug. Install A2J1 correctly, with the green ground wire towards the left. Otherwise bad things wil happen.

    Connectors, Battery Corrosion, Vibration & Corrosion.
    Gottlieb System1 pinball games basically use one style of connector between the CPU, Driver and Power supply boards. They are single sided, crimped, .156" Molex card edge connectors.

    No System1 game should have "IDC" (Insulation Displacement) connectors (IDC connectors were introduced with Gottlieb System80 games.) If a system1 game does have IDC connectors, someone probably transplanted them to the game you're working with.

    These card edge connectors are rated for 25 "cycles" - that is 25 removal-installs. Over the life of a 20+ year old System1 game, certainly this life span has been exceeded. Combine that with battery corrosion problems and vibration from game play, and it's obvious that any Gottlieb System1 game will REQUIRE all the main connectors to be re-pinned. If you want your System1 game to work reliably, YOU MUST RE-PIN ALL THE CARD EDGE CONNECTORS.

    If there are battery corrosion problems, these card edge connectors just magnify the problem (and sometimes allow the leaking battery electrolyte to travel thru the connectors to other boards!) If there is any battery corrosion on the circuit board card-edge fingers, this MUST be removed before any other connector work is done. If corrosion is visible on the board, clean the edge fingers by lightly sanding the corrosion with 220 grit sandpaper to remove it, revealing the copper plating. After the corrosion is removed, wash the circuit board in a 50/50 mix of white vinegar and water. Use an old toothbrush to wash the board with the vinegar mix. Then rinse the board with clean water. Finally rinse the board with alcohol, and allow it to air dry.

    If the board's connector fingers were sanded, use a soldering iron and some rosin flux to re-tint the connector fingers with solder. Heat the finger, apply some new solder, then quickly wipe the solder off the finger with a rag. This should leave a "tint" of solder on the copper finger.

This System1 connector housing shows some terminal pins with gray/green corrosion
(especially 4th pin from left). This connector will need to be re-pinned.

    Connector/Board Numbering.
    Connectors are numbered in this fashion: the first "A" letter/number combination denotes which board the connector belongs. That is, A1 is the CPU board, A3 is the driver board, etc. After the board designation, the "J" letter/number combination is the actual connector number for that board. So "A1-J3" is board A1's (CPU board) J3 connector (note some Gottlieb documentation does not put a "dash" between the board and connector numbers). Below are a list of "A" numbers (applies to most System1 games):
    • A1 = CPU Control board.
    • A2 = Power supply board.
    • A3 = Driver board.
    • A4 = Score display boards.
    • A5 = Status digit display board (4 digits).
    • A6 = Sound board (where used).

    Here's a summary of the CPU board connectors. The connectors with a "*" next to it are the ones most often damaged by battery corrosion or vibration and need to be replaced most often.

    • A1-J1* (left): +5 volts, -12 volts, ground. CPU board power, 5 pins.
    • A1-J2 (top right): score display segment control.
    • A1-J3 (lower right): score display digits strobes.
    • A1-J4 (bottom right): not used on any system1 game.
    • A1-J5* (bottom center): data/address bus, +5 volt/ground to driver board.
    • A1-J6* (bottom left): switch matrix lines for coin door and slam switch.
    • A1-J7* (bottom far left): switch matrix lines for playfield.

    Commonly corroded connectors.
    The connectors that are most often rotted from battery corrosion are shown below. Note there is some variance from game to game, so check your manual. But these should help in a pinch while you're re-doing connectors.

A1-J6
Pin#
Color Function
1BlkGround
2Blue/BlkAnti Cheat Slam switch
3YellowSwitch Matrix Return 0
4OrangeSwitch Matrix Strobe 1
5BrownSwitch Matrix Strobe 2
6GreenSwitch Matrix Strobe 3
7PurpleSwitch Matrix Strobe 4
8BlueSwitch Matrix Strobe 0
9NoneNo connect

A1-J7
Pin#
Color Function
1Wht/Grn/BlkOuthole switch
2BlueSwitch Matrix Strobe 0
3OrgSwitch Matrix Strobe 1
4BrownSwitch Matrix Strobe s
5NoneNo connect
6PurpleSwitch Matrix Strobe 4
7GreenSwitch Matrix Strobe 3
8BlkGround
9NoneNo connect
10Yel/BlkSwitch Matrix Return 7
11Yel/WhtSwitch Matrix Return 6
12YelSwitch Matrix Return 0
13Blue/WhtSwitch Matrix Return 1
14Org/WhtSwitch Matrix Return 2
15Purp/WhtSwitch Matrix Return 5
16Grn/WhtSwitch Matrix Return 4
17Brn/WhtSwitch Matrix Return 3

The CPU to Driver board crimped connector.

    Replacing the Connector Pins.
    At this point it is time to replace the terminal pins inside the plastic card edge housings. Since all Gottlieb System1 games originally used crimped-on terminal pins, this job is fairly easy! For example, I can re-pin all the main Gottlieb System1 connectors in about an hour. The original plastic connector housings DO NOT need to be replaced, and can be reused!

    Parts and Tools needed:

    • Molex card edge pin extraction tool, part# 11-03-0003 or 11-03-0016.
    • Hand Crimping Tool: Molex WHT-1921 (part# 11-01-0015), Molex part# 63811-1000, Amp 725, or Radio Shack #64-410.
    • Molex .156" single side connector pins for 18-20 gauge wire, part# 08-52-0072. Get 200 of these.
    • Molex .156" Trifurcon connector pins part# 08-52-0113. Only need a handful of these for the two power supply connectors.

    Connector (terminal) pins will be required. Molex connector pins are somewhat difficult to order, as there are so many different varieties. Note the "chain" variety are not wanted. The chained variety are designed for high-speed installation machines, not single use. Purchase only phosphor-bronze tin plated pins (do not use gold pins).

A Molex terminal pin removal tool, part# 11-03-0016. This inexpensive tool is required.

    The Connector between the CPU and Driver board.
    This single sided connector harness often has corroded pins because the CPU side of the connector is near the battery. If the harness is missing, a new replacement can be purchased from Docent Electronics (937-253-2768).

Docent Electronics power supply to CPU board harness.

Crimp-On Connector Pin Replacement Instructions.

    If one connector pin is compromised, replace ALL the terminal pins in that connector. More information on crimping connectors can be found at pinrepair.com/connect.

  1. Insert the Molex pin removal tool into the slot between the terminal pin and the plastic connector housing (see picture below). The Molex tool will require a good stern push into the connector housing. Now gently pull the wire attaching to the terminal pin, and the pin should come right out of the connector housing.

Molex terminal pin removal tool, releasing a pin.

A terminal pin after removal, and two new .156" terminal pins.

  1. Cut the old terminal pin from the wire. Then strip the insulation from the wire back 1/8". Insert the stripped portion of the wire into the new terminal pin. Note the terminal pin has *two* sections which will be crimped onto the wire. The section closest to the contact point should grip the bare wire. The section furthest from the contact point should grip the wire's insulation.

Inserting the stripped wire into the new terminal pin.

  1. The wire is crimped to the terminal pin in two parts. First crimp the forward most part of the terminal pin to the wire (as shown in the picture below). Then crimp the insulation portion of the wire to the terminal pin. A Molex crimping tool Waldham #WT-1919 is shown below.

Crimping the wire to the new terminal pin.

  1. Repeat this procedure for each terminal pin in the connector housing. Replace each pin one at a time. This should prevent you from mixing up connector pins and where then go in the connector housing.

    Replacement Harness PS to MPU and MPU to Driver board.
    Steve Kulpa stevekulpa@yahoo.com and Docent Electronics docentelectronics.com sells brand new connector harness for the (often missing or damaged) power supply to MPU board connector, and MPU to driver board connector. Contact them for details, but the cost is excellent. They use tin plated crimped pins, trifurcon for the header connector on the power supply, and 22 awg wire for signals and 18 awg wire for power lines.

Steve's new Gottlieb System1 MPU to Driver board harness.

Docent's new Gottlieb System1 MPU to Driver board harness.

    When getting a new harness, I really recommend the new Steve Kulpa harness with the added diodes. Steve addes diodes to his version of this harness, because on early system1 driver boards, diodes are missing to protect the CPU board from coil voltage disasters. This is a very good idea, and this harness can be used on system1 games with or without protection diodes. This harness is for sale at Big Daddy Enterprises, and it's well worth the expense. Note using this harness with a Gottlieb driver board that has the diodes is fine too. (So always buy this version of the harness!)

Steve Kulpa's CPU to Driver board harness with diodes installed.

    Modifying your Current Harness for Diodes.
    On early system1 games (Joker Poker, Cleopatra, Sinbad) with first generation driver boards (no CR1-CR7 diodes installed), it's a good idea to modifying your current CPU to Driver board harness to add diodes. This will protect your expensive CPU board from coil voltage damage (if something goes wrong.) This modifiction saves you from having to modify the driver board adding diodes, if it's missing the CR1-CR7 diodes. (Note this modified harness can be used with later Driver boards too.)

Modifying an original CPU to Driver board harness with 1n4004 diodes.

    The point here is to add the CR1 to CR7 diodes, which are missing on early driver boards, to the harness. This protects the CPU board without having to do major modifications to the Driver board. If you're already working on this harness, this is a good modification.

Finished modified original CPU to Driver board harness with 1n4004 diodes installed.

    CPU to Driver Board Connector Pin Outs.
    Here's the connector layout for the harness that goes between the CPU and driver boards. It's handy info to have if you have to do some re-pinning. Remember all Sys1 games have the same set of solenoids/lamp wires, so this connector is identical for all sys1 games. For the coils this includes the outhole, the 3 chimes (or sound inputs), and the knocker, and the three additional solenoids (which may vary from game to game as coils 6, 7, 8.) But again the harness wiring is the same. Additional coils like the Kings drop target on Joker Poker is driven by a lamp driver and an under playfield mounted transistor. Yet again the lamp designations on this connector are the same for all sys1 games.

MPU
A1-J5
Pin#
Driver
A3-J1
Pin#
Color Function
111Blue/BlkSolenoid 7
212Org/BlkSolenoid 8
34Wht/GrnLD4 - Lamp Data 4
42Wht/BrnLD3 - Lamp Data 3
51Wht/OrgLD2 - Lamp Data 2
63Wht/BlueLD1 - Lamp Data 1
719Grn/Red100s Chime coil
818Purp/Red1000s Chime coil
99Yel/RedSolenoid 6
1020Blue/Wht/Red10s Chime coil
1121Org/RedKnocker coil
128Blue/RedOuthole coil
1317Brn/WhtDS9 - Strobe 9
1415Org/WhtDS8 - Strobe 8
1516Blue/WhtDS7 - Strobe 7
1614YelDS6 - Strobe 6
1713PurpleDS5 - Strobe 5
1810GreenDS4 - Strobe 4
197BrownDS3 - Strobe 3
206OrangeDS2 - Strobe 2
215BlueDS1 - Strobe 1
2224Not UsedNot used
2323Red+5 VDC
2422BlkGround


2g. Permanently Defeating the Slam Switch.

    Gottlieb used two slam switches in their pinball games and BOTH must be CLOSED or the game will not function. If you turn the game on and the displays come on IMMEDIATELY with all zeros (no five second delay and no relay "Click-Click"), this usually indicates one of the slam switches are open. If either of the two slam switches are open (one being the ball tilt roll switch), the CPU board will be "slammed", and a game cannot be started. Remember the normal System1 boot sequence: power-on, score displays dark, after 5 seconds the two under the playfield relays "click" and the score displays come on. If this 5 second boot-up delay is not seen, this is often because a slam switch is open. Also the score displays "roll" when the game is slam tilted. This can often be caused by the CPU board with connector problems, usually due to battery corrosion at the J6 connector, which goes to the slam switches.

    Below is a short 18 second video showing how the score displays should look in a normally booted and ready to play game. Versus how the score displays look on a slam tilted game.

    There is one slam switch inside front door around the lock, and one at the ball roll assembly at the left inside cabinet. Both these must be Normally Closed or the game will turn on the score display instantly with all zeros (no normal 5 second boot-up delay). Also you may see the score displays showing a wave like this "O0O0O0" then "0O0O0O" right to left. Again this shows a slam switch is open.

The coin door showing the normally closed Slam switch.

The ball roll and pendulum tilt switches on a system1 game. The
ball roll tilt switch must be CLOSED for the game to even "boot".

    Note the Tilt switch and the Slam switch are different! The Tilt switches (like the pendulum tilt, right below the ball roll assembly inside the cabinet) are Normally Open. There is also another weighted tilt switch mounted under the playfield. These tilt switches should be OPEN, where the two Slam switches are CLOSED. This is confusing because, for example, inside the cabinet at the left is the tilt pendulum which is open, and a slam switch on the ball roll right above it is closed.

Permanently defeating the slam switch circuit on the MPU board with a jumper wire
that shorts to two leads of capacitor C2.

    Because the slam switches go thru connectors and a lot or wiring to get to the switches, it is best to defeat the slam switches entirely. This can be done on the MPU board: short to ground the junction of R12 and C2 (or just run a jumper around capacitor C2, shorting its two legs).

    As an ending note, if the coin door coin switches' lockout wires are shorted to ground, this can cause a problem where the game looks to be "slammed tilted", even if the C2 modification is done. The lockout wire can easily touch the blades of the coin door switch, essentially shorting the coin door switches to ground. This really causes some weird behavior, making the game look like it's slam tilted.


2h. Adding LEDs to the Circuit Boards.

    One thing that Gottlieb never did was use LEDs on their circuit boards. Since Bally and Williams have spoiled me with this, as has Steve Charland (he turned me on to adding LEDs to system80 pop bumper driver boards), I've gotten the itch to add LEDs to some of the system1 circuit boards. We talked about this a little above in the CPU board repair section. (Adding +5 and -12 volt LEDs, and an "alive" LED to the CPU board.)

Added +5 and -12 volt LEDs to a system1 CPU board.

    Adding +5v and -12v Power LEDs to the CPU board.
    I personally find it nice to have LEDs showing that +5 volts and -12 volts is at the CPU board. Using two LEDs and 150 ohm and 560 ohm resistors, it's easy to add a couple LEDs to the CPU board next to the main power connector. You will have to drill a pair of 1/16" holes for each LED, but there's plenty of room to do this by the CPU board power connector. The +5 volt LED needs the 150 ohm resistor as a load, and the -12 volts needs the 560 ohm resistor. Note the resistors can be mounted on either the power or ground side of the LED. It is important to connect the flat side of the LED correctly or the LED won't work. (See the picture below.) Also note the -12 volt LED is wired "backwards" because it's a negative voltage.

The back side of the CPU board where the LEDs are connected to +5 and -12 volts.

    Adding a +5 volt LED to the Driver board.
    This is another easy LED addition which shows that +5 volts is getting to the driver board. Just need an LED and a 150 ohm resistor. Drill two 1/16" holes on the right edge of the driver board. Connect the flat side of the LED to the 150 ohm resistor, and the other end of the resistor to ground. Connect the non-flat side of the LED to the +5 volt trace. You're all done!

Right component side of the driver board with the added +5 volt LED.

Solder side of the driver board showing the added LED and resistor.

    Another LED I like to add is on the power supply. A good LED is for the 60 volts (which ultimately becomes 42 volts too.) Note I don't add a +5 or -12 volt LEDs, because those are already on the CPU board, and just seems redundant. (The CPU LEDs are not only showing the +5/-12 volts are present from the power supply, but that the connectors from the power supply to the CPU board are good too.)

    To add an LED to the 60 volt on the power supply, the easiest way to do this (without taking the power supply apart) is to connect the LED directly to the base of the J3 pin1 (60 volt) and J3 pin5 (ground) connector pins. Also a 10k ohm resistor is needed along with the LED (flat side of the LED going to ground.) Note it should use a higher watt resistor, as it's sinking like 58 volts to power the 2 volt LED. So a 10k ohm 1/2 watt resistor works well. Alternatively going to 15k ohm 1/2 watt resistor would probably be OK. (Though I've been running the set up below without problems, but the resistor does get hot.) Picture below...

Added LED for the 60 volts on a system1 power supply.

    If you have a Rottendog power supply, this modification can be made on their power supply too! Connector J3 pin1 is used for the 60 volts, and the large ground plane just above this connector is used to attach the 10k ohm 1/2 watt resistor to the flat side of the LED.

Added LED for the 60 volts on a system1 power supply.

    Adding LEDs to the Bottom Board (for fuse verification.)
    In addition to the LEDs on the circuit boards, you can also add a couple LEDs to the bottom board too. Specifically for the CPU controlled lighting and coil voltages. I put the fuses right on the two bridge rectifier, across the "+" and "-" lugs (along with a resistor.) This gives verification of the two accompanying fuses for these bridges. On the left bridge (for the CPU controlled lamps), use a 470 ohm 1/4 watt resistor. For the right bridge (coil power), use a 5.6k resistor 1/2 watt. Remember the flat side of the LED goes to the negative bridge rectifier lug.

Added LEDs on the CPU controlled lamp bridge rectifier and coil power bridge rectifier.
If their accompanying fuses are blown, the LEDs will not be lit.


2i. Video Showing the Gottlieb System1 Pinball "Oddities"

    The following 9 minute video describes what makes working on Gottlieb system1 pinball games different than other manufactures. That is, why a lot of repair guys just don't like working on these first generation Gottlieb solid state pinball games.


2i. Power On a Gottlieb System1 Pinball for the First Time
Note there's a VIDEO at the end of this section.

    When ever I get a new System1 game, there is a certain systematic approach I use to power up the game for the first time. I especially do this in cases where the game clearly has not been turned on for a long time, and its electronics are in unknown condition. I use this approach because having a bad power supply can richocette through the circuit boards, causing more damage than you started with (because there's no "crowbar" 5 volt protection). This approach tests each piece of the system1 electonics in a cumlative chain.

    Initial Board Identification and Power Chain.

    The general power chain works like this:

    1. Power in through the line cord. This then goes through a EMI filter, and then to the main line fuse. This is all on the lower bottom panel.
    2. Transformer, bridge rectifiers, fuses in the bottom of the cabinet. The 120 volts AC goes to the transformer and is diced into voltages the game needs. Basically there are several groups of voltages: display (69 volts DC), game logic (5/-12 volts DC), solenoids (25 volts DC), CPU controlled lamps (6 volts DC), general illumination (6 volts AC).
    3. After the transformer creates these distinct AC voltages, they are rectified (converted from AC to DC) on the lower panel using two bridge rectifiers. The exception to this rule is the display voltages which are rectified by the power supply board using discrete 1n4004 diodes. There is a fuse associated with each of these voltages on the bottom panel.
    4. Power for soleniods and CPU controlled lights and General illumination is routed to the playfield.
    5. Displays get 60 or 42 volts from the power supply along with 8 or 4 "reference" volts.
    6. CPU board gets 5 volts and -12 volt from the power supply.
    7. Driver board gets 5 volts from the CPU board.

