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. Please remember that System80 and System80a used different power trains and power supplies than System80b, though the basic theory and mode of operation are the same. Also many of the fixes and upgrades in this section are mandatory for proper long-term operation of a System 80/80A/80B power supply.

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 (an an outlet plug), and then to the pair of transformers. Not Gottlieb does not use a MOV on the line filter (unlike Bally and Williams), so there is no surge protection in system80 games.

The two transformers convert the 120 volts AC input to other voltages needed for the game. The large transformer (C-19552) outputs power for the solenoids (24 volts and on some games 38 volts), general illumination light power (6.3 volts), and CPU controlled light power (6 volts). The small transformer (B-19548) outputs the main score display voltage (60 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).

System80/80a: The power supply path starts in the lower cabinet on the "bottom panel". The big orange power supply capacitor in the lower right corner can be seen here. Replace this capacitor IMMEDIATELY (use 10,000 mfd at 20 volts or higher). This particular bottom panel is from James Bond.

The transformer outputs only AC voltages, but the game largely uses DC volts. So most voltages (except for the general illumination 6.3 volts AC) go to bridge rectifiers or power supply diodes that convert the AC to DC volts. There are three bridge rectifier on the bottom panel, all being 35 amp 400 volt lug style bridges):
• 12 volt bridge which is used for the sound board and ultimately ends up as +5 volts for the logic voltage.
• 6 volt bridge which is used for the CPU controlled lighting.
• 24 volt bridge which is used for the playfield coil voltage.
• Some later sys80/sys80a games (like Haunted House) have a fourth bridge for 38 volts DC. This higher voltage was used for some of the coils.

After the power is converted from AC to DC via these three bridge rectifiers, it goes through bottom panel mounted fuses. Also the voltaged 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 6 volt DC lights
• Sound board power 12 volts DC
• Logic power 12 volts DC
• Coil power 24 volts DC
• Score display 60 volts AC

There are other sys80 fuses beside the bottom board fuses, all mounted under the playfield. There is usually a fuse for each of the pop bumpers and other major coil items like upkickers and drop target reset banks. In fact, there can be a whole slew of fuses under the playfield. So many that the novice can be quite over-whelmed by the sheer number of fuses. And as the games got more advanced, there are more fuses (Haunted House/Black Hole for example have a ton of under-playfileld mounted fuses.)

Under the playfield fuses for James Bond. Not too bad really. As the games get more complicated, there can be A LOT more fuses under the playfield than this.

My advice for this 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.

Fuses are designed as the weakest link in the chain. Fuse tend to blow for a reason, but they can "just die" due to fatique 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 and 5/12 volt 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".

To test a bridge a DMM (digital multi-meter) is needed. Set the DMM to diode test, and put the red lead on the ground lug of the bridge. (On system80 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. 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".

Now put the black DMM lead on the positive output of the bridge. This is again easy to find as its 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. 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.

Mounted under the playfield are two relays (or sometimes three like on Haunted House/Black Hole). This is much like what Gottlieb did on their earlier system1 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 on James Bond.

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 your 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 (like adjusting flippers or testing a Pop Bumper Driver Board).

Note games like Black Hole and Haunted house used a third under-the-playfield mounted relay ("U"). This relay would turn on the special lighting for the lower playfield, turn on the power to the lower playfield flippers, and turn off the power to the upper playfield flippers. Interestingly Gottlieb used coil voltage (24 volts) to power the #313 lamps for illuminating the lower playfield on Black Hole/Haunted House.

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 (like on the prior System1 games). This means if this switch is open, or the connectors/wiring from the CPU board to this switch are broken/corroded/failed (common problem, due to CPU board battery corrosion), the game will NOT work! This is important to know as it's different than other pinball makers. I should also mention it's really a good idea to do the slam switch modification to the CPU board to prevent future slam switch problems related to connectors and wiring. Note that on sys80b games Bad Girls, Big House, Hot Shots, and Bone Busters the slam switch is normally OPEN, as Gottlieb saw the light and conformed to the way other manufacturers used the slam switch.

The coin door on James Bond showing the normally closed Slam switch.