    Step One: Power off, Check the Lower Board Fuses & Bridges.
    With the game off remove each of the fuses one at a time and test with a Multimeter (DMM) set to continuity. If a fuse is blown, just don't replace it (just yet). Fuses often blow for a reason. Note what the fuse does (there should be labels for each of the fuses).

    If for example the fuse for the CPU driven 6 volt lamp power is blown, test its accompanying bridge rectifier (because if the bridge is shorted, its accompanying fuse will blow). There's only two bridge rectifiers in a system1 game (25 volts coil power, 6 volts cpu driven lamp power.)

    If the 69 volt fuse for the score displays is blown, this often means one of the power supply's four 1N4004 diodes used for rectifying this voltage is shorted. If a 6.3 volt general illumination lighting fuse is blown, that can often mean a shorted light socket on the playfield.

    Now that the lower fuse panel is all checked out, REMOVE the 25 volt solenoid fuse before proceeding! Set it aside for later.

    Step Two: Power off, Check Playfield Coil Resistance.
    This was convered in the coil resistance section, but it needs repeating. If a driver board transistor shorted or there is a ground issue, a coil can lock-on and burn. If this is the case, either cut the non-banded diode lead going to the coil, or replace the coil. I do this before initial power-up. Because a burned (shorted) low-resistance coil can damage the driver board.

    Step Three: Isolate the Power Supply.
    This simply involves removing the top J2 and right J3 power supply connectors. (The top connector supplies 5/-12 volts to the CPU and driver board, the right side connector supplies display voltages to the score displays.) Only the bottom J1 power supply connector is attached (makes sure it's attached properely too, because this connector can be reversed!) Now turn the game on. The power supply's top connector J2 can be checked for +5 and -12 volts DC. The right side connector J3 can be checked for 60, 42, 8 and 4 volts DC. (The power supply board is screened with the voltage outputs for these connectors.) If any voltages are missing, you will need to repair the power supply before continuing. (More information on that can be found in the Power Supply section.)

    Step Four: Power Up with the CPU board Only.
    Now that the power supply checks out, the CPU board can be added to the mix. All CPU connectors can be removed except for the left most J1 (power) connector. Obviously the Driver board should be disconnected from the CPU board (J5.) Also remove the two right side CPU connectors J2 and J3 (which go to the score displays.) Disconnect J6 and J7 (switch matrix) connectors too.

    If you haven't done the ground modifcation to the CPU board, now is the time to do that.

    Power the game up, and test for 5 volts and -12 volts on the CPU board. Test for voltage at capacitors right next to the J1 connector, with a DMM test leads connected to the legs of the caps. Capacitor C16 (top electrolytic) is for +5 volts, and C17 is for -12 volts. The 5 volts should still be 5 volts (that is, the CPU board is not dragging down the 5 volts because of a shorted component). Note that the 5 volts is adjustable on the power supply, so adjust 5 volts to be 5.10 volts. The -12 volts should also be present.

    If the 5 volts checks out (4.95 to 5.20 volts DC) and the -12 volts is good, turn the game off. Now add the two score display connectors on the right side of the CPU board J2 and J3. (Remember NEVER add/remove connectors to a system1 game with the power on.) Have only ONE score display connected. Power up and the lone score displays should come on. If the lower left CPU connector J6 is removed, the display will come on immediately in "slam tilt" mode. If the CPU coin door J6 connector is attached, there should be a five second delay, then the score display will come on. (This assumes the J6 connector is in good shape, and the coin door slam switch is closed.) Note the immediate "slam tilt" mode causes the score display to "strobe." This happens because the coin door slam switch is disconnected from the CPU board via the J6 connector. In either case, the CPU board appears to be "booting" and operating. If nothing appears on the score display, the CPU board is "dead", and you'll need to repair or replace it.

    Assuming the CPU board is booting, turn the game off and connect another score display. Power on and see if the next display is working. If so continue powering off, adding another display, and powering back on. Do this until all the displays are connected and checked. A problem display can crash the system. So you'll know it when/if you connect a bad score display!

    Step Five: Power Up with the Driver board.
    There should be only three connectors not attached to the CPU board at this point (J5 for the driver board, and J6/J7 for the switch matrix.) With the game off, add the J5 driver board connector to the CPU board. It provides data and power to the Driver board. Remove all the connectors from the bottom of the driver board.

    If you haven't done the ground modifcation to the driver board, now is the time to do that.

    Install the 25 volt coil fuse into its fuse holder on the bottom board. Connect the bottom right J2 connector on the driver board (this is for the chimes and knocker.) Power the game on and see if there's any issues. Everything OK? Power off and add driver board connector J3 (lamps.) Power back on. Everything OK? Power off and add connector J4 (coils.) Power back on. Everything OK? Finally add driver board connector J5 (more lamps), and power back up. Hopefully everything is OK. If not, then you have some driver board work to do.

    Note that if any coils immediately "lock on" (energize) when power is turned on, turn the game off! This means there's issues with the driver board (or under-playfield mounted transistors), and that will need to be fixed before proceeding.

    Step Six: Check for coil voltage on the switch matrix connectors.
    If none of the coils lock-on when the game is turned on, things are good. But there's one last test. There could be a short from the coil voltage to the switch matrix. (That's why CPU connectors J6 and J7 aren't connected.) Using a DMM set to DC voltage, probe the pins of connectors J6 and J7 with the red DMM lead, and the black DMM lead connected to ground. You're looking for 25 volts on any of these pins. If you find it, that means there's a problem on the playfield where coil voltage is getting to switch matrix. That will FRY the CPU board. So that needs to be fixed before connecting CPU connectors J6 and J7. No coil voltage on the J6/J7 CPU connectors means you can add those back to the CPU board, and power up again.

    Step Seven: Run diagnostics.
    Now the game has pretty much checked out. But there's one last test, game diagnostics. With power on, the coin door diagnostic button can be pressed and diagnostic test 11,12,13 (displays, lamps, solenoids, switches) can be run. Test 11 and 12 is for the score displays. Test 13 will turn on all the CPU controlled lights for 5 seconds, then will cycle the 8 CPU controlled coils (including the 10,100,1000 point sounds), and allow you to test the playfield switches. (Note if no playfield switch is activated within 5 seconds, the game will go back to attract mode.)

Movie on First Time System1 Power up.
The following 13 minute video shows a systematic way to power on a Gottlieb system1 pinball for the first time. Did you buy a game in unknown condition out of a warehouse? Then this video shows you how to power it up, piece by piece, diagnosing problems along the way. This procedure is the best way to figure what is wrong with your game, before you do any significant work or worry with the machine.



3a. Fixing the CPU board.
    Much of this information thanks to Leon. I've taken his info, reworded it and added a bunch of comments and notes.

    Initial CPU Checking.
    There are a couple of things that should be noted right off when trying to fix an original non-working Gottlieb System 1 CPU board. First, is there any battery corrosion on the CPU board? If so, stop now and fix this by going here. The corrosion needs to be removed, neutralized, and any broken traces and corroded parts repaired and/or replaced. This will especially be an issue around the Z6,Z7 chips (to the right of the battery) and Z8,Z28 chips (to the left of the battery). All bets are off until a corroded CPU board is fixed. After any questionable parts are replaced, be sure to use a DMM set to continuity and check all the related board traces. Even one broken trace can definitely make a CPU board not work.

    Second, is there 4.95 to 5.2 volts DC at the CPU board? Best place to check for this is at the C16 capacitor (top most cap next to the the J1 power connector). Is there -12 volts DC at the CPU board? Best place to check for this is at the C17 capacitor (right below the C16 cap) next to the J1 power connector. The machine will absolutely not boot without +5 and -12 volts.

    Assuming the above voltages are correct, next check the score displays. Do they come on right at power-on and "strobe"? If so, there is a problem with the normally closed Slam switch. The CPU board should be modified so the useless Slam switch is not an issue (see here for details on that).

    Last, do the score displays come on after the game is powered on for 5 seconds? They should, as this is the normal system1 boot sequence. If they don't, then the CPU board is indeed "dead". If the CPU board turns on the score displays after 5 seconds of power, that is a good sign that the board is at least trying to boot.

    Also set the CPU board DIP switch as follows:

    • DIP 1-8=off (one coin, one credit).
    • DIP 9=on (three balls per game).
    • DIP 10=on (match feature on).
    • DIP 11=on (replay instead of extra ball).
    • DIP 12=on (tilt kills current ball only).
    • DIP 13=on (show number of credits).
    • DIP 14=on (play a tune when game started).
    • DIP 17,18=on (maximum credits 15).
    • DIP 20=on (chimes/tones when scoring).
    • DIP 21=on (show high score to date).
    • DIP 22=on (award 3 credits when high score beat).
    • DIP 23=on (play a tune when money inserted).
    Having the switches in these positions will make troubleshooting a bit easier and consistent from board to board.

    Adding +5v and -12v Power LEDs to the CPU board.
    Though this modification certainly doesn't fix a dead CPU board, I personally find it nice to have LEDs showing that +5 volts and -12 volts is at the CPU board. Using two LEDs and 150 ohm and 560 ohm resistors, it's easy to add a couple LEDs to the CPU board next to the main power connector. You will have to drill a pair of 1/16" holes for each LED, but there's plenty of room to do this by the power connector. The +5 volt LED needs the 150 ohm resistor as a load, and the -12 volts needs the 560 ohm resistor. Note the resistors can be mounted on either the power or ground side of the LED. It is important to connect the flat side of the LED correctly or the LED won't work. (See the two pictures below.)

Adding two power LEDs to the CPU board for +5 and -12 volts.

The back side of the CPU board where the LEDs are connected to +5 and -12 volts.

    Booting the CPU board on the Workbench.
    At this point, it's a lot easier to diagnose and fix the CPU on the workbench (instead of in the game). The best way to do this is using a computer power supply. The only voltages needed to boot the CPU board are +5 and -12 volts DC. So any computer power supply that outputs these voltages should work fine. Connect the computer power supply to the J1 (left side) CPU power connector:

    • A1J1 pin 1 (bottom most pin): not used.
    • A1J1 pin 2: -12 volts DC.
    • A1J1 pin 3: ground
    • A1J1 pin 4: ground
    • A1J1 pin 5: +5 volts DC.
    • A1J1 pin 6 (top most pin): +5 volts DC.

    Another perhaps easier way to connect the voltage from the computer power supply to the CPU board is using the C16 (top most) and C17 (below C16) capacitors next to the J1 power connector:

    • C16 top cap, top lead: +5 volts DC
    • C16 bottom lead: ground
    • C17 bottom cap, bottom lead: -12 volts DC

    Installing an "Alive" LED.
    Now the next problem to overcome are the score displays, or the lack of score displays. Since we can't use score displays on the workbench, we need some way to tell if the CPU board is "booting". When mounted in a game this is easy, as we turn the power on, wait 5 seconds, and then the score display should turn on (indicating a proper boot sequence). Yet on the workbench we can't do this.

    Instead we use an LED and a resistor connected to chip Z16 pin 15 (upper right most chip on the CPU board). Just a water clear style LED (that's important that it's a water clear style) and connect the flat side to a 150 ohm resistor. Connect the other side of the resistor to ground (Z16 pin 8.) Now connect the non-flat side of the LED to Z16 pin 15. When the CPU board is powered-on, after a 5 second delay, the LED should light up (just like a miniature score display). If we can get our CPU board to light this LED after a 5 second delay, this is our indication that the CPU board is "running". Since the CPU board is in attract mode, the LED will dim when the game switches shows the high score to date in all the score displays. Likewise the LED will be brighter when just the last game played ("000000") shows in just the player1 score display.

    So if you have gotten this far, and the board is booting, you can skip down to the Testing the Buffer and Spider Chips. Otherwise keep reading...

Alive LED: Connect a 150 ohm resistor to chip Z16 pin8 (gnd), with the
other side of the resistor going to the flat side of an LED. Then attach
the non-flat side of the LED to Z16 pin15. Adding this LED gives the CPU board
an "alive" LED, which lights when the score displays turn on, indicating a
booting CPU board.

Here's a different way to install the "alive" CPU board LED. This LED
is mounted with two drilled 1/16" holes, and the 150 ohm resistor going
to z16 pin15 and ground on the back of the CPU board.

 

    Note on some games I have added the "alive LED", and I have the CPU working and installed in an actually pinball machine, there was one segment on the score displays that did not work. This one segment would be on player1, player2, and the credit display. This only happens on some machines, and I'm not entirely sure why. I've used the "alive LED" on a great many CPU boards, yet once installed in some games, I have this one display segment missing issue. The solution is to just remove (or disable) the "alive" LED once you have the CPU board working in your game.

    Dead CPU: Next Steps.
    The CPU board is completely dead, with no score display activity after 5 seconds of power-on. Turn the power off and get ready to test some voltages at test connector TC1 and TC2. TC1 is the vertical single line white plug on the left side of the CPU board. TC2 is the vertical white plug in the dead center of the CPU board. On both TC1 and TC2 pin1 is the top most pin.

      Reset Circuit: The reset circuit holds the CPU chip low for a set period of time until the +5 volts can stablize. If the CPU chip is never told to go "high" from the reset circuit, the board will never start to boot.

      Measure TC1 pin 14 (or chip Z2 pins 7,9) and power the CPU on. It should show immediately at power on -12 volts. This will rapidly change into +5 volts after about half a second. This is the RESET signal. Another place to check the Reset is at chip Z2 pins 7,9. (Both should go high to 5 volts after about one second of power-on.) If the reset is not working and does not change to +5 volts, it is best to replace the Q5 and Q6 (MPS-A70) in the reset circuitry. If the reset is still not going from -12 to +5 volts, change chip Z2 (4528 CMOS.) Still not working, check or replace caps C31 and C32 (.1 mfd, and these do sometimes fail). Note that the "Reset" button on the CPU board has nothing to do with this Reset signal (it is only used to reset bookkeeping values).

Reset components on the CPU board.
From actual Gottlieb documents, so it's their property.

      Gottlieb revised the RESET circuitry during System1 production. The new version gives a longer Reset and ensures the CMOS RAM is locked out quickly at power-off. Older boards can be upgraded if desired.
      • R159 Change 2.7meg to 3.9meg ohms
      • R160 Remove.
      • R161 Change 27k to 43k ohms
      • R162 Change 6.8k to 2k ohms
      • R163 Change 27k to 6.8k ohms

      Clock Circuit. The next thing we check are the clock signals. The clock circuit provides the timing the CPU chip needs to execute. This is provided by the CPU board crystal and the U1 spider chip.

      Check TC2 pins 11,12 using an oscilloscope or a logical probe, and there should be pulsing signals. Also check both legs of the crystal, and the same pulsing should be seen on both legs. If an o'scope is not available, use a DMM set to DC volts. This should show 2.8 volts at TC2 pin11 and 2.9 volts at TC2 pin12. The top leg of the crystal should show .3 volts, and the bottom leg should show .9 volts. If there are no clock pulses, there is a problem with the Rockwell U1 spider chip, and the story ends here (as the spider chips are no longer available). The only choice is to buy a new NiWumpf or Pascal CPU board. There is a chance the crystal (above the J1 power connector) is bad, but that is unlikely (but it does happen). Crystal Y1 is a 3.579 MHz crystal.

      Address/Data Line Activity. Now that we have a reset and clock circuit, check the address and data lines for activity. This is done at TC1 pins 1-13. Use an o'scope or logic probe looking for pulsing lines. If there's no pulsing, the Rockwell spider chip(s) are bad, and again the story ends here (buy a NiWumpf or Pascal CPU board). If pulsing is seen at TC1 pins 1-13, then it's time to move to the next step.

      Score display LED On?
      At this point the CPU board should be booting on the bench. This can be seen by viewing the LED we added to simulate the score displays coming on. With the Slam switch defeated, there should be a 5 second delay after power-on, and then the added LED should light. If this is the case, we can now move to testing the Spider chips and Buffer chips. If this LED is not coming on, and all the above tests check out good, it's time to buy a NiWumpf or Pascal CPU board.

      Testing the Input/Output Buffer and Spider Chips. In order to check the buffer chips, we will activate the buffer inputs, and see if there is a corresponding response at the buffer outputs. The buffers chips are Z29 (7405) and Z27 (74H21), both right below the DIP switch. Also Z9 (7405) and Z8 (7404), both at the bottom left of the CPU board. Use an alligator clip connected to ground to activate the buffer inputs, which will control the buffer output pins. A logic probe is best for checking the output, but a DMM set to DC volts can be used.

        Ground Z29 pin 1 (input) and check pin 2 (output).
        Ground Z29 pin 5 (input) and check pin 6 (output).
        Ground Z29 pin 11 (input) and check pin 10 (output).
        Ground Z29 pin 9 (input) and check pin 8 (output).
        All outputs should show +5 volts.

        Ground Z27 pin 1 (input) and check pin 2 (output).
        Ground Z27 pin 3 (input) and check pin 4 (output).
        Ground Z27 pin 5 (input) and check pin 6 (output).
        Ground Z27 pin 9 (input) and check pin 8 (output).
        Ground Z27 pin 11 (input) and check pin 10 (output).
        Ground Z27 pin 13 (input) and check pin 12 (output).
        All outputs should show +5 volts.

        Switch Matrix Returns:
        Ground Z9 pin 1 (input) and check pin 2 (output).
        Ground Z9 pin 3 (input) and check pin 4 (output).
        Ground Z9 pin 5 (input) and check pin 6 (output).
        Ground Z9 pin 9 (input) and check pin 8 (output).
        Ground Z9 pin 11 (input) and check pin 10 (output).
        Ground Z9 pin 13 (input) and check pin 12 (output).
        All outputs should show +5 volts.

        Switch Matrix Returns:
        Ground Z28 pin 3 (input) and check pin 4 (output).
        Ground Z28 pin 11 (input) and check pin 10 (output).
        All outputs should show +5 volts.

      If any input is grounded and it's associate output does not respond (by going to +5 volts), the chip is bad.

        Switch Matrix Strobe. Best to use a logic probe for this:
        Z8 pin 1/2 = Strobe0: both pins pulsing.
        Z8 pin 3/4 = Strobe1: both pins pulsing.
        Z8 pin 5/6 = Strobe2: both pins pulsing.
        Z8 pin 9/8 = Strobe3: both pins pulsing.
        Z8 pin 11/10 = Strobe4: both pins pulsing.
        Z8 pin 13/12 = Strobe5: both pins pulsing (not used in any system1 games).

      If the logic probe shows pulsing just on the input side of the Z8 7404 (first pin listed above) and not on the output pin, then the 7404 chip at Z8 is bad. If incorrect activity (no pulsing) is seen on the input side of the Z8 7404 chip, then the U5 spider chip is bad, and the story ends here.

      Now we can test the solenoid buffer chips at Z6 and Z7 (7417). The 7417 chips at Z6 (located just above connector J5) and Z7 (to the right of Z6). The U4 spider chip sends signals to the Z6/Z7 buffers, which then signal the driver board transistors at Q25-Q32 for the CPU controlled coils. With the CPU board power on, attach an alligator clip to +5 volts (the positive/upper lead of capacitor C16 on the CPU board). Then touch the Z6 input pins (one at a time) with +5 volts, and watch the output pin:

        Z6 pin 1 (input) and check pin 2 (output)
        Z6 pin 3 (input) and check pin 4 (output)
        Z6 pin 5 (input) and check pin 6 (output)
        Z6 pin 9 (input) and check pin 8 (output)
        Z6 pin 11 (input) and check pin 10 (output)
        Z6 pin 13 (input) and check pin 12 (output)

        Z7 pin 1 (input) and check pin 2 (output)
        Z7 pin 3 (input) and check pin 4 (output)

      So once the solenoid buffer chips are tested, we need to have some way to test the U4 spider chip (which sends solenoid signals to Z6/Z7). It is impossible to control all the outputs of U4 on the bench, but if we control some of them. If the U4 works for the ones we can control, it will probably be OK for the rest. We can use the machine's "play-a-tune" feature when a coin switch is activated (make sure DIP switch 23 is "on"). If we can simulate a coin switch closure, the U4 spider chip will send signals to the Z6 chip, activating the three chime coils (or sound board triggers). We can see this with a logic probe at the Z6 chip.

      To simulate a coin switch closure, Use a jumper wire and connect one end to chip Z8 pin 4. With the other end momentarily touch Z9 pin 1. This simulates a coin drop by momentarily touching switch matrix strobe1 to return0. Using a logic probe, check the following Z6 solenoid buffer chip pins which the U4 spider chip toggles:

        Z6 pin 5 (ten point chime).
        Z6 pin 9 (hundred point chime).
        Z6 pin 11 (thousand point chime).

      You should see the above pins go high as the coin switch closure is simulated. If any one of the above pins do not go high, the U4 spider chip is bad. Since there is no replacement available for the U4, the CPU board is junk and must be replaced.

    The only thing not tested on the bench is the U6 spider chip and Z16/Z17 7448 chips that control the score displays. This spider rarely fails, and it is very easy to test the displays using the game's built-in diagnostics. So there really is no need to do this on the workbench.

    CPU Considerations (Spider chips, etc).
    The Rockwell PPS-4/1 and PSS-4/2 system was a 4-bit parallel processing system with two CPU "spider" chips that communicate with each other (U1 11660-CF was the main processor, and U2 10696-EE was the second processor). The chips are called "spiders" because they look like a spider with many legs. The spider chips were a wider chip package, almost a square chip. System 1 used six of these custom spider chips labeled U1 to U6: two for the CPU (U1/U2) and one each for the switch matrix (U5 A1752-CF), solenoid control (U4 A1753-CE), and score displays (U6 10788-PA). The last spider chip (U3, also a 10696-EE chip, same as the second CPU processor at U2) was used for lamps and a few switches and left over duties. Both the switch matrix (U5, A1752-CF) and solenoid control (U4, A1753-CE) spider chips have built-in ROM software. Display output was controlled by the U6 spider chip (10788-PA). The switch matrix has eight rows (R0-R7) and five columns (S0-S4), for a total of 40 switches. These are all driven by chips Z8 (strobes/columns, 7404) and Z9/Z28 (rows, 7405).

Two System 1 CPU board spider chips and the game PROM ("C" means Joker Poker).
The added red wire to cap C16 negative lead is part of the ground modifications.
Note the two "spider chips" shown in this picture.

    The solenoid control (U4, A1753-CE) and switch matrix (U5, A1752-CF) spider chips are notorious for failing easily. The solenoid control spider dies from locked on coils due to driver transistor failure. The switch matrix spider dies from coil voltage being shorted to the switch matrix. The two CPU spiders (U1 11660-CF and U2 10696-EE), the display spider (U6, 10788-PA) and the U3 (10696-EE) spider rarely fail. Unfortunately none of the spider chips are available, hence replacement CPU board have been created by Ni-Wumpf and Pascal Janin).

    Here's a summary of the spider chips:

    • U1, 11660-CF (CPU)
    • U2, 10696-EE (CPU)
    • U3, 10696-EE (misc lamps and switches). Same as U2 spider
    • U4, A1753-CC,CE,EE (solenoids, often fails)*
    • U5, A1752-CD,CF,EF (switch matrix, often fails)*
    • U6, 10788-PA (display)

    * Note that spider chips U4 or U5 contain the game operating system ROM, and must be of the same revision. These are the two spiders that fail the most. The revision levels that work together are:

    • U4 A1753-CC works with U5 A1752-CD
    • U4 A1753-CE works with U5 A1752-CF
    • U4 A1753-EE works with U5 A1752-EF

    Socketing Spider Chips.
    If you are lucky enough to find NOS (new old stock) spider chips (or have boards to steal them from), these old spiders need to be removed and the new spider installed. Removing these is standard desoldering. But a new CPU spider chip should probably be socketed on the CPU board.

    To do this, buy some SIP (single inline pin) machine pin sockets, and solder them into the board. This way the spider can be pluged into the SIP sockets. As a note of caution, it's best to "double up" the SIP sockets (as shown in the picture below). This is done for two reasons. First so the spider legs (which are somewhat wide) don't stretch the SIPs soldered into the board. That is, if the spider legs cause problems, they will ruin the easy-to-remove SIPs on the legs, not the SIPs soldered into the CPU board.

    The second reason to "double up" the SIPs is to aid in the installation of the spider chip into the board-mounted SIPs. Aligning all the spider chip pins is tricky. But if extra SIPs are installed on the spider chip first, installation of the spider chip into the board-mounted SIPs is *much* easier.

A socketed Spider chip on a CPU board. Note the use of "doubled up" SIP sockets.
Picture by Scott.


3b. Game ROMs, PROMs, EPROMs and Test PROM.

    The game PROM at Z23 is a 18 pin PROM which contains the game specific rule computer code for the CPU board. This bipolar PROM is not duplicatable in its native form, as blank PROMs are long gone. Also nearly long gone is any sort of PROM programmer that would program a blank (if one could be found). Add to this that the bipolar PROM at Z23 is often bad (it runs very hot, even when working properly), and this becomes a problem for a System1 CPU board.

    Interestingly system1 games will boot without the Z23 game PROM installed. Because the majority of the system code is inside the "spider" chips, the game PROM is not needed to boot a system1 CPU board. Diagnostics/audit can even be run with no Z23 game PROM installed. The game can be coined up. But if a game is started with no Z23 Game PROM installed, the start-up sounds will play, and then the game will lock up.

    Using a 2716 EPROM for the Game PROM at Z23.
    A 24 pin 2716 EPROM can be used instead of the 18 pin bipolar PROM at Z23. But to do this a couple things are needed. First an adaptor board must be purchased or made. Pascal Janin sells an adaptor board. Next the Gottlieb system1 PROM images must be formatted for a 2716 EPROM (available here in a ZIP file - updated 10/20/06 as the Buck Rogers code was bad).

    Ni-wumph's main game 27256 EPROM and board manual is available directly from Niwumpf's support web page. The Niwumph EPROM image is also available here and the manual here for convenience. Schematics for Niwumpf are also available here, here, here.

    Making a 2716 EPROM Adaptor for the Game PROM at Z23.
    The original Gottlieb System1 Game PROM is a bipolor PROM with a 1024 x 4 bits size. These are no longer available in programmed or blank format. Even more rare is the type of hardware that does the programming for these obsolete bipolar PROMs.

A system1 PROM to 2716 EPROM adaptor board layout (from Leon Website).

System1 Game PROM to 2716 EPROM adaptor boards.

    To get around this problem, the Pascal Janin and PinLizard used to sell an adaptor that allowed for a 24 pin 2716 EPROM to plug into the smaller 18 pin bipolar PROM socket on the CPU board. Unfortunately the PinLizard version is no longer sold (but the Pascal Janin version is still available.) You can also make your own adaptor using the cross information below. It just requires the data/address lines to be crossed from one socket type to the other, and an added .1 mfd capacitor between +5 volts and ground.

    • PROM pin 1 to EPROM pin 22
    • PROM pin 2 to EPROM pin 2
    • PROM pin 3 to EPROM pin 3
    • PROM pin 4 to EPROM pin 4
    • PROM pin 5 to EPROM pin 5
    • PROM pin 6 to EPROM pin 8
    • PROM pin 7 to EPROM pin 7
    • PROM pin 8 to EPROM pin 6
    • PROM pin 9 to EPROM pin 12,18,19,20 (ground)

    • PROM pin 10 to EPROM pin 13
    • PROM pin 11 to EPROM pin 11
    • PROM pin 12 to EPROM pin 10
    • PROM pin 13 to EPROM pin 9
    • PROM pin 14 to EPROM pin 12,18,19,20 (ground)
    • PROM pin 15 to EPROM pin 23
    • PROM pin 16 to EPROM pin 1
    • PROM pin 17 no connect
    • PROM pin 18 to EPROM pin 21,24 (+5 volts)

    Gottlieb System1 Test PROM "T".
    Because the internal diagnostics are somewhat limited for System1 games, Gottlieb also made a "T" bipolar Test PROM. These are very difficult (if not impossible) to find. But if you have a 2716 EPROM adaptor, you can download the Test PROM code in 2716 format and use the adaptor board.

    Using the System1 Test PROM.
    The Test PROM boots just like any other System1 game (this is because the boot code is actually in the spider chips, not in the Game PROM). The game will seemingly be in "attract mode" too with the "T" PROM installed. Pressing the Test button inside the coin door will yield the same audit/tests just like a game PROM was installed (or nothing was installed) at Z23. The tests are no different. Again this is because the audit/test code resides in the spider chips and not the Game PROM.

    To access the Test PROM start a game (no credits are needed, but you can add credits if you want, and the coin-up tune will play). As soon as a game is started the game start-up sounds will play (10,100,1000 point sounds or chimes coils 3,4,5) and then the outhole (coil1), the knocker (coil2), the outhole (again), and three game specific coils 6,7,8. While this is happening the Game Over relay will pull in for about two seconds and then release. All the coil energizing happens very fast at game start (the only coil that does not pull in is the Tilt relay). Also all 36 of the CPU controlled lights will turn on for about two seconds and then turn off. The CPU lights do this (starting with lamp #01 to lamp #36) in a quick progression.

    At this point the game's playfield switches becomes the Test PROM's input. All game switches (except for the two coin chute and credit button) have a test function. All the CPU controlled lamps should be off. Hitting a playfield switch should toggle a CPU controlled lamp on or off, and/or fire a solenoid. If the game has all 40 switches wired, all 36 CPU controlled lamps can be turned on (assuming the game uses all 36 lamps). You will need the game manual to know how a playfield is wired for this exercise, because you will need to know where each switch number is found on the playfield to determine what it controls. The slam switch or outhole switch will exit the "game" (test) mode and go back to attract mode.

Switch# Action Score Display
Sw #00 (test button) Lamp #01 (Game Over) Pulls in Game Over relay and switches to audit/diag mode.
Sw #01 Coin Chute 1  
Sw #02 Coin Chute 2  
Sw #03 Credit button Start Test/Add a player
Sw #04 (tilt) Lamp #02 (tilt)
Pulls in Tilt relay quickly
Can end the "game" (test) mode.
 
Sw #10 Coil 2 (knocker)
Toggles Game Over relay/lamp
 
Sw #20 Coil 3 (10 pts)
Toggles lamp Q3 (high score)
 
Sw #30 Coil 4 (100 pts)
Toggles lamp Q4 (shoot again)
 
Sw #40 Coil 5 (1000 pts)
Toggles lamp Q5
 
Sw #50 Coil 6
Toggles lamp Q6
 
Sw #60 Coil 7
Toggles lamp Q7
 
Sw #70 Coil 8
Toggles lamp Q8
 
 
Sw #11 Toggles lamp L9 Scores 10 by 1s when L9 lites
Sw #12 Toggles lamp L16  
Sw #13 Toggles lamp L23  
Sw #14 Toggles lamp L30  
 
Sw #21 Toggles lamp L10 Scores 90 by 10s when L10 lites
Sw #22 Toggles lamp L17  
Sw #23 Toggles lamp L24  
Sw #24 Toggles lamp L31  
 
Sw #31 Toggles lamp L11 Scores 900 by 100s when L11 lites
Sw #32 Toggles lamp L18  
Sw #33 Toggles lamp L25  
Sw #34 Toggles lamp L32  
 
Sw #41 Toggles lamp L12 Scores 9000 by 1000s when L12 lites
Sw #42 Toggles lamp L19  
Sw #43 Toggles lamp L26  
Sw #44 Toggles lamp L33  
 
Sw #51 Toggles lamp L13 Scores 90,000 by 10,000s when L13 lites
Sw #52 Toggles lamp L20  
Sw #53 Toggles lamp L27  
Sw #54 Toggles lamp L34  
 
Sw #61 Toggles lamp L14 Scores 900,000 by 100,000s when L14 lites
Sw #62 Toggles lamp L21  
Sw #63 Toggles lamp L28  
Sw #64 Toggles lamp L35  
 
Sw #71 Toggles lamp L15  
Sw #72 Toggles lamp L22  
Sw #73 Toggles lamp L29  
Sw #74 Toggles lamp L36  


3c. Built-in Diagnostics/Bookkeeping

    Inside the coin door there is a large white momentary switch that is known as the "play/test" button. Press this button to access the game audits and test modes. After the button is pressed, it takes about one second and then the audit number "0" will appear in the ball/credit display, signifying the first audit value. The value for the audit will appear in the score displays. As the test button is pressed, the ball/credit display will increment a number 0 to 13 indicating the test/audit number. If any audit number (0-10) needs to be cleared, press the CPU board mounted black "reset" button to clear the audit value. To exit the test mode, either open the Slam switch or close a Tilt switch.

    Note on the high score level replay values. Setting a "zero" at high score level means the level is not in use. But this does not apply to the High Game to Date score level (the zero does not disable this).

    While in audit/diagnostic mode, the Q (game over) relay will be energized. This means the flippers and pop bumpers and slingshots (non-CPU controlled) coils should work while the game is in audits.

The Gottlieb System1 coin door with the diagnostic entry switch.

    Here are the audit/test numbers and what they represent:

    Audits:

    1. Total coins thru coin chute #1.
    2. Total coins thru coin chute #2.
    3. Total plays.
    4. Total replays given.
    5. Number of slam tilts.
    6. Number of extra balls.
    7. Number of tilts.
    8. First replay score value.
    9. Second replay score value.
    10. Third replay score value.
    11. Current High Score to date.

    Diagnostics:

    1. Display test for player #1 and #3 score displays. Increment display values from "000000" to "999999" in player1 and player3 score displays.
    2. Display test for player #2 and #4 score displays. Note the credit display is *not* tested in either test #10 or #11.
    3. Lamp/Coil/Switch test: see below for description.

    Diagnostics.
    After advancing through all the audits (0-10) and the display tests (11/12), diagnostic #13 will engage. After a second, all CPU controlled lights come on for five seconds. That's not much time to find a CPU controlled light that is burnt out! But unfortunately there's no way to keep the #13 diagnostic in lamp mode for any longer than five seconds. And to re-engage the lamp mode will require exiting diagnostics (or power cycling the game), going thru all audit/tests 0 to 12, and then advancing to test #13 (for another five seconds of turned on lamps). This does not make for easy lamp testing.

    Another problem with the lamp test is lamps L3 and L4 (Q3 and Q4). On many System1 games, these two MPS-U45 transistors are used for the High Score to Date and Shoot Again lamps. Hence these two lamps (L3/L4) are tested in the lamp test (on for five seconds upon entering test #13). But on some System1 games Q3 and Q4 are used as pre-drivers to under-the-playfield mounted 2N5875 transistors. These in turn control a playfield solenoid. If this is the case, these two solenoids will energize for five seconds in the lamp test! Just keep that in mind.

    After the CPU controlled lamps are turned off, each CPU controlled solenoid is energized one at a time. Well not really all of the CPU controlled solenoids. For example, the T (Tilt) relay is not included in this test. Neither is the Q (Game Over) relay, which is already energized during the whole audit/test routine. But all the other ten solenoids (including three sounds/chimes) will be tested ONCE.

    Then the test moves to the switch matrix test. If there are no closed switches, after about 5 seconds the game will exit test #13 and go back to attract mode. If a closed switch is found, it will display in the ball/credit display. If you want to test a switch, do it now! Hurry up though. If no other switches are sensed as closed within a five second window, the game will exit the test mode and go back to attract mode. Also if you hold a switch closed, it takes about *two* seconds before that switch number appears in the ball/credit display! Talk about a slow CPU board.

    Overall the #11,#12,#13 Gottlieb System1 diagnostic tests are pretty lame. Especially compared to comparible Bally and Williams diagnostics of this era (1977-1980). Ideally it would be nice to flash all the CPU controlled playfield light on and off continually until the user wants to proceed. This cannot be done with the System1 diagnostics. Also again it would be nice to keep running the coil test over and over, and to keep the game in switch test mode until the user wants to exit. Unfortunately these things can't be done with the stock System1 diagnostics. This makes finding bad CPU controlled lamps, coils, and playfield switches more difficult.

    Another method of testing lamps, coils and score displays is to use a NiWumpf CPU board. The testing routines in the NiWumpf board are *much* better than the stock Gottlieb System1 tests. For example, CPU lights can be continually cycled on and off. Same thing with coils (and the Game Over and Tilt relays are activated too!) And the NiWumpf display test also tests the 4-digit ball/credit display (which the stock Gottlieb test does not). So using the NiWumpf to test a driver board works very well. The NiWumpf switch test operates as it should and is very quick to display a closed switch (but unfortunately this test cannot be used on a stock Gottlieb CPU board).