In addition to the slam switch, there are of course "normal" tilt switches in system80 games. The ball roll tilt (just inside the coin door area) is a Normally Open style tilt (unlike the prior System1 games that used normally closed). And of course the pendulum tilt is typical of all pinball games. Both these switches must be open for the system80 game to function. Finally there's a playfield mounted weighted tilt switch too, which also must be open. These tilt switches are all in parallel, and will show as switch 26 being closed in the self-test if ANY of them are closed.

The ball roll and pendulum tilt switches on a system80 game (James Bond). Both of these switches must be normally open (not making contact) for the game to play.

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 closed.)

The last stop on the system80 power supply train is the power supply board in the backbox. This takes "raw" unregulated voltages from the bottom panel and converts it to regulated voltages. This means if your wall voltage is 110 volts or 125 volts it does not matter, the regulated 5 volts (for example) will be 5 volts (no more, no less). On system80/80a, there are a few modifications that should be preformed to the power supply for reliable long term operation.

The logic ground on the power supply board also to be tied to the metal heat sink plate of the power supply (which will be eventually wired directly to ground for a good reliable connection). This is part of the infamous Gottlieb grounding problem, which is evident on both System80 and System1 Gottlieb games.

The System 80/80a Power supply, front and back views. Note the huge metal heat sink plate the board is bolted to.

Gottlieb also made a mistake when designing the System 80 power supply, causing the diode CR7 to burn. They shouldn't have made this mistake; their System 1 power supply (which is almost identical to the newer System 80 design) did not have this mistake!

Many System 80 power supplies had the standard Gottlieb manufacturing error of having the component leads cut too short. Gottlieb cut the leads into the solder meniscus (solder mound) that builds up around each component lead. This can cause the solder joint to crack and fail.

Power supply solder defects. Note the puckered solder pads.

Lastly, replacing the larger ORANGE power supply capacitor in the bottom of the cabinet is a very good idea! This will ensure the +5 vdc logic power will be nice and smooth. If this capacitor is bad, the game can reset during play. Computer grade 105 degree capacitors work great for extended life. Any value from 6800 mfd to 15000 mfd can be used, as long as the voltage is 16 volts or better. Ideally, 10,000 mfd is a good value to use. Capacitors larger than 10,000 mfd put added strain on the bridge rectifier. The "inrush" current required to initially charge the larger capacitor can prematurely destroy the bridge rectifier.

System 80B Power Supply Problems.
The system80b power supply is a small board with a large heat sinked transistor, two .156" six pin Molex connectors, a resistor and cap, and a trim pot. REPLACE THE 500 OHM TRIM POT. Really no joke that pot is junk, and can cause the power supply to jump from 5.0 volts, to 7 volts, down to 4 volts (yes I have seen this happen). This can obviously play havoc with the game, and even ruin the board(s). Or replace the trim pot with a 1/2 watt resistor of about 270 ohms (non-adjustable, but there's no worry about the voltage drifting). You may have to experiment to get the correct resistor value. Measure the +5 volts on the CPU board at the input electrolytic capacitor near the +5 volt power connector, it should be 5.0 to 5.2 volts DC.

The system80b power supply also has two 6-pin .156" Molex connectors. 12 volts comes into the power supply at the lower Molex connector, and +5 volts goes out at the top Molex connector. One pin of the top 6-pin connector goes to each board in the backbox, supplying +5 volts to the boards. Because of this, the top power-out connector is often burnt. Replace the power supply board's .156" header pins. Then use Molex trifurcon pins in the plastic connector housing (the original connector housing can be reused).

Another trick is to just replace the system80b power supply with a video game switching power supply! Just hang the switcher from the inside top of the backbox, supplying +5 volts to all the wires previously attached to the top system80b power supply Molex connector. Connect ground to the ground strap in the backbox. Run 120 volt wires to power the switcher. Don't forget to adjust the switcher's +5 volt trim pot to 5.0 to 5.2 volts.

It is also a good idea to replace the 10,000 mfd 25 volt filter capacitor by the transformers and bridge rectifiers in the bottom cabinet. This cap can also be tested with a DMM set to AC volts and attached to the leads of the 10,000 mfd filter cap. If more than .50 volts AC is seen, this capacitor is worn out and should be replaced.