    The Z23 Game PROM and Diagnostics.
    Interestingly, a Gottlieb System1 CPU board does *not* need the game PROM at Z23 to run diagnostics! Because a lot of the system code for all system1 games is inside the "spider" chips, the game PROM is not needed to run diagnostics. The CPU board will boot up fine without the Z23 PROM. Heck you can even try and start a game (the chimes will sound, but then the game will lock up). So if you need to test a System1 CPU board and don't have a Z23 game PROM, no problem. Just boot the game and press the coin door diagnostic test switch. It will go through the audits and diagnostics whether the Z23 PROM is installed or not.

    Gottlieb Test PROM for Z23.
    Gottlieb also made its own Test PROM that installs at Z23 instead of the game PROM. This provides much better testing of a stock Gottlieb System1 CPU board. Unfortunately the original 6351 PROM is not readily available.


3d. Locked-on or Not Working Coils

    The driver board is largely responsible for controlling coils and lamps. Of course signals for this start at the CPU board, but ultimately if a coil does not work correctly, the driver board is a good starting point.

    Remember there's two different kinds of coils on a system1 game: CPU controlled and non-controlled. You'll need to know which type you're working with to further diagnose any coil problems. We'll be concentrating on the CPU controlled type of coils, as those are more difficult to diagnose and fix.

CPU controlled versus non-CPU controlled coils.

Diagnosing Coil Problems.

    Step 0: Coil CPU or Non-CPU Controlled?
    In the case of a non-working or locked-on coil, first figure out if the coil is CPU controlled. Pop bumpers, slingshots, coin door lockout and flipper coils are *not* CPU controlled. All other coils are controlled by the CPU.

    Next figure out which driver board transistor(s) control the coil in question. Remember there are system1 "dedicated" coils, which are the same for all system1 games. This includes the sound drives, knocker, and outhole. The remaining three driver transistors are game dependant. Add to that the possibility of two more under the playfield driver transistors (driven by a small driver board transistor like Q17/Q18), and there are a total of five possible game dependant CPU controlled coils (aside from the dedicated coils.)

Driver Board Transistor Overview
Coil# Description Transitor# Notes
1 Outhole Q32 (2n6043) Dedicated
2 Knocker Q25 (2n6043) Dedicated
3 10pt Chime Q26 (2n6043) Dedicated
4 100pt Chime Q27 (2n6043) Dedicated
5 1000pt Chime Q28 (2n6043) Dedicated
6 Game dependant Q31 (2n6043)  
7 Game dependant Q30 (2n6043)  
8 Game dependant Q29, Q45
(mps-u45,
2n3055)
 

Driver Board Transistor Detail
Trans# Position Type Pre-driver CPU Chip Usage
Q25 Far right 2N6043   CPU Z6 pin 3/4
to A1J5 pin 11
Knocker
Q26 2nd from rt. 2N6043   CPU Z6 pin 5/6
to A1J5 pin 10
10 Chime or Sound
Q27 3rd from rt. 2N6043   CPU Z6 pin 9/8
to A1J5 pin 7
100 Chime or Sound
Q28 4th from rt. 2N6043   CPU Z6 pin 11/10
to A1J5 pin 8
1000 Chime or Sound
 
Q32 Center Left 2N6043   CPU Z6 pin 1/2
to A1J5 pin 12
Outhole
Q31 2nd from Cnt Lft. 2N6043   CPU Z6 pin 13/12
to A1J5 pin 9
Solenoid #6 (game specific)
Pre-driver for under PF trans
Q30 3rd from Cnt Lft. 2N6043   CPU Z7 pin 1/2
to A1J5 pin 1
Solenoid #7 (game specific)
Pre-driver for Under PF trans
Q29
Q45
4th from Cnt Lft.
Center Right
MPS-U45
2N3055
Q29
CPU Z7 pin 3/4
to A1J5 pin 2
Solenoid #8 (game specific,
usually for a drop target reset coil.)
 
Q2 Far Left MPS-U45   CPU LD2, Z26 pin 3/4
to A1J5 pin 5
to SDB Z1 pin 5/7
Tilt (T) Relay
Q1 2nd from Far Left MPS-U45   CPU LD1, Z26 pin 1/2
to A1J5 pin 6
to SDB Z1 pin 4/2
Game Over (Q) Relay
Q3 (L3) 3rd from Far Left MPS-U45   CPU LD3, Z26 pin 5/6
to A1J5 pin 4
to SDB Z1 pin 12/10
used for CPU controlled lighting
(L3=High Game to Date).
Q4 (L4) 4th from Far Left MPS-U45   CPU LD4, Z26 pin 9/8
to A1J5 pin 3
to SDB Z1 pin 13/15
Used for CPU controlled lighting
(L4=Shoot Again).
Q17 (L17) 14th from Far Left MPS-A13   CPU LD1, Z26 pin 1/2
to A1J5 pin 6
to SDB Z5 pin 4/2
Pre-driver for under PF trans, as needed
Q18 (L18) 13th from Far Left MPS-A13   CPU LD2 Z26 pin 3/4
to A1J5 pin 5
to SDB Z5 pin 4/2
Pre-driver for under PF trans, as needed
 
Q5-Q24,
Q33-Q44
Top middle row MPS-A13   Z1-Z9 Used for CPU controlled lighting.
 
none under playfield 2N5875* 2n6043 (Q30,31) or
MPS-A13 (Q17,Q18)
Z1 SDB Playfield mounted Transistor(s)
(game specific)
 
none         Coin door lockout coil
connected directly to 25 volts.
* Buck Rogers used a TIP115 under the playfield.

The Gottlieb System 1 driver board transistor layout.
From actual Gottlieb documents, so it's their property.

The Gottlieb System 1 driver board transistor layout.

    Step1: Check for -12 volts at the CPU board.
    If many or all solenoids and CPU controlled lamps are constantly on or solenoids do not work at all, the problem could be missing -12 volts DC at CPU board. Of course without this voltage the game won't "boot" either. But check for -12 volts across CPU board cap C17 (below C16). If it is OK, the problem could be in the CPU board buffers Z6 and Z7 (7417) too (more on that later). When diagnosing a non-working game, it's best to removed the card edge connector going between the CPU and driver boards. This will ensure that no coils engage while you figure out why the game doesn't boot.

    Step 2: Check the Coil Resistance.
    This is very important. If a coil has a bad coil diode and/or low resistance, any work done to the circuit boards will be ruined when the game is turned back on (if it's a non-CPU controlled coil, the solenoid fuse will immediately blow if the coil is activiated). If any coil measures below 2.5 ohms, replace it. See the Checking Coil Resistance section for more details.

    Step 3: Check the Driver board to Coil Wiring (Connectors).
    This only applies to CPU controlled coils. With the game on and in game mode, use a DMM set to DC volts and check for power at both lugs of the coil in question. Power at only one lug means the coil is open (replace coil or re-attach broken winding). Power at neither lug suspect a bad solenoid fuse or the power "daisy chain" is broken up-stream.

    Now move up to the backbox, and attach one end of an alligator clip jumper wire to ground. Touch the other end of the jumper wire momentarily to the metal tab of the controlling transistor. This should fire the coil. (Note on Q29/Q45 controlling transistor pair, ground only the metal tab of the larger Q45, as grounding the small Q29 will yield nothing). If the coil does not fire, suspect a bad connector on the bottom edge of the driver board (or a broken trace on the driver board). If the coil fires, time to move to the next step and test the transistors and controlling chips, eventually moving all the way back to the CPU board.

    Connectors are a huge problem on System1 games, don't overlook them. The connectors along the bottom edge of the driver board *and* the connector that runs between the driver board and/or CPU board could cause a coil to not work. See the Connector section for more information on how to replace System1 connectors.

    Step 4: Verify if an Under the Playfield Transistor is used.
    Some later system1 games used one or two of the 36 driver board lamp transistors to control additional playfield solenoids. The low-voltage (6 volt) lamp transistors were wired to under-the-playfield mounted 2n5875 power transistors, which drove a hi-power 24 volt solenoid. Essentially the lamp driver transistor was a pre-driver for the larger playfield-mounted transistor, which ultimately drove a coil. These playfield mounted transistors added another level of complexity to the System1 design, and often confused operators.

    Interestingly several different pre-driver transistors were used for the under the playfield 2n5875 transistors. All on the driver board, some games used the small MPS-A13 (Q17, Q18) and others used a larger 2n6043 (Q30, Q31.) Generally if the item being controlled was a ball kicker or a drop target bank, the larger 2n6043 (essentially a TIP102) was used as the pre-driver. Also there was one odd exception to the use of the metal cased 2n5875 transistor under the playfield. That was on Buck Rogers where a TIP115 (NTE262, PNP) was used. (Note a TIP36c can be substituted.)

    Games with Under the Playfield Transistors
    Game Coil Designator Pre-Driver PF Driver
    Close Encounters Roto Target Sol.7 (Q30) 2n6043 2n5875
    Count Down Yellow drop target bank L17 (Q17) MPS-A13 2n5875
    Blue drop target bank L18 (Q18) MPS-A13 2n5875
    Hulk Left Shooter Sol.6 (Q31) 2n6043 2n5875
    Right Shooter Sol.7 (Q30) 2n6043 2n5875
    Joker Poker Kings drop target bank L17 (Q17) MPS-A13 2n5875
    Pinball Pool Left drop target bank L17 (Q17) MPS-A13 2n5875
    Roller Disco Left drop target bank Sol.7 (Q30) 2n6043 2n5875
    Torch Left drop target bank Sol.6 (Q31) 2n6043 2n5875
    Asteriod Annie Left drop target bank Sol.7 (Q30) 2n6043 2n5875
    Buck Rogers Vari-Target L17 (Q17) MPS-A13 TIP115

The Gottlieb System 1 CPU controlled solenoid arrangement.
From actual Gottlieb documents, so it's their property, but
modified by me so I guess it's their's and mine.

Transistor Testing Overview.

    After doing the ground modifications on the Driver board, test all the transistors (which control the playfield lamps and solenoids). It only takes a minute, it's real easy, and it prevents problems after the board is installed.

    NOTE 1: testing transistors with a DMM is only about 95% certain to work. The DMM is testing the transistors at "low load", which is unlike how the transistors will ultimately be used in the game! MPS-U45 transistors are particularly prone to testing good, but not working in the game.

    NOTE 2: Any transistor that tests "bad" should also have its playfield coil tested too as outlined here. If the driver board transistor(s) are replaced, but the playfield coil is burnt and has low resistance, it will immediately blow the freshly replaced driver board transistors.

    Testing System1 Transistors with the Driver Board Removed.

      MPS-A13 transistors (driver board locations Q5-Q24, Q33-Q44). The MPS-A13 transistors are used for CPU controlled playfield lights. These transistors test the same in circuit and out of circuit.
      • Using a DMM (Digital Multi-Meter), put the meter on the "Diode" setting.
      • On the COMPONENT side of the board, put the RED lead of the DMM on the middle trace (the base) of the transistor.
      • Put the black DMM lead on the left transistor lead. This should show about 1.3 (emitter - ground).
      • Put the black DMM lead on the right transistor lead. This should show about .7 (collector).
      • Anything within .1 of these values is good.
      • If getting zero or no reading for a test, that transistor is bad.
      • If a reading of .4 to .6 is seen, good chance that transistor is probably bad too.
      • If in doubt, compare the readings of the transistor in question to the other surrounding transistors of the same type. They should all read about the same value.

      MPS-U45 transistors (driver board locations Q1-Q4, Q29).
      The MPS-U45 is used for the tilt and game-over relays (Q2/Q1), and a pre-driver for the 2N3055 transistor (Q29), and the High Game to Date and Shoot Again backbox lights (Q3/Q4). Sometimes Q3 and/or Q4 are used for pre-drivers to under the playfield mounted 2N5875 transistors. The MPS-U45 transistors test the same in circuit and out of circuit.

      • Using a DMM (Digital Multi-Meter), put the meter on the "Diode" setting.
      • On the COMPONENT side of the board, put the RED lead of the DMM on the middle trace (the base) of the transistor.
      • Put the black DMM lead on the left transistor lead. This should show about 1.3 (emitter - ground).
      • Put the black DMM lead on the right transistor lead. This should show about .7 (collector).
      • Anything within .1 of these values is good.
      • If getting zero or no reading for a test, that transistor is bad.
      • If a reading of .4 to .6 is seen, good chance that transistor is probably bad too.
      • If in doubt, compare the readings of the transistor in question to the other surrounding transistors of the same type. They should all read about the same value.

      2N6043 or SE9300 transistors (driver board locations Q30-Q32, Q25-Q28).
      These are used for the sound/chime coils (Q26-Q28), the knocker (Q25), the outhole kicker (Q32), and two other playfield devices (Q30/Q31). This transistor tests the same in circuit and out of circuit.

      • Set the DMM to the "diode" setting.
      • On the COMPONENT side of the board, Put the black lead on the center lead of the 2N6043 or SE9300 transistor, and the red lead on each leg one at a time. A reading of .4 to .6 for each transistor leg should be seen. Anything else and this transistor is bad.
      • The original 2N6043 or SE9300 transistor can be replaced with a TIP102.

      2N3055 transistors (driver board Q45, large transistors with the huge metal case, pre-driven by Q29). This transistor is usually used for a drop target reset bank or other big coil usuage. This transistor tests the same in circuit and out of circuit.

      • Set the DMM to the "diode" setting.
      • Put the black lead on the metal case (or nut/bolt) of the 2N3055, and the red lead on each leg one at a time. A reading of .4 to .6 should be seen for the top leg, and null reading for the bottom leg should be seen.
      • Now put the red lead on the "base" (top) lead of the transistor. Put the black lead on the bottom leg (emitter), and then the metal case of the transistor (collector). A reading of .4 to .6 should be seen with the black lead on the emitter or collector.
      • Any other readings and this transistor is bad and needs replacing (they are about $1 each at Radio Shack).
      • Remember the 2N3055 is pre-driven by a MPS-U45 at Q29. So if the 2N3055 tests bad, also suspect the pre-driver at Q29.
      • Test the BIG 9.1 ohm 1 watt resistor next to the 2n3055. The resistor should test as 9 or 10 ohms in circuit.

      2N5875/2N5879/2N5883 Remote Playfield Mounted Transistors.
      Some system1 games used more then eight controlled solenoids (which was all the driver board allowed.) The first game to do as such was Joker Poker, as there were four drop target banks on the game, yet only three solenoid drivers are available on the driver board. To get around this, a remote mounted 2N5875 transistor (essentially a TIP36) was added under the playfield, which used a MPS-A13 lamp transistor as a pre-driver transistor.

      Some Gottliebs also used the more robust 2n6043 (essentially a TIP102) as a pre-driver too. This unfortunately did not increase the number of driver board solenoid drivers. Yet Gottlieb did this because they felt the MPS-A13 wasn't up to the task of being a pre-driver for a very heavy duty coil (like a large drop target reset coil.)

      Note remoted mounted (under the playfield) transistors are not used in every System1 game. Here's a table of games with these transistor.

Games with Under the Playfield Transistors
Game Coil Designator Pre-Driver PF Driver
Close Encounters Roto Target Sol.7 (Q30) 2n6043 2n5875
Count Down Yellow drop target bank L17 (Q17) MPS-A13 2n5875
Blue drop target bank L18 (Q18) MPS-A13 2n5875
Hulk Left Shooter Sol.6 (Q31) 2n6043 2n5875
Right Shooter Sol.7 (Q30) 2n6043 2n5875
Joker Poker Kings drop target bank L17 (Q17) MPS-A13 2n5875
Pinball Pool Left drop target bank L17 (Q17) MPS-A13 2n5875
Roller Disco Left drop target bank Sol.7 (Q30) 2n6043 2n5875
Torch Left drop target bank Sol.6 (Q31) 2n6043 2n5875
Asteriod Annie Left drop target bank Sol.7 (Q30) 2n6043 2n5875
Buck Rogers Vari-Target L17 (Q17) MPS-A13 TIP115
* Remote mounted TIP-115 (PNP) instead of a 2n5875.
(Alternatively a TIP36 or 2n5875 can be used.)

    Here's the method to test these remote mounted transistors.

    • Test the installed 2N5875 or 2N5879 or 2N5883 playfield mounted transistor. Set the DMM to "diode" setting.
    • If an under-the-playfield mounted transistor, it is best to isolate the 2N5875 from the driver board. This can be done easily by removing the connectors from the driver board to the playfield (or remove the one lead from the transistor that connects to the driver board, see two steps below). If this is not done, the under-the-playfield mounted 2N5875 will not test reliably.
    • Put the red lead on the metal case of the transistor, and put the black lead on each leg one at a time. If the transistor is installed in the game, a reading of .5 for each leg should be seen. If the transistor is not installed, .5 for one leg, and nothing for the other should be seen The values can be from .4 to .6; anything else and the transistor is bad.
    • It's always best to check the wiring on the playfield mounted transistors too. I've seen them mis-installed by previous repair people. With the transistor front facing left, pins right, long part of transistor up, the farthest pin from you (base, white/red/red wire with pull up resistor) is always connected to the driver board. The nearest pin to you (emitter) connects to the NON-banded diode side of the coil. The case (collector) gets the green ground.
    • Important Note: if the pre-driver MPS-U45 transistor on the driver board for the 2N5875 is bad, the 2N5875 could test as bad (even though it is not)! Again if the under-the-playfield 2N5875 is isolated from the driver board, this will not be an issue.
    • Now put the black lead of the DMM on the BASE of the playfield mounted transistor (this is the transistor lead with TWO wires connected). Put the red lead on either the metal transistor case (collector), or the emitter (the other leg). A reading of .4 to .6 should be seen. Change the red lead to the other transistor terminal, and again .4 to .6 should be seen.

An under the playfield 2N5875 transistor.

Schematic on Countdown for its two under-the-playfield 2N5875 transistors.
From actual Gottlieb documents, so it's their property.

    Modification for Remote Mounted Transistors.
    With system80 games Black Hole and later, Gottlieb added a pull up resistor to the circuit for the remote mounted transistors. An added 4.7k ohm resistor tied the base of the remote transistor to 24 volts (coil power), which was mounted right next to the remote transistor under the playfield. This helped prevent a locked on coil in case the driver board lost power. The pull up resistor modification should be added to system1 games that use remote mounted (playfield) 2n5875 transistors.

An under the playfield 2N5875 transistor with pull-up resistor mod.

Remoted mounted transistor circuit with pull up resistor modification.
From actual Gottlieb documents, so it's their property.

Remoted mounted transistor modified with a pull-up resistor on a Joker Poker.

Problems with locked on solenoids? It could be a ground problem!
(See the mandatory ground modifications listed previously in this
document). Also, all the playfield grounds are discrete. They go
to a Molex plug, and then to a central copper grounding strip. If
one Moxlex pin gets resistance in the plug, this can cause a locked
on coil! To fix this, tie all the grounds together at the (playfield
side) connector. Then if one of two Molex pins fail, the path of least
resistance will be taken, and the coil will not lock on. (Electrical
tape was wrapped around this mess after this picture was taken.)

      74175 chip Test and Q1-Q4 Transistor Test.
      The 74175 chip at Z1 is what controls the transistors for the Game-Over relay, Tilt relay and Q3/Q4 (if used to pre-drive an under-the-playfield mounted transistor). The rest of the 74175 chips are used for the CPU controlled lamps. These chips can be easily tested with a DMM set to the diode function and the game off. Best to do this with the driver board removed.
      • On the COMPONENT side of the driver board (game off), put the red lead of the DMM on the 74175 ground pin 8 (pin at the lower left of the chip).
      • Probe pins 2-7 (top left is pin 1) and 10-16 (top right is pin 9) with the black DMM lead. A value of .6 to .7 should be seen. Anything else and likely the 74175 chip is bad.
      • Pin 1 (top left) and pin 16 (top right) will show .3 to .4 on the meter when probed with the black DMM lead.

      The 74175 chip at Z1 can also be used to test the driver board transistors at Q1-Q4 (Q1=Game Over relay, Q2=Tilt relay, Q3/Q4=any under-the-playfield mounted transistors). With the game on, attach an alligator clip to +5 volts (the positive/upper lead of capacitor C1 on the driver board). Then touch the Z1 pins 2,7,10,15 with the other end of the alligator clip. This will tell the transistors Q1-Q4 to activate its relay (or coil or lamp). This is a good test to run if you are unsure if one of the Q1-Q4 transistors is really good. This test of course assumes that the coil/relay being driven is not locked-on.

      7417 chip Test (CPU board locations Z6,Z7).
      The 7417 chips at Z6 (located just above connector J5) and Z7 (to the right of Z6) can also be used to test the connection from the CPU board to the driver board, and to test the transistors at Q25-Q32 (all the CPU controlled coils).

      With the game on, attach an alligator clip to +5 volts (the positive/upper lead of capacitor C16 on the CPU board). Then touch the Z6 pins 1-6 and pins 8-13 (note pin 7=gnd and pin 14=+5). Each pair of pins (for example Z6 pins 1,2) should fire its associated coil when attached to +5 volts. The same thing can be repeated for Z7 pins 1-4 (only). Refer to the above chart to see which Z6/Z7 pins control which driver board transistor/coil. If only one of the two pairs of pins activates the coil, the Z6 or Z7 chip is bad. If neither pin activates a coil, check the CPU to driver board connector and the driver board transistor.

      This test will tell the transistors Q25-Q32 to activate its coil. This test of course assumes that the coil being driven is not locked-on. If this test passes, yet a coil still does not work, then the problem is most likely the U4 spider chip (which sends the signal to Z6/Z7 to fire a coil). Unfortuantely the U4 spider chip is not available, and the CPU board must be replaced with a NiWumpf or Pascal CPU board.

    Can a CPU board Problem cause a Non-Working Coil?
    Yes! Though not as common of a problem as a driver board issue, there is a spider chip U4 (A1753-CE) which can go bad and not make a coil work or make the coil lock-on. If this is the case, sorry but there is no replacement available for this U4 chip. The only choice is to buy a new NiWumpf or Pascal CPU board. If using a NiWumpf board there are also 7406 or 7416 Hex Inverter/buffer chip at U12 and U13 which can fail making a coil not work properly. On these chips check the input signal to the chip, and then the output signal. They should be opposite of each other (it's an inverter).

    Earlier Solenoid Driver Boards on Cleopatra, Sinbad, Joker Poker -
    Missing Diodes Preventing Coil Voltage Damage.

    The first System1 revision of the Driver board as used on Cleopatra, Sinbad, and early Joker Poker games were missing driver transistor isolation diodes. These seven 1N4004 diodes were added to the Driver board during the production run of Joker Poker. If these diodes are not present, and a coil or driver transistor shorts, this can cause serious damage to the CPU board, allowing 24 volts coil power to back-feed to the CPU board, possibly ruining irreplaceable components.

    Because of this, it is a good idea to check which driver board is installed in your game. Even if you have a later System1 game, check for these diodes (as the driver board could have been swapped at some point).

Added diodes CR2-CR5 and CR1,CR6,CR7.
From actual Gottlieb documents, so it's their property.

    The diodes are easy to spot. At the top edge of the Driver board just to the right of the A3J1 connector (going to the CPU board), there should be four diodes (CR2-CR5). There are also three more diodes (CR1,CR6,CR7) installed below Q32 and Q30 just above connector A3J4. If these diodes are not there, you have an earlier Driver board.

Factory added diodes on the Driver board. Early driver boards will
be missing these seven diodes.

    If your Driver board does not have these diodes, there are a few options. Either add the diodes to your old driver board, get a different driver board (Rottendog sells a replacement), or get a new Steve Kulpa CPU to Driver board hardness.) If you want to add the diodes to an old original driver board, you'll need to add seven 1N4004 diodes for transistors Q25-Q28 and Q30-Q32. This can be done a couple of ways. Below are two pictures (thanks to J.Robertson) showing the modification.

Added diodes on the Driver board component side for Q28-Q25.

Or added diodes on the Driver board solder side for Q25-Q28.

    Another easier way to add the diodes is to buy a new CPU to Driver board harness, with the diodes installed into the harness! This is a very cool idea, one that Steve Kulpa came up with. He sells this harness at Big Daddy Enterprises, and it's well worth the expense. Note using this harness with a Gottlieb driver board that has the diodes is fine too. (So always buy this version of the harness!)

Steve Kulpa's CPU to Driver board harness with diodes installed.

    Modifying your Current Harness for Diodes.
    On early system1 games (Joker Poker, Cleopatra, Sinbad) with first generation driver boards (no CR1-CR7 diodes installed), it's a good idea to modifying your current CPU to Driver board harness to add diodes. This will protect your expensive CPU board from coil voltage damage (if something goes wrong.) This modifiction saves you from having to modify the driver board adding diodes, if it's missing the CR1-CR7 diodes. (Note this modified harness can be used with later Driver boards too.)

Modifying an original CPU to Driver board harness with 1n4004 diodes.

    The point here is to add the CR1 to CR7 diodes, which are missing on early driver boards, to the harness. This protects the CPU board without having to do major modifications to the Driver board. If you're already working on this harness, this is a good modification.

Finished modified original CPU to Driver board harness with 1n4004 diodes installed.

Non-CPU Controlled Coils.

    The Gottlieb System1 games also have several non-CPU controlled coils. There isn't a lot to say about these coils, as their repair is easy compared to the CPU controlled variants. On system1 games the pop bumpers, slingshot kickers, flippers, coin door lock out coils are all non-CPU controlled. This means that once the Game Over relay is energized and the Tilt relay is de-energized, all the above coils have power. (Exception: coin door lock out coil which always has power if the game is on.) After a game ends and the Game Over relay turns off, the pop bumpers, slingshots and flippers all turn "off." Likewise if during a game, where the Game Over relay is energized, and the player tilts (thus engaging the Tilt relay), again power to the pop bumpers, slingshots and flippers all turn "off."

The Gottlieb System1 *NON* cpu-controlled coil arrangement.
From actual Gottlieb documents, so it's their property.

    The non-controlled coils are wired very similar to EM games, where the ball closes a playfield switch, which in turn completes powers to the pop bumper or slingshot. On pop bumpers and slingshots, there's a secondary switch which closes when the coil energizes that tells the CPU board to score points for the device. Williams did something similar up to system11a (but pops and slings had some CPU control, where on system1 games, there's no CPU control.)

    If a System1 pop bumper or slingshot "locks on" and stays energized, the reason for this is very simple; the playfield switch which controls the device is stuck closed. If the device does not work at all, start a game and check for power at both lugs of the coil in question. No power at either lug, check the solenoid fuse. Power at one lug and the coil is bad. No power at either lug check the T (Tilt) relay Normally Closed switch and the Q (Game Over) relay Normally Open switch.

    Also if you are working on a system1 machine and have the playfield "up", the Game Over relay can be manually engaged. This should turn on power to the non-CPU controlled coils like the pop bumpers, slingshots and flippers. This is helpful if you are confused about which coils are CPU controlled, and which are not. If you hold in the Game-over relay, only the non-CPU controlled coils (like the flippers, pop bumpers, slingshots) will activate. This is a nice easy test to do when working on non-CPU controlled coils.


3e. Locked-on or Not Working CPU Controlled Feature Lamps

    On Gottlieb system1 games, there are three lamp circuits. Two are not CPU controlled, and those are the GI (general illumination) 6.3 vac lamps used for the playfield and backbox lights. These are #44 or #47 bulbs (though some backbox lamps may be #455 flashers at the discretion of the owner.) There is a fuse for each GI circuit on the bottom panel. Again these are not CPU controlled lamps (though the playfield GI circuit does go through the Tilt relay, which can turn off the GI playfield lights when the game is tilts.)

    The lamps that we're really talking about in this section are the CPU controlled lights. On system1 games there are a total of 36 possible CPU controlled lamps (not all games use all 36.) Again these are #44 or #47 bulbs, but their power is 6 volt DC (not AC), provided to each the lamps in a "daisy chain." Also these lamps are turned on and off by the CPU board through the driver board, which turns the ground on or off for any particular lamp.

Power for the CPU controlled lamps goes through a fuse (lower blue arrow)
and a bridge rectifier (top blue arrow.)

    CPU Controlled Lamp Power.
    Power for the CPU controlled lamps comes from the larger transformer on the bottom panel. Then it goes through a bottom board fuse, and to a bridge rectifier. The bridge converts this power from AC to DC, converting 6 volts AC to about 8 volts DC. (Under load the 8 volts DC ends up at around 6 volts DC, as this voltage is not regulated.) Now the power is "daisy chained" along the playfield, providing each of the CPU controlled lamps with power. (There are also backbox CPU controlled lights too, being Shoot Again and High Score to Date.)

    If none of the CPU controlled lamps are working, chances are good there is no 8 volts DC for the lamps. With the game on, use a DMM set to DC volts and 6 to 8 volts DC should be seen at all the CPU controlled lamp sockets (use the game's metal coin door for ground.) Power should be seen at both lamp socket lugs (if power is only seen at one socket lug, the bulb is bad.)

The Gottlieb System 1 CPU controlled light arrangement.
From actual Gottlieb documents, so it's their property.

    Also keep in mind that the power for all the CPU controlled lamps goes through a Normally Closed switch on the T (Tilt) relay. If the Tilt relay is energized (because the player tilted during game play), there will be no CPU controlled lights. If the switch activator plate on the Tilt relay is knocked off the relay's frame, this can cause the Normally Closed CPU lamp power switch to open, meaning no power for the CPU lights. Also if the driver board Q2 transistor is shorted, this would keep the Tilt relay permanently energized meaning no CPU controlled lights.

    If there is no power at the CPU controlled lamp sockets, check the 8 volt fuse in the bottom cabinet (5 amp slow-blow). If the fuse is good, also check the bridge rectifier closest to the copper ground strap. It is common for this bridge to go open or short (if shorted its fuse will blow immediately at power-on). If the bridge is suspected as bad, replace it with a new MB3502 or MB3504 lugged 35 amp 200 (or 400) volt bridge rectifier. If all the CPU controlled lamps are dim, the bridge is weak and should be replaced with a new lug-lead 35 amp 200 volt (3502) bridge.

    A suspect bridge can be tested. Use a DMM set to diode function and test the bridge:

    • Put the DMM on diode setting.
    • Put the black lead of the DMM on the "+" (positive) terminal of the bridge.
    • Put the red lead of the DMM on either AC bridge terminal. Between .4 and .6 volts should be seen. Switch the red DMM lead to the other AC bridge terminal, and again .4 to .6 volts should be seen.
    • Put the red lead of the DMM on the "-" (negative) terminal of the bridge.
    • Put the black lead of the DMM on either AC bridge terminal. Between .4 and .6 volts should be seen. Switch the black DMM lead to the other AC bridge terminal, and again .4 to .6 volts should be seen.

    Using the Game's Diagnostic Lamp Test.
    One of the worst features of a system1 game are the built in diagnostics. To say they are terrible would be an understate. Diagnostic test #13 really doesn't help much. What it does is turn on ALL the CPU controlled lamps for about 5 seconds. Then they all go off. That's it, lamp test over, and the test doesn't even repeat (it then cyles to testing the coils and then switches.) Also in attract mode before a game starts, system1 games don't cycle the CPU lamps. (This is rather odd, though Bally and Williams games did that too for their first few titles.) So really the best way to test a CPU controlled lamp is to play a game, and trigger that lamp function in the game.

    Bad Lamp - Check Simple Things First (Bulb & Socket.)
    Of course there are a couple assumptions we need to state when checking lamps. First, is the lamp itself good? Sure you can try and look at the filament of the lamp - if broken the lamp is definitely bad. But a better way is to use your DMM set to low ohms or continuity. A good #44 or #47 bulb will show about 4 ohms of resistance. Or just check the bulb in question in one of the game's GI lamp sockets to see if it lights.

    Additionally the lamp sockets in any system1 game are 30+ years old. Lamp sockets do go bad. If you're sure the bulb is good, a twist of the bulb in the socket can often wake up a marginal lamp socket. A single drop of 3-in-1 oil on the fiber gasket of a lamp socket can often help (the oil swells the gasket, forcing the metal pieces together.) Sanding the inside of the socket isn't really a good choice, as the naked metal will quickly tarnish again, as the zinc corrosion resistant plating is worn away. A better approach is to just replace the lamp socket.

    Again remember on the CPU controlled lamp sockets, you can check for power at the socket (with a good bulb installed) using a DMM. Red DMM lead on either lug of the socket, black DMM lead on ground (metal coin door.) You should see 6 volts DC. If you only get 6 volts on one socket lug, the bulb is bad. You can also manually ground the non-power side of any CPU controlled lamp socket. Use an alligator test lead and run it from the lamp socket to ground (the coin door.) The lamp in question should light. If not, the bulb or socket (or socket power) are bad.

    The Driver Board and CPU Controlled Lamps.
    Now that the power to the lamps is established as good, we can move to the driver board. Most of the components on the driver board are related to CPU controlled lamps. The nine 74175 chips (Z1-Z9) and transistors Q3,Q4 (MPS-U45) and Q5-Q24/Q33-Q44 (L5-L36, MPS-A13) control a total of 36 lamps (or 34 lamps and two solenoids). The lamps are controlled in groups of four with a 74175 chip driving four transistors. The MPS-A13 can drive a single lamp, where the MPS-U45 can drive two lamps. In addition, the MPU-U45 can be used as a pre-driver for an under-the-playfield mounted 2N5875 transistor. But since there are only two MPS-U45 transistors available (Q3,Q4) on the driver board, there can only be two under-the-playfield mounted driver transistors. See the Locked-on Coils section for more details about that.

    A single wire goes from each CPU controlled lamp socket back to the driver board, connecting to its related transistor. The driver transistor (MPS-A13 or MPS-U45) switches ground on through the 74175 chip to illuminate its respective lamp. Hence if any of these single wires are manually grounded with the game on, its respective lamp should light. This can be done easily by using an alligator test lead with one end connected to copper ground strip on the game's bottom panel or any metal cabinet frame piece in the backbox or the coin door. Then touch the other end of the test lead to the right-most leg of a MPS-U45 or MPS-A13 transistor (as facing the driver board installed in the backbox). This tests the connection from the driving transistor to the lamp socket (it does not, however, test the transistor). If the lamp does not light when grounding the transistor leg (and the bulb/socket are good), suspect a bad driver board connector or broken wire (or a bad bulb or light socket). Often lightly sanding the driver board's connector "fingers" can fix a non-working lamp. Or the connector pins may need to be replaced (very common).

    Note a good number of non-working lamp problems are related to connectors. If the .156" single sided Molex connectors at the driver board are in poor condition, this, of course, will mean a lamp will not work. Before attempting driver board repair, check all card edge connectors attaching to the driver board, and re-pin the connectors as needed. See the Connector section of this document for help with that.

    If grounding the right leg of any MPS-A13 transistor does light a CPU controlled lamp, but the lamp refused to working in diagnostic or game mode, next test the transistor in question.

The Gottlieb System 1 driver board transistor layout.
From actual Gottlieb documents, so it's their property.

    Testing the Driver Board Transistors and Chips.
    Each lamp is driven by a 74175 chip and a MPS-A13 or MPS-U45 transistor on the driver board. If a 74175 chip totally fails, it causes four lamps to stop working, and those lamps can either stay always on or off (depending on how the 74175 failed). If a driver transistor fails (which happens far more often than a failed chip), it affects only one lamp. A brightly lit lamp is a sign of a failed driver transistor. A non-working lamp is also a sign of a failed driver transistor (assuming the transistor leg grounding trick does light the lamp). Note the MPS-A13 transistors damage easily if the 8 volts driving the lamp gets shorted directly to its grounding wire with no load (no bulb), usually by a bad lamp or bad lamp socket.

    MPS-A13 Transistor Test (driver board locations Q5-Q24, Q33-Q44).
    For a non-working lamp (that has a good bulb/socket and connector), test the MPU-A13 driving transistor first. The MPS-A13 transistors are used for CPU controlled playfield lights. These transistors test the same in circuit and out of circuit. Best to do this with the driver board removed.

    • Using a DMM (Digital Multi-Meter), put the meter on the "Diode" setting.
    • On the COMPONENT side of the board, put the RED lead of the DMM on the middle trace (the base) of the transistor.
    • Put the black DMM lead on the left transistor lead. This should show about 1.3 (emitter - ground).
    • Put the black DMM lead on the right transistor lead. This should show about .7 (collector).
    • Anything within .1 of these values is good.
    • If getting zero or no reading for a test, that transistor is bad.
    • If a reading of .4 to .6 is seen, good chance that transistor is probably bad too.
    • If in doubt, compare the readings of the transistor in question to the other surrounding transistors of the same type. They should all read about the same value.

    MPS-U45 Transistor Test (driver board locations Q1-Q4, Q29).
    The MPS-U45 is used for the tilt and game-over relays (Q2/Q1), and a pre-driver for the 2N3055 transistor (Q29), and the High Game to Date and Shoot Again backbox lights (Q3/Q4). Sometimes Q3 and/or Q4 are used for pre-drivers to under the playfield mounted 2N5875 transistors. The MPS-U45 transistors test the same in circuit and out of circuit. Best to do this test with the driver board removed.

    • Using a DMM (Digital Multi-Meter), put the meter on the "Diode" setting.
    • On the COMPONENT side of the board, put the RED lead of the DMM on the middle trace (the base) of the transistor.
    • Put the black DMM lead on the left transistor lead. This should show about 1.3 (emitter - ground).
    • Put the black DMM lead on the right transistor lead. This should show about .7 (collector).
    • Anything within .1 of these values is good.
    • If getting zero or no reading for a test, that transistor is bad.
    • If a reading of .4 to .6 is seen, good chance that transistor is probably bad too.
    • If in doubt, compare the readings of the transistor in question to the other surrounding transistors of the same type. They should all read about the same value.

    74175 Chip Test (driver board locations Z1-Z9).
    The 74175 chips is what controls the lamp (and solenoid) transistors, with each 74175 chip on the driver board controls four lamps. The 74175 chips can be easily tested with a DMM set to the diode function. Best to do this with the driver board removed.

    • On the COMPONENT side of the driver board (game off), put the red lead of the DMM on the 74175 ground pin 8 (pin at the lower left of the chip).
    • Probe pins 2-7 (top left is pin 1) and 10-16 (top right is pin 9) with the black DMM lead. A value of .6 to .7 should be seen. Anything else and likely the 74175 chip is bad.
    • Pin 1 (top left) and pin 9 (top right) will show .3 to .4 on the meter when probed with the black DMM lead.

Lamp Signal
(CPU encoded
at U3)
CPU Decoder
74154
CPU Inverter
7404
CPU Connector Driver
Connector
Driver
74175
Driver
Transistor
Lamp # Driver
Connector
to Lamp
DS1 z30 pin 2 z24 pin 1,2 a1J5 pin 21 a3J1 pin 5 z1 Q1-Q4 L1-L4 J5 pin18,19,17,15
DS2 z30 pin 3 z24 pin 3,4 a1J5 pin 20 a3J1 pin 6 z2 Q5-Q8 L5-L8 J5 pin13,14,12,11
DS3 z30 pin 4 z24 pin 5,6 a1J5 pin 19 a3J1 pin 7 z3 Q9-Q12 L9-L12 J5 pin9,10,8,7
DS4 z30 pin 5 z24 pin 13,12 a1J5 pin 18 a3J1 pin 10 z4 Q13-Q16 L13-L16 J5 pin5,6,4,3
DS5 z30 pin 6 z24 pin 11,10 a1J5 pin 17 a3J1 pin 13 z5 Q17-Q20 L17-L20 J5 pin1,2
J3 pin20,18
DS6 z30 pin 7 z25 pin 1,2 a1J5 pin 16 a3J1 pin 14 z6 Q21-Q24 L21-L24 J3 pin16,17,15,14
DS7 z30 pin 8 z25 pin 13,12 a1J5 pin 14 a3J1 pin 15 z7 Q33-Q36 L25-L28 J3 pin12,13,11,9
DS8 z30 pin 9 z25 pin 3,4 a1J5 pin 15 a3J1 pin 16 z8 Q37-Q40 L29-L32 J3 pin7,8,6,5
DS9 z30 pin 10 z25 pin 11,10 a1J5 pin 13 a3J1 pin 17 z9 Q41-Q44 L33-L36 J3 pin4,3,2,1

    How do I know which Transistor Controls Which Lamp?
    If the schematics are not available, the easiest way to do this is by lamp socket wire color. For a failed lamp, look at the wire color that connects to its lamp socket, and make a note of it.

    With the game powered off, go to the driver board and examine the connectors along the bottom edge of the driver board. Find the wire color in question and make note of the connector and pin. Using a DMM set to continuity, put one lead of the DMM on the pin with the correct wire color. Then probe the RIGHT leg of each transistor on the driver board. When a continuity buzz is heard, the transistor controlling the lamp in question has been found.

    To double check you have found the correct transistor, power the game on. Now use an alligator test lead and connect one end to ground. Momentarily touch the other end of the alligator test lead to the RIGHT leg of the transistor. The CPU controlled lamp should light.

    Four Lamps Don't Work.
    From the table above you can see that any 74175 chip on the driver board controls four lamps. It's easy to suspect one of the 74175 chips as bad, but that's usually not the case in my experience. A far bigger thing to suspect is the connector coming from the bottom edge of the CPU board to the top edge of the driver board. Battery corrosion and age often takes its toll on these connectors, and the lamp signal gets lost from from the CPU board's spider chip to the 74175 driver board chip. Also on the CPU board the z24 or z25 (7404) inverter chip likes to die too.

    Summary of CPU controlled Lamps.
    For a non-working lamp, always start with checking power at the socket and if the bulb/socket itself are good. Then work up the chain to the driver board transistor, grounding it's right leg to see if the lamp goes on. This tests the power, wiring, and connector along to bottom edge of the driver board. Now the transistor itself can be tested, and potentially the 74175 chip that controls it. Next suspect the connector between the driver board and CPU board. Then on the CPU board look at the 7404 inverter chips at z24/z25. Next is the 74154 decoder chip at z30 - this gets the encoded signal from the spider chip U3. Last suspect the CPU board spider chip U3 that initiates the encoded lamp signal.

    Semi-CPU Controlled Lamps.
    There are two backbox lamps that are what I call "Semi-CPU controlled". That is the Game-Over lamp and the Tilt lamps. Both of these lamps run on 6.3 volts AC (the General Illumination power), but they are not GI lamps.

    The 6.3 volts AC power for the Tilt lamp goes through a Normally Open switch on the Tilt relay. The Tilt relay is then controlled by the CPU board. If during game mode the machine is tilted, the Tilt relay energizes and stays energized until the current ball drains. While the Tilt relay is energized, this closes the switch to the Tilt lamp, turning the Tilt lamp on. Hence the semi-CPU control of the Tilt lamp.

    The Game-Over lamp works in a similar manner. The 6.3 volts AC for the Game-Over lamp goes through a Normally Closed switch on the Game-Over relay. The Game-Over relay is controlled by the CPU board. When a game is started, the Game-Over relay energizes for the duration of the game (enabling power to the flippers, etc.) This opens the Game-Over lamp switch, turning the Game-Over lamp off while a game is played. Hence the semi-CPU control of the Game-Over lamp.


3f. Switches and the Switch Matrix

    There's two kinds of switches in any system1 game. High power (tungsten contact) switches at carry 24 volts, and low power (gold flashed) switch matrix switches that carry 5 volts. We'll be talking mostly about the switch matrix switches. High power switches (like flipper EOS, flipper cabinet, pop bumper activation, sling shot activation switches and some relay switches) are all high power tungsten contact which carry 24 volts DC. The larger contacts allow the EMF (electromotive force) to arc and not burn the contacts. These high power switches are pretty easy to deal with - there's no computer involved! You can actually file these switches too. Now the gold flashed switch matrix switch you can't file, so please don't try! You will ruin the switch contacts if you do, causing more problems than you're solving.

Low power gold flashed inlane/outlane switches. These are part of the
switch matrix, and should *never* be filed. Note the lack of diodes mounted
on these switches - they do in fact have diodes, just Gottlieb didn't mount
the diodes directly on the switches themselves.

    The Switch Matrix.
    The way the computer talks to the playfield is via switches. Not just any switches, but low power (5 volt), gold flashed switches. So the computer can "scan" switches quickly to see which are opened or closed, the switches are organized into a "matrix" (no not the movie.) Being in a matrix allows the CPU to quickly see what switches are open or closed, many times a second. This is needed as things happen fast on that pinball playfield.

    The System1 switch matrix consists of five strobe lines (Strobe0 to Strobe4) and eight return lines (Return0 to Return7). This makes for a total of 5x8 or 40 switches in any System1 game. The switches are numbers as such: 00-04, 10-14, 20-24, 30-34, 40-44, 50-54, 60-64, 70-74. The computer can scan the strobe lines and look for a closure through the return lines. If a strobe is seen through a return, the cross of those two lines indicates an individual switch closure.

    The first five switches (return line #0, switch numbers 00 to 04) are consistent in all system1 games:

    • 00 = test/play button
    • 01 = coin chute #1
    • 02 = coin chute #2
    • 03 = credit (start) button
    • 04 = tilt

    Outside of the switch matrix, there are three common switches used in all System1 games. These three switches are not part of the switch matrix. This includes two slam switches and the outhole switch. All system1 games have two slam switches - the first is a weighted Normally Closed (NC) switch on the coin door. The second slam switch is also a Normally Closed switch, located at the end of the ball roll tilt cage. The two slam switches and the outhole switch do NOT have a switch matrix number designations. More info on these switches is in a section below...

Switch matrix table from a Joker Poker.
This document is from the Joker Poker manual, so it belongs to Gottlieb.

    All Switch Matrix Switches Have Diodes.
    Because of the scanning of the strobe and return lines in the switch matrix, diodes (one way applicators) are used so there's no "cross talk" between switches. If there were no diodes on the switches, a single switch closure would make the computer think all switches on that strobe line were closed.

    Gottlieb implemented switch diodes a bit differently than other companies. Nearly all other pinball makers mounted diodes directly on the switches themselves. Gottlieb however didn't do that - they mounted the switch diodes on small bakelite insulator boards under the playfield and away from the actual switches involved. This left less confusion when hooking up a new switch (how is the diode wired to the switch?), but created more confusion if you were used to working on other makers' games. Gottlieb also used 1n270 switch diodes opposed to 1n4001 diodes like other makers.

Switch diode boards as used on a Joker Poker, mounted under the playfield.

    Switches Outside the Switch Matrix - Slam & Outhole.
    There are additional switches that are consistent on every System1 game, and that are outside of the switch matrix. These are the two slam switches (CPU A1J6 pin 2) and the Outhole switch (CPU A1J7 pin 1.) These switches are activated by touching them to ground. In the case of the Slam switches, they should be permanently tied to ground or the game won't play or boot - the score displays will just "strobe" very fast immediately upon power on (no five second bootup delay). If either Slam switch is opened (disconnected from ground) during attact mode or game play, again the score displays will "strobe" very fast and the game will lock up until the slam switches are closed.

    All system1 games have two slam switches - the first is a weighted Normally Closed (NC) switch on the coin door. The second slam switch is also a Normally Closed switch, located at the end of the ball roll tilt cage. The two slam switches and the outhole switch do NOT have a switch matrix number designations.

    On the Ni-Wumpf board, there is no slam switch (it was completely removed from the circuit because of the problems it causes with stock Gottlieb System1 CPU boards). Also the Outhole switch is shown on the Ni-Wumpf switch test as switch number 15 (which is clearly outside of the 10-14 return1 row of switches). On the Gottlieb System1 switch test the outhole switch is shown as switch number 12 (which is clearly is not, but that's how the test shows it).

    Coin Door Switches - a Common Switch Matrix Problem.
    Because system1 games do not have a free-play setting, users often press the coin switches inside the coin door with their fingers to add credits. This is fine, but while doing this often the user will move the "lock-out wire" so it touches one of the coin switch blades. This will short that return/strobe switch matrix line to ground, making the game freak-out. Usually a game won't start, or there will be some other strange game behavior. The game may not even boot, or may act like it is always tilted or slam tilted.

Coindoor lock-out wire shorting against a coin switch (blue arrow.)
The red arrow shows how the insulating fish paper is mis-placed. Note the
coin mech has been removed to show this issue.

    So first thing before doing any switch matrix board work, check the two coin switches and make sure the lock-out wire is not touching the metal coin switch blades. Insulating "fish paper" is used by the factory to help prevent this problem.

    Common Switch Problems (the Easy Stuff.)
    Two common switch matrix problems are dirty switch contacts and mis-adjusted switch blades.

      Cleaning Dirty Switches.
      When a switch doesn't work, the best first step is to clean the switch contacts. Why do they get dirty? See all that black dust under the playfield? That gets on the switch contacts. With gold flashed switch matrix switches, use some alcohol (90%) and a small rag. Then wipe off dirt from switch contacts with the alcohol wet rag. Or you can take a business card, and run it between the switch blades (cleaning the contacts), with the blades manually closed. Another trick is to wet the business card with alcohol, and run it between the switch contacts (this will clean the contacts better than a dry business card.) Again, remember, do NOT file gold flashed switch matrix contacts!

      The other problem that comes up a lot are mis-adjusted switches. Either the gap is too large between the two switch blade contacts, or the two contacts are too close or even permenantly closed. (A permenantely closed switch will be ignored by the switch matrix.) Switch blades should be bent so there's a 1/16" to 1/8" gap between the contacts. Too close and vibration will close the switch, too wide and the switch may never close.

      Mis-Adjusted Switches.
      Note you can easily mis-bend switch blades. One of the switch blades will have a dampner. This is easy to mis-bend, shorting the two switch contacts together. (See picture below.) Obviously you don't want to do that.

      Another common problem with mis-adjusted switches occurs after new playfield rubber has been installed. New rubber has different tension, and can pull blades together more than old rubber, permenantly closing the switch. This is really a problem on non-computer controlled slingshots, where the sling shots can "machine gun" or even lock-on if the contacts are too close. A problem with CPU controlled switches too, but mostly because it messes up the scoring (and generally doesn't lock on anything.)

Here's a mis-adjusted Gottlieb switch blade pair, where the
dampening blade is shorting the two contact blades together.
Obviously this is a bad thing.

      Dirty Switches, Random Scoring, and NiWumpf MPU Board.
      One problem with the new replacement NiWumpf MPU board is random scoring. This happens on games with drop targets. When the targets are down, the drop target associated with each switch is closed. As the game vibrates, a dirty closed drop target switch can quickly toggle open and then closed, due to crud on the switch contacts. This is known as switch bounce.

      On a stock Gottlieb system1 MPU board this switch bounce isn't a problem - the CPU isn't fast enough to "see" a dirty switch bounce open and closed. Yet on a NiWumpf board, the CPU is fast enough to see switch bounce. To help diagnose this problem, NiWumpf has a switch test diagnostic option. In this test, the player3 display shows the current switch just closed (with no sound as the switch closes.) If the NiWumpf sees switch bounce, it displays a message in the player1 and player2 displays saying "clean switch", and sounds the 10 point sound. So if in the NiWumpf switch test you hear a sound when a switch is closed, the NiWumpf thinks that switch is dirty.

Joker Poker with a NiWumpf MPU board installed and in switch test.
Note the message "clean switch", indicating a dirty switch causing switch bounce.
This can be a problem on games with drop targets, causing random scoring.

      To fix this problem use a rag wet with alcohol and clean the switch contacts. (Never use a file, as these are gold flashed contacts.) This should fix the "clean switch" error. This should resolve any random scoring happening in a system1 game with a NiWumpf MPU board.

    CPU Board Switch Matrix Plugs.
    If a switch doesn't work, yet it is clean and adjusted properly, another common problem is the switch connector on the CPU board. There are two plugs responsible for the switch matrix on the CPU board. They are both directly below the battery, so often these two plugs need to be re-pinned (due to battery corrosion) for the game to work properly. This is a HUGE problem on system1 games. It's not uncommon to re-pin all the switch matrix CPU plugs on a system1 game due to corrosion and wear and tear.

The two switch matrix plugs on the CPU board, right below the battery.

      Plug A1J6.
      This plug is used for the coin door switches like the all important Slam switch and the coin, credit, tilt, and test switches.
      • J6 pin 1 (grn/yel) - ground
      • J6 pin 2 (org/blk/blk) - slam switch
      • J6 pin 3 (blk/blu/blu) - return 0
      • J6 pin 4 (blk/red/red) - strobe 1
      • J6 pin 5 (blk/org/org) - strobe 2
      • J6 pin 6 (blk/yel/yel) - strobe 3
      • J6 pin 7 - not used
      • J6 pin 8 (blk/brn/brn) - strobe 0
      • J6 pin 9 - not used

      Plug A1J7.
      This plug is used for the playfield's entire switch matrix.

      • J7 pin 1 (gry/org/org) - outhole switch
      • J7 pin 2 (blk/brn/brn) - strobe 0
      • J7 pin 3 (blk/red/red) - strobe 1
      • J7 pin 4 (blk/org/org) - strobe 2
      • J7 pin 5 - not used
      • J7 pin 6 (blk/grn/grn) - strobe 4
      • J7 pin 7 (blk/yel/yel) - strobe 3
      • J7 pin 8 (grn/yel) - ground
      • J7 pin 9 - not used
      • J7 pin 10 (org/blu/blu) - return 7
      • J7 pin 11 (brn/blu/blu) - return 6
      • J7 pin 12 (blk/blu/blu) - return 0
      • J7 pin 13 (brn/blk/blk) - return 1
      • J7 pin 14 (brn/red/red) - return 2
      • J7 pin 15 (brn/grn/grn) - return 5
      • J7 pin 16 (brn/yel/yel) - return 4
      • J7 pin 17 (brn/org/org) - return 3

System1 Switch Matrix
  Strobe 0
Blue 011
Strobe 1
Org 022
Strobe 2
Brn 033
Strobe 3
Grn 044
Strobe 4
Purp 055
Return 0
Yel 066
Sw #00
Test
Sw #01
Coin1
Sw #02
Coin2
Sw #03
Start
Sw #04
Tilt
Return 1
Blue/Wht 100
Sw #10 Sw #11 Sw #12 Sw #13 Sw #14
Return 2
Org/Wht 122
Sw #20 Sw #21 Sw #22 Sw #23 Sw #24
Return 3
Brn/Wht 133
Sw #30 Sw #31 Sw #32 Sw #33 Sw #34
Return 4
Grn/Wht 144
Sw #40 Sw #41 Sw #42 Sw #43 Sw #44
Return 5
Purp/Wht 155
Sw #50 Sw #51 Sw #52 Sw #53 Sw #54
Return 6
Yel/Wht 166
Sw #60 Sw #61 Sw #62 Sw #63 Sw #64
Return 7
Yel/Blk 366
Sw #70 Sw #71 Sw #72 Sw #73 Sw #74

Switch matrix from Charlies Angles. Note how Gottlieb docuements their
switch matrix reverse of other manufacturers. Usually the returns are rows,
and the strobes are columns. For some reason Gottlieb reverses this in
their drawings. This picture is from Gottlieb documents and is their property.

      Remember the coin door switches (or any playfield switch) also do not have their diodes mounted on the switches. Like the playfield switches, the coin door switch diodes are mounted elsewhere. In this case, the coin door switch diodes are on the bottom panel next to the ground plane and auxiliary power plug.

The coin door switch diodes, mounted on the bottom board.

    Shorting GI or Solenoid Voltage to the Switch Matrix.
    One very big problem with Gottlieb system1 games is if somehow the solenoid voltage (24 volts DC) or General Illumination voltage (6.3 volts AC) is shorted to the switch matrix. This can happen if someone is poking around inside a powered-on game with a screwdriver. Or it could happen because of a mis-installed coil, or even a switch wire breaks and somehow shorts to coil or GI voltage.

    If any of these scenarios happen, a couple things can happen. Almost certainly the 7404 chip at Z8 (the strobe0-strobe4 buffer chip) can fail. Also the 7405 chip at Z9 (return0-return5 buffer) and Z28 (return6-return7 buffer) can also fail. This is not a huge deal as these chips are readily available. But behind the 7404/7405 chips is the irreplacable U5 (A1752CX) spider chip. If this chip fails, the CPU board is junk and cannot be fixed, because this spider chip is no longer available and impossible to find.

    J.Robertson is currently testing a modification to the CPU board to prevent the over voltage getting to the irreplaceable U5 spider. He has added clamping 1N4004 diodes to the circuit. These can be placed across the resistors R65-R72 with the band of the diode soldered to the +5VDC end of the resistor, and the non-banded end to the other side of the resistor. Then on resistors R57-R62, connect the non-banded end of the diodes to the junction of the resistor and the trace leading to the IC, and the banded end to a convenient +5 volt point.

J.Robertson's System1 CPU modification to protect the U5 spider chip from over-voltage.

    The idea is that there are a pair of 1N4005 diodes on each strobe and return line. This should prevent the return/strobe lines from going above +5 volts, thus protect the U5 spider chip from the 24 volt DC solenoid bus or the 6.3 volt AC GI power.

    Using the Diagnostic Test for the Switches.
    Again, as with the lamp test, diagnostic test #13 can be used to test switches. Don't sit down when doing this, this test goes fast! First the lamps are tested for 5 seconds, then the eight CPU controlled coils/sounds. Last the switch test. If no switch is seen "tested" within 5 seconds, the game goes back to attract mode. (Not a very friendly test.) This is also the slowest switch test I've ever seen, as the reaction time from switch closure to the switch number displaying on the credit/ball display is slooow.

    One advantage to the diagnostic test #13 for switches is if there's a short in the switch matrix. This test will show for example all the switch in a particular strobe or row that are shorted, in lowest to highest order. Like if strobe #1 is shorted, switches #1,11,21,31,41,51,61,71 will all show in the switch test. The other switch tests described below won't give this information. So for certain situations, test #13 is worth the trouble.

    Before starting the switch test, it's best to have all the drop targets "up", so all the playfield switches are "open." The ball can stay in the outhole, as technically it's not part of the switch matrix (though it does show up in the test as switch #12.) Because of this, it's best to remove the ball from the game to avoid any confusion. After the lamp and coil tests are done, quickly test the switch you want to test. The switch number should show up on the credit/ball display.

    Personally I find the best way to test system1 switches is in game mode. This version of "switch test" is far easier, less stressful, and quicker.

    Another Version of the Switch Test (Switch Display Ficker Test.)
    For some strange reason, when a system1 games is in attract mode, and a switch matrix switch is closed, the score displays "flicker" for just a moment. Until you have seen it, it's hard to explain, but these system1 games do it. It's an extremely fast flicker, so the score displays have to be in good shape and bright to see it. But instead of using diagnostic test #13 or starting a game, this is another alternative way to test switches. (Though personally I find testing switches in game mode far easier as there's both visual and sound verification of a switch closure.)

    The one advantage to the attract mode flicker switch test is that parallel switches can often be seen in this mode. For example, 10 point switches. Often there are multiple 10 point switches on a game (behind the drop targets, redundant sling shot switch, bouncing rubber switch, etc.) If one of these parallel 10 points switches are permanently closed, NONE of the other 10 points switches will work during game play. But using the attract mode flicker switch test, often a parallel switch closure can be seen.

    Switch Matrix Problems.
    If the switch matrix is not working correctly, the best approach is to use a logic probe to check the return and strobe lines. First with the game off, defeat the Slam switch right on the CPU board (if you have not done that already). Then turn the game on and let it boot. Now remove CPU switch connectors J6 and J7. Now take a logic probe and check the following chip pin number for the appropriate activity. Note the first pin number listed below connects to the U5 spider chip, and the second pin number goes to the board connector.

    Z8 - 7404 (switch Strobes):
    This is the chip that fails most often (more so than the return line chips).

    • Z8 pin 1/2 = Strobe0: both pins pulsing.
    • Z8 pin 3/4 = Strobe1: both pins pulsing.
    • Z8 pin 5/6 = Strobe2: both pins pulsing.
    • Z8 pin 9/8 = Strobe3: both pins pulsing.
    • Z8 pin 11/10 = Strobe4: both pins pulsing.
    • Z8 pin 13/12 = Strobe5: both pins pulsing (not used in any system1 games).

    If the logic probe shows pulsing just on the input side of the 7404 (first pin listed above) and not on the output pin, then the 7404 chip at Z8 is bad. If incorrect activity (no pulsing) is seen on the input side of the 7404 chip, then the U5 spider chip is bad.

    Z9/Z28 - 7405 (switch Returns):

    • Z9 pin 2/1 = Return0: both pins high.
    • Z9 pin 4/3 = Return1: both pins high.
    • Z9 pin 6/5 = Return2: both pins high.
    • Z9 pin 8/9 = Return3: both pins high.
    • Z9 pin 10/11 = Return4: both pins high.
    • Z9 pin 12/13 = Return5: both pins high.

    • Z28 pin 4/3 = Return6: both pins high.
    • Z28 pin 10/11 = Return7: both pins high.


3g. Score Display Problems and Fixes

    Warning! Do not remove or attach CPU connectors J2 and J3 (the right side score display connectors) with the game power on. Do not remove a score display with the game power on. Doing either of these with the power on will likely damage the CPU board score display driver chips, usually Z16-Z17 (digit control) and/or Z13-Z15 (ones control) and/or Z18-Z21 (digit selection). Sometimes the score display's UDN6116 chip blows too. Also be aware that the score displays run at higher voltages (60 volts.) So just keep that in mind and don't shock yourself.

    Potential Display Problems.
    There's only about three things that can be wrong with non-working score displays: No power (power supply problem), bad score display glass and/or board, and/or bad CPU data going to the displays.

    Is there Score Display Power?
    If none of the score displays work, the first course of action is to test the display power. Power comes to the power supply A2 board, which develops all the voltages for the score displays from the bottom board AC power. There's a 1/4 amp 69 volt fuse (right most fuse) on the bottom board. If that's blown, obviously there won't be any power to the score display. DO NOT over fuse! It's 1/4 amp for a reason. If you over fuse this, and a score display or power supply has a short, it can ruin the main power transformer.

    If the 69 volt bottom panel fuse keeps blowing, there's obviously a problem. To diagnose this first remove the right side J3 power supply connector. Power up with a good bottom board 1/4 amp fuse. If the fuse still blows, the problem is on the power supply board. Diodes CR6-CR9 (1n4004) often short, and can immediately blow the 1/4 bottom board fuse. These are easy to test with a DMM set to diode function (should see .4 to .6 volts.)

    If the bottom board 1/4 amp fuse is not blowing, next check the power output at connector J3 with a DMM. Remember the ground connection for the 60/42 volt score display power is different than the other grounds. So you must use power supply connector J3 pin 5 as your ground reference when measuring 42 or 60 volts. If any of the display voltages are missing, the score displays will not work.

    • A2 J3 pin 1 = 60 vdc (top most pin)
    • A2 J3 pin 3 = 42 vdc
    • A2 J3 pin 5 = Ground (common)
    • A2 J3 pin 7 = 4 vdc
    • A2 J3 pin 8 = 8 vdc

    The 60 volts is used for the larger 6 digit display main power, along with the 8 volt "reference" voltage. The credit/status display uses 42 volts for it's main power, and 4 volts as its "reference" voltage. This is all suppled by the power supply connector J3, so check the voltages there using J3 pin 5 as ground. The 60vdc and 42vdc power lines come from the 69vac bottom board voltage. The 4vdc and 8vdc reference voltages come from the 11.5 vac supplied by the bottom board.

    Once you have verified that the power supply is working, turn off the game and re-connect the J3 power supply connector. Power back up and check the voltages again. They should be about the same. Note there is a pot to adjust the 60 volts on the original Gottlieb power supply. (You can "dial in" that voltage if you so desire.) If the score displays still don't work (and the CPU board is booting), then there could be a CPU data problem, or bad displays themselves.

    Bad Score Display Glass and/or Display Board Chips.
    It happens, score display glass does go bad. If you see white corners on the glass, chances are good that the display glass is bad. Below is a picture of a bad system1 score display. Notice the white corners. Also if you look close at the (clickable) larger version of this picture, you can see some of the filament wires are broken! This glass display tube is junk, and there's no repairing it. Also if the "nipple" on the back of the display glass if broken, the display is also unrepairable.

A bad system1 or system80 score display glass with white corners and
a broken filament wire (which can be seen if you look closely.)

    Bad display glass boards shouldn't be discarded though, as the chips on these may still be good. It's best to save the broken display, because you may need the udn6116 or 7432 (status score display) chips later for another repair.

    Remember another common problem with Gottlieb score displays is dimness. Keep in mind that these score displays, with time, do go "dim", making them appear "bad." If the corners of the display glass are black, yet the display doesn't work, it's probably a good time to "recharge" the display as described here. What happens is the display anodes oxidize. If a display hasn't been on for years, often at first the display will show as "dead" or show very dim. Leaving the game "on" for a bit often fixes this problem. Or you can "recharge" the displays (see below for details on that.)

    Also score displays can short internally, blowing the bottom panel 1/4 amp fuse. For this reason, when booting a game that has been sitting for a long time, it's best to turn the game on with just ONE score display connected (player1.) If the game comes up with that display, power off, and connect another display, and power back on. Repeat this until all the score display are connected. This will tell you if any one particular display is a problem.

    The display board also has und6116 chips, which can be tested. These chips handle the display digits. If the chip goes completely dead, the display won't work at all. If if portions of the udn6116 goes bad, certain digits won't work. These chips can be tested though. With the power off, disconnect the display and use a DMM set to diode function:

    • Red DMM lead on udn6116 chip ground (pin 9)
    • Black DMM lead on udn6116 pin 2 to pin 8 - reading of .5 to .7 should be seen.
    • Black DMM lead on udn6116 pin 11 to pin 17 - a null (no reading) should be seen.

    Display Data Introduction and What Controls What.
    Gottlieb System1 (and System80) blue displays are made by Futaba, and are a low-voltage (60 volt) score display. Yea I know 60 volts doesn't sound that low, but compared to the orange 100 volt plasma displays used by Williams and Bally, the Futaba displays are low voltage. Because the Futabas are low voltage, they tend to last longer than the high voltage plasma displays.

    The displays are controlled by CPU spider chip U6 and a few TTL chips. The 7-segment decoders Z16,Z17 (7448) control the digits for the displays. If the displayed numbers look strange then one of these chips is probably bad. Chip Z16 controls player 1/2 displays and the credit/ball display, while Z17 handles player 3/4 displays.

    There is also a circuit that makes number "1" to be shown with an extra eighth segment in the middle of the digit instead of the usual two right side segments. This is done with chips Z13/Z14/Z15 on the CPU board. Suspect those if there are problems in showing number "1".

    The displays are multiplexed, meaning one digit is displayed at a time. This digit selection signals come from CPU chips Z18-Z21.

    Finally there is a UDN6116 chip on the display board itself that controls the digits on the score display.

    System1 and System80 Six Digit Displays Interchangable.
    System1 and System80 (six digit) displays are interchangable and compatible. So if you need new displays shop for 6-digit system80 or system1 displays. The only difference is on system1 display they have a "nipple protector" on the back of the board which went away for system80.

The Gottlieb System 1 CPU controlled light arrangement.
From actual Gottlieb documents, so it's their property.

The 6-digit Futaba score display and 4-digit credit/ball display.

    Recharging System1/System80 Score Displays.
    The six digit blue Futaba score displays used on System1 and System80 games are identical and interchangable. But often the displays will fade over time, eventually not working at all. There may not be any problems with the display circuits themselves, but instead there may be oxidation on the display glass filament wires. There is a trick to burn this oxidation off the filament wires, making the displays work like brand new (there is a limited number of times you can do this though, the law of diminishing returns does apply).

System1 or system80 six digit score display being "recharged" with 24 volts DC.

    First turn the game off and remove one of the 6-digit score displays. Then take a pair of jumper wires, and connect them to the front door coin lock-out coil lugs (24 volts DC). Next attach the alligator clips to the outside most pins of the score display (it does not matter which gets ground). Now turn the game on for 3 to 5 seconds, then immediately turn the game off. While the game is on, the thin horizontal filament wires in the score display glass will glow. This burns the oxidation off the filament wires.

      WARNING: Do not leave the power to the display for more than 5 seconds, or you could burn a filament wire ruining the display! Also do not use coil voltage to recharge the 4-digit ball/credit display. If you need to recharge a 4-digit ball/credit display, use 8 to 12 volts DC instead. I have even heard of some people using a 9 volt battery to do this.

    Two Different 6 Digit Display Driver Chips.
    The Gottlieb system1 (and system80) display glass boards can have two different sets of driver chips. The most common variant uses two udn6116 high voltage display driver chips. There is also another variant that uses two Dionics DI513 chips. If you have a choice, go with the udn6116 variant, as the 6116 chips are available (though expensive.) The Dionics DI513 chips are really hard to find, making this type of score display board harder to repair.

Top: a bad system1 display glass using the Dionics DI513 chip set.
Bottom: a good system1 display glass using the more common udn6116 chips.
Note the corners of these two glasses - the bottom glass had black corners
(which is good), and the top bad glass had white corners (which is bad,
this glass is junk.)

    Protect the Nipples.
    System1 and system80 score glasses have "nipples" on the back side of the display glass. If this nipple breaks, the glass is useless (there's no repairing this.) Most system1 games have a black plastic cover protecting the nipple from breakage. But later system1 and system80 games are missing this cover. If you're generally an protective person, it's not a bad idea to protect the glass nipples. I use a nylon wire bundle tie, put it over the nipple, and fill the area with silicon. This way if the display is mis-handled, chances are good the nipple won't break.

A system1 or system80 display glass with an unprotected nipple.

A system1 or system80 display glass with a modified and protected nipple.


3h. DIP switch settings.

    There are three banks of eight DIP switches on the CPU board. They are used to set game pricing and other game parameters. These switches are consistent for all system1 games.

    The first eight switches control play pricing. There are four switches for each coin slot, so that the switches 1-4 control left side and switches 5-8 the right side coin slot. The other two DIP switch banks control game options.

    My suggestion is to set the CPU board DIP switch as follows to make repairing the game easier. After you have the game working, set the switches as desired.

    • DIP 1-8=all off (one coin, one credit). Another common setting is to make switches 1=on (and sw 2-8=off) for 1 coin 9 credits.
    • DIP 9=on (three balls/game, off=5 balls/game).
    • DIP 10=on (match feature on).
    • DIP 11=on (replay instead of extra ball, off=extra ball).
    • DIP 12=on (tilt kills current ball only, off=tilt kills game).
    • DIP 13=on (show number of credits).
    • DIP 14=on (play a tune when game started).
    • DIP 15,16 not used.
    • DIP 17,18=on (maximum credits 15).
    • DIP 19=on (make coin chute 1 & 2 the same coin value, important to be "on" if using the 1 coin 9 credit option).
    • DIP 20=on (chimes/tones when scoring).
    • DIP 21=on (show high score to date).
    • DIP 22=on (award 3 credits when high score beat).
    • DIP 23=on (play a tune when money inserted).
    • DIP 24 not used.

    Having the switches in these positions will make troubleshooting a bit easier and consistent from board to board.


3i. Free Play Option.

    When checking out the dip switches on a System1 machine, there is no provision for free play on these games. The best that can be done via the dip switches is getting nine credits per coin (or 18 credits on the center coin chute), and setting the maximum credits to 25. But there are some solutions without drilling the coin door for a credit switch, or having to put quarters in your game.

Bottom board of a System1 game, showing the diode strip.
Pic thanks to PaPinball.com

    Modifying the Switch Diode Strip.
    This modification and pictures are thanks to PaPinball.com. By far this is the easiest way to add "free play" to a Gottlieb System1 game. Just solder a wire from the coin door credit button wire to any of the coin switch wires. This is done easiest at the diode strip in the bottom cabinet. Make certain that the diode, credit button wire, and coin switch wire are still soldered securely to the diode strip terminal when finished. If soldering is not an option, use a small alligator clip test lead. Now when the coin door start button is pressed, a credit will be incremented, and then decremented (because a game is started.) Now a game can be easily started without the need to open the coin door to trip the coin switches.

    Gottlieb System1 Bottom Board Diode Strip Wires:

    • Credit button wire: Green-White or Brown-Yellow-Yellow
      Connect to any of the wires below at the diode terminal strip -
    • 1st coin switch wire: Orange-White or Brown-Red-Red
    • 2nd coin switch wire: Brown-White or Brown-Orange-Orange


3j. Backbox & Playfield General Illumination.

    Unlike most other pinball makers, general illumination lights (non-CPU controlled) are not a big problem in Gottlieb System1 games.

The Gottlieb System1 T (Tilt) and Q (Game Over) relays.

    If the backbox or playfield illumination is always off, of course first check the fuses on the cabinet bottom board. The playfield lights are controlled by the T (tilt) relay, mounted on playfield underside. This relay should not be energized when the game is in "game over" mode. This relay only pulls in when game is tilted during game play. There's one set of Normally Closed contact points to turn off playfield lights in Tilt mode, and another pair to disable flippers, bumpers and slingshots.

    The other relay Q is the Game Over relay. It pulls in during game play and bookkeeping. It enables power to the playfield solenoids and flipper. The backbox "Game Over" and "Match" lights are also controlled by the Q relay. The third NC (normally closed) switch on this relay is a bit of a mystery - it disconnects the tilts switches in game over. Don't know why, maybe just a quick fix for a software problem? Or a trick to prevent players testing the sensitivity of tilt before starting a game? (more likely.)


3k. Sound board problems.

    System1 Sounds.
    In the three first System1 games there was a three tone chime unit, as used in Gottlieb's EM games. With Close Encounters this changed to a simple tone generator sound board, which still used the same three driver board transistors to generate sound. This sound board was located in the lower cabinet right next to the knocker (where the chime box was previously mounted).

The Gottlieb System1 first generation 3-tone sound board (Close Encounters).

The Gottlieb System1 first generation 3-tone sound board (Close Encounters).

    Sound improvement came with Totem, when a microprocessor controlled sound board replaced the earlier 3-tone sound board. Both the chime box or the sound boards were located in the same place, in the right side of lower cabinet. The new sound board as used on Totem and later games (multi-mode sound), though having more sound bites, was not really a big sound improvement for the System1. It had a switch that changed the sound format, much like Williams did. It also used a now unavailable Rockwell chip R3272-12. It still used the same three driver transistors from the driver board, but not in unison (as Williams and Bally did to control more than three different tones). Instead Gottlieb's MPU controlled sound board randomly picked the different sounds to play. This caused some player confusion, because a 10 point switch could have any number of different sounds.

The Gottlieb System1 second generation sound board.

    Generation2 Sound board Ground Problems.
    The +5 volts for the second generation sound board comes from an onboard 7805 regulator (center top of board) on games Totem and later. The ground connection is from two zinc plated mounting screws. These screws can corrode, causing the ground connection to be intermittent. Worse, the regulator output voltage can rise to +12 volts because of this bad ground. This can, of course, ruin the logic chips, and often the 6530 RIOT chip. The 6530 RIOT (RAM, input, output, timing) chip is no longer available and very hard and to find and expensive. And since the 6530 contains masked ROM code, it is unique for this board.

    So it is important to check and clean the 7805 regulator mounting hardware. Put some grease on the surfaces before reassembling, to prevent moisture causing any corrosion and blowing up the hard to get parts.

The Gottlieb System1 chimebox.

    Substituting Chimes for the Sound Card.
    Because of the sound card problems listed above, many operators take out the MPU controlled sound board and replace it with an older chime unit. Most players find this far more pleasing and consistent to the ear. All system1 games are downward compatible to chime coils. Be sure to use chime coils 12 ohms or greater. If coils with less resistance than 12 ohms are used, the driver board transistors Q26,Q27,Q28 will fail. If adapting a chime box from a Bally game, that should work fine as 50 volt chime coils will have higher resistance. Also don't forget to add 1N4004 diodes to the chime coil lugs, with the coil's power lug connecting to the banded side of the diode.
    • Mount the chime box right next to the knocker coil in the lower cabinet side panel near the game's power switch.
    • Route the 25 volt power from the adjacent knocker coil lug (banded diode lug), which is right next to the existing sound board (and the newly mounted chime box).
    • "Daisy chain" the 25 volt DC coil power to all three chime coils' banded diode coil lugs.
    • Now move the following wires from the sound board connector to the chime box coils' non-banded diode coil lugs:
      • orange/black/black wire goes to the 10 point chime coil lug.
      • red/brown/yellow wire goes to the 100 point chime coil lug.
      • red/green/green wire goes to the 1000 point chime coil lug.
    Remove the sound board from the game.

The Gottlieb System1 chimebox, another angle. The red wire is power,
coming from the knocker coil. Orange/blk/blk (left) is the 10 point chime.


3L. Flippers, RotoTargets, Etc.

    The flipers used in Gottlieb system1 games don't differ a lot from the flipper used in Gottlieb's 1976 to 1979 Electro Mechanical (EM) games. The major difference is Gottlieb used DC voltage on all system1 flippers, where AC was mostly used in the EM era (though some late EM Gottliebs did have DC flippers.) This style of flipper is extremely robust, and does not require a lot of work to make strong and snappy. Though many say the feel of these system1 flippers is "clunky", that is largely due to the over-engineering of the design. This means less maintenance down the road, but a heavier flipper feel during play. Keeping the mechanism clean goes a long way with these flippers.

    The flipper coils used are serial wond style - basically two flipper coils in a single package. This is typical of all flipper designs by Gottlieb. There is a high power side which does the initial flip of the ball, an EOS switch (End of Stroke), and a hold side of the coil which allows the player to hold the flipper "up" without burning the coil. A single 1n4004 diode is used to prevent coil collapse voltage from flowing back to ruining the AC to DC bridge rectifier.

    The major difference between Gottlieb EM, System 1, and System 80 flipper assemblies is the actual flipper coil used. EM games with AC power used A-5141 coils (no diode), while System 1 games (DC power) used a A-17875 coil with one 1n4004 diode. (Note some System 80/80A/80B games used A-17875 coils, but with Black Hole often the A-20095 "super flipper" coil was used.) An intermediate strength flipper coil A-24161 was sometimes seen too, starting with System 80A games.

Late EM and system1 three inch flipper assembly. This picture is actually
from a Gottlieb Jacks Open EM, but it's the same assembly as used on system1 games.
Note the nylon "finger" that comes out of the top of the flipper assembly.
Some people cut this finger off, as it can cause some additional friction.
(Gottlieb in fact did this on late system1 games.) Personally I feel if the
assembly is clean, there is no need to cut off the finger.

    The Flipper EOS Switch.
    Since a flipper coil is actually two coils in a single package, the initial power side of the coil is "turned off" by the EOS (end of stroke) switch. This switch is normally closed, shorting out the low power side of the flipper coil. When the flipper is at "end of stroke" (fully engaged), the EOS switch opens, putting both the power and hold coils in series. This allows the player to hold the flipper button, keeping the flipper "up", and not burning the coil.

    Remember that lower resistance means more power. But this also means more heat and more current draw. So the idea is to have a second "hold" part of the flipper coil, which is high resistance (and low power) in series with the power side of the coil, to decrease power consumption and heat when the flipper is kept energized. As a comparison, the high power side of the flipper coil is about 2 ohms. The hold side of the flipper coil is about 40 ohms (or 42 ohms when in series with the power side.)

    With this in mind, it's important to have a working EOS switch! If the switch is mis-adjusted and never opens, the hold side of the flipper coil will never engage, and the coil will burn rather quickly. On the other hand if the EOS switch is dirty, burnt or broken, and is never really closed, the flipper will be very weak. Because of these issues with EOS switches, they are by far the biggest problem with flippers.

    Another link in the chain is the cabinet flipper switches. These are player controlled, but they too can have problems (breakage, dirty, mis-adjusted.) The cabinet flipper switches complete the flipper power path to ground, so if they have problems, weak or non-working flippers result.

    System1 Flipper Parts.
    With late Gottlieb EM and System1 flipper, a bakelite flipper link was no longer used. Instead Gottlieb went to nylon plastic parts on the coil plunger. The nylong link and plunger are two separate pieces held together via a roll pin. Two nylong (upper and lower) flipper bushing or bearings are used, and the flipper shaft goes through these. This design is unique to Gottlieb, and it's why their system1 flipper have that certain "tank like" robust feel. (The actually weight of all these parts is greater than say Williams flipper parts, giving the flipper this "thick" Gottlieb flipper feel.)

    A plastic triangular actuator is used to open the EOS switch, thus turning on the "hold" side of the flipper coil. The only major weakness to this design is how the EOS switch is actuated - the EOS switch is opened via the flipper crank / pawl assembly, and it's a metal-on-metal contact point. As we all know, metal to metal provides a good wear point, and this is something that should be evaluated on every Gottlieb system1 flipper. The flipper crank can wear a hole in the EOS switch blade. (Gottlieb did fix this issue in the late 1980s around during production of the system80 TX-Sector game.) Frankly I personally have not seen many worn EOS blades on system1 games (30+ years after they were made), so this isn't a huge issue.

    The only system1 flipper design change was a different flipper link on 3" flippers. The molded plastic flipper link used on earlier System 1 games had a "finger", which protruded through a hole in the bearing bracket. The finger was used to center the motion of the flipper plunger. But the flippers wear with age, the finger can drag a bit through the hole. This can cause a slightly less powerful flipper. For this reason, some people cut or grind the finger off the link. Personally I feel if all the other parts (the nylon bushings/bearings) are in good shape, this is not necessary.

    Not on some System 1 games, such as Joker Poker, Count-Down, and Genie, ther are also 2" flippers. The 2" System1 flipper design is the same mechanism as Gottlieb EM games, using a standard plunger and bakelit link. (The flipper coils are different too, with system1 using an A-17875 coil.)

    Weak Flippers.
    The most common complaint in any pinball machine is weak flippers. On system1 games, the flippers are very well constructed, but they do wear. The single biggest cause of weak flippers are dirty or mis-adjusted EOS (end of stroke) switches on the flipper assemblies. Also dirty cabinet flipper switches. These are high current tungsten switches, and can be re-faced with a file. (They are NOT switch matrix switches.)

    The flipper EOS switches should open about 1/8" when the flipper is at full stroke. Any less of a gap, and the flipper coil may never engage the low power side of the coil, burning the flipper coil. If the EOS switch gap is too great, flipper strength is compromised.

    Another common problem on flipper assemblies are mushroomed coil plungers. The metal plunger, which slams into the coil stop with every flipper plunge, takes a lot of abuse. The plungers can be removed and the mushroomed end filed smooth. Also replacing the flipper coil sleeve is a very good idea.

Right side System1 flipper.

Left side System1 flipper.

Roto-Target from Close Encounters.

Roto-Target from Close Encounters.

    Gottlieb Rubber Sizes.
    Gottlieb lists rubber part numbers in their manuals, but does not indicate the actually sizes and types of rubber. So below is a list of the rubber parts and sizes.

    Part#Rubber Type
    #E-15Rubber Tip
    #986Rubber grommet - drop target
    #1872Rubber plunger tip
    #2752Rubber grommet - chime
    A-1344Rubber rebound
    A-5240Rubber grommet
    A-10217Rubber ring 3/8"
    A-10218Rubber ring 3/4"
    A-10219Rubber ring 1"
    A-10220Rubber ring 1-1/2"
    A-10221Rubber ring 2"
    A-10222Rubber ring 2-1/2"
    A-10223Rubber ring 3"
    A-10224Rubber ring 3-1/2"
    A-10225Rubber ring 4"
    A-10226Rubber ring 5"
    A-13149Flat beaded rubber ring - 2" small flipper, red
    A-13151Rubber ring - 3" flipper, red
    A-14793Rubber ring - mini post, 23/64"
    A-15705Rubber ring - mini post, 27/64"
    A-17493Rubber ring 7/16"

    Gottlieb Wire Colors.
    Gottlieb had a unique situation where they owned an actual wire color line striper. That is, they could buy white wire, run it through their wire striper machine, and get up to three colors striped on the wire. A pretty cool machine that worked great for PVC plastic coated wire. Anyway, Gottlieb used a system of three colors for their wires, and each color has a number associated with it. So a wire that is coded 012 means it's a white wire with a black, brown and red trace. All wires are coded like this except for the ground wires, which are green plastic with a yellow strip (color 54.)

    Gottlieb Wire Colors Decoded
    Color Code#
    Black ------ 0
    Brown ------ 1
    Red ------ 2
    Orange ------ 3
    Yellow ------ 4
    Green ------ 5
    Blue ------ 6
    Purple ------ 7
    Grey ------ 8
    White ------ 9


3m. The Curious Case of Pinball Pool.

    Gottlieb's system1 game "Pinball Pool" is essentially a reissue of their very successful 1973 EM game "Hot Shot" and "Big Shot" (four versus two players, respectively.) Gottlieb did update the new Pinball Pool a bit though with a center captive ball, and two upper side kick out holes (which scores the bonus and resets the drop targets, after they are all knocked down.)

    The system1 flavor of this game is quite good. In fact, it's probably better in a lot of ways than the original. One way that it's different is related to the fourteen drop targets; they can be set (using a separate 3 or 5 ball under-the-playfield plug) to drop adjacent targets. That is, if the game is set to 3 balls, hitting the left side "1" drop target will also automatically drop the right side "15" drop target. And if the right side "14" drop target is hit, the corresponding left "2" drop target will fall. Note if the game is set to 5 balls, then only every other left targets 1,3,5,7 will drop their corresponding right 15,13,11,9 targets, and targets 2,4,6 and 14,12,10 are independent.

    What is unique is the drop target change between 3 and 5 balls isn't a CPU board DIP switch, but is instead an under the playfield plug. So when changing the game from 3 to 5 balls on the CPU board, the under playfield plug should also be changed (assuming you want the drop target rules to follow the ball number change.)

The under-playfield drop target adjustment plug for 3 or 5 balls per game on Pinball Pool.

    But wait, we're not done. In order for the game to do the unison drop target falls, Gottlieb uses a "pancake" coil (A-19217) on the drop target assemblies. Each and every drop target on the Pinball Pool has one of these drop target trip coils, which allows any drop target to be automatically "dropped" (without a ball hit.) So that's 14 additional coils in a Pinball Pool that other Gottlieb system1 games do not have.

Each drop target has a "pancake" coil (A-19217, red arrow) to allow auto drop target falls.

    So this begs the question, how does Gottlieb control 14 trip coils when their driver board can barely control eight coils (including the three chime coils/sound drivers, knocker coil, outhole coil, game over and tilt relays, plus two drop target reset coil pairs and the unique "B" relay), without using under-playfield mounted transistors? (Note there's already one under playfield mounted transistor on Pinball Pool, for the drop target reset bank coils.) It's an interesting question. How would Gottlieb do this without additional hardware and software control? Well the answer is a bit odd - they do it via mechanical switches and an added "B" relay.

    Check out the picture above and notice the switches used on the drop target assembly (blue arrow.) For example when the "15" drop target falls, the above switch (blue arrow) momentarily closes. This switch then closes the power circuit to the "1" drop target coil, causing that target to fall automatically when it's partner (the "15" target) falls. The under-playfield plug adjustment connects all right and left drop targets in pairs (if set to 3 ball). If the plug is set to 5 ball, every other drop target is wired in pairs.

The "B" relay, which is unique to Pinball Pool, and cuts power to the drop target trip coils.

    But what happens when the drop target banks are reset at game/player/ball start? This is where the added "B" relay comes into play. When the game needs to reset the drop targets, the "B" relay pulls in. This opens the lone normally closed switch on the relay, turning off the power to the 14 drop target trip coils. If this didn't happen when the target banks were reset, it would also automatically cause some of the drop targets to fall via the drop target coils.

The schematics for the drop target trip coils on Pinball Pool,
and how they are wired to the adjacent drop target momentary switch.
Notice the normally closed "B" relay switch in the circuit amd the
3/5 ball adjustment under-playfield switch.

    So what does this all mean? Well if you smell a coil burning during game play, it could be one of the drop target trip coils baking. This is easy to do if one of the drop target switches are adjusted closed (see picture above, blue arrow.) Or if none of the drop targets fall automatically in unison, that could be the lone "B" relay switch is mis-adjusted. Keep these things in mind when working on a system1 Gottlieb Pinball Pool.


3n. Miscellaneous Problems and Fixes

    Problem: Can't add more than one credit to the game, or bookkeeping memory appears to be blanked, or replay scores cannot be set.
    Answer: Replay scores and bookkeeping values are stored in the CMOS RAM on the CPU board at Z22. Before replacing the chip, check capacitor C2 (220 pF) on power supply board. A bad C2 cap can cause noise in +5V supply voltage, which prevents the Z22 RAM from working. Also replacing C24 (0.01 uF) on CPU board is a good idea, which is the buffer cap to the RAM.

    Problem: Game goes to "GAME OVER" during play for no apparent reason.
    Answer: Check the two normally closed SLAM switches for adequate pressure. One of the slam switches is mounted inside the coin door, the other is at the ball roll assembly inside the cabinet. Improperly adjusted switches will respond to game vibration levels and show this problem. Also check the suppression diodes across the pop bumpers, flippers and slingshot kicker coils. An open or broken diode/older connection can cause random game-over symptoms.

    Problem: On a Genie I have a display problem: the 1000s digit on player 1 & 3 slightly glow and makes it hard to read the proper number. I also noticed that when a game is started and you have the flashing "0" for the player 1, then the 1000s digit will also light up the same as the credit display.
    Answer: The Z21 (7408) chip on the CPU board was bad.

    Problem: While resetting the score levels stored in memory, holding the credit button in fails to increment the score setting.
    Answer: This problem and others which may occur while adjusting score levels can be prevented by ensuring that all drop targets are reset before attempting to adjust the score levels.

    Problem: My game does strange things.
    Answer: Unusual or erratic behavior, especially after game has been on for long time, may be caused by overheating game PROM Z23 on the CPU board. This bipolar PROM gets quite hot, and can cause a game to do very strange things. Try attaching a small heat sink to the PROM with some superglue. Since the game PROMs are hard to find, it is also a good idea to lengthen its life even if you dont have problems. It seems that some PROM chips are more sensitive to heat than others. Alternatively replace the game PROM with a 2716 EPROM adaptor board.

    Problem: Coils or driver board transistors get very hot.
    Answer: Gottlieb System 1 games suffer from grounding problems. The solenoid ground can rise above logic ground, causing driver transistors to conduct continuously. Solenoids may work but get stuck or overheat. To fix this, make sure you have done all the mandatory ground modifications outlined in this document.

    Problem: Game starts, gives ball to shooter and freezes.
    Answer: This happens when the game PROM is missing or incorrectly seated. Also check resistors R122-R131.

    Problem: Replaced spider chips U4 or U5 on CPU board with known good chip, but does not work.
    Answer: These two chips contain the game operating system ROM, and must be of the same revision. The revision levels that work together are:

    • U4 A1753-CC works with U5 A1752-CD
    • U4 A1753-CE works with U5 A1752-CF
    • U4 A1753-EE works with U5 A1752-EF

    Problem: Buck Rogers "thinks" it needs to score. Start a game, and it continuously increments the 100s count score. The ball is ejected, and the game starts counting up points. There are times when this doesn't happen. But when the first score is made, i.e., the ball going over a switch, then the scoring just keeps on going. Makes for an intersting ball, but makes the game useless. Check ALL switch matrix inputs with a logic probe for a stuck switch, and NO switch matrix inputs are sending anything to the MPU to tell it to start scoring. Checked the output of the inverters (Z9 and Z28) to see if one of them is sending something to U5. The inverters are working fine.
    Answer: the game PROM chip was bad. Replaced it with a known good game PROM and now the game and CPU board work fine. Was able to clean the legs on the old PROM and reinstalled, finding that it now worked too.



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