Testing the System80 and System80A Power Supply.
Before doing any modifications, it's good to know if the power supply (in its current state) works. Here is a good way to test a System80 and System80a power supply. Heck, if the system80 game in question has never been turned on (since you bought it!), this is a good generalized way to "bring her up", without smoke and fire.

Power Supply Test, Step One:
• Check all fuses in the bottom panel of the game. Make sure all are the proper rating and type!
• Remove ALL connectors from ALL boards in the backbox.
• Attach power supply connector J1.
• Power the game on.
• Notice the two LEDs DS1 and DS2. One signifies unregulated 12 vdc is coming into the power supply. The other LED signifies +5 volts is coming out of the power supply.
• Check the output voltages at TP4 (+5), TP5 (8 vdc), TP1 (60 vdc), TP2 (42 vdc), using TP3 (ground) for a reference.
• Turn the game off.
Voltages can be higher than expected. For example, seeing 48 volts for the 42 volts test point, 65 volts for the 60 volts, or 8.6 volts for the 8 volt test point are all Ok. But +5 volts should be in the 4.8 volt to 5.2 volt range (there is a trim pot to adjust the +5 volts).

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

• Attach the connector from power supply J2 to CPU board A1-J1.
• Power the game on.
• Check the output voltages at TP4 (+5), using TP3 (ground) for a reference.
• Turn the game off.
This step makes sure that the +5 volts is not dragged down by the CPU board. If +5 volts goes down, try adjusting the power supply trim pot. If voltage is still below 4.8 volts, this will need to be fixed.

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

• Attach power supply connector J3. This is the displays and playfield power connector.
• Optional: Attach the CPU board connectors A1-J2 and A1-J3. These are the connectors going to the displays.
• Optional: Attach CPU board connector A1-J5. This is the slam switch and test switch connector. Note: this step not required if the "slam switch mod" has been performed on the CPU board.
• Power the game on.
• Check the output voltages at TP4 (+5), TP1 (60 vdc), TP2 (42 vdc), TP5 (8 vdc), using TP3 (ground) for a reference.
• Turn the game off.
If 60 volts and/or 42 volts are now missing, there is probably a shorted score display! This is fairly common. Replace the 60 volt fuse in the bottom panel (it may or may not blow!), and disconnect all but ONE of the score display connectors (don't forget the score display in the playfield on Black Hole and Haunted House). 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.

Mandatory Parts Needed:
• (1) 680 ohm, 1/2 watt resistor (for R10).
• (1) 12k ohm, 1/2 watt resistor (for R3).
• (1) 1N4738 zener Diode 8.2V, 1 Watt (for CR7).
• (2) Molex .156" square header pins, part# 26-48-1125, cut to size.
• (2) Molex .156" crimp-on connector housing, part# 09-50-3121, cut to size.
• (20) Molex .156" Trifurcon terminal pins, part# 08-52-0113 (Digikey part# WM2313-ND).
• (1) 6800 mfd to 15,000 mfd, 16 volt (or higher) capacitor (10,000 mfd is the ideal size to use). A computer grade 105 degree capacitor is a good replacement.
• 3 inches of 18 gauge wire.

Optional (but recommended) Parts Needed:

• (1) 1N4746 zener Diode 18V, 1 Watt (for CR6).
• (1) 470 ohm sealed resistor trim pot.
• (2) LEDs yellow, orange or red.
• (1) 14 pin socket for regulator chip.
• (1) UA723CN regulator chip, but can use LM723CN, LM723CD, NTE923D (or something similar since these chips are common, and Radio Shack sells these). This is used with the 14 pin socket, above.

Power Supply Disassembly Instructions:

• Remove the power supply board from the head box. The board includes a large black heat sink plate behind the printed circuitry board (PCB).
• Test the large metal power transistor (PMD10K40, 2N6057, 2N6059, NTE247, NTE249) installed on the back plate of the board. Set the DMM to the "diode" setting. Then put the black lead on either attachment screw of the transistor (which is connected to the metal case of the transistor), and the red lead on each leg. A reading of .4 to .6 for each transistor leg should be seen. Anything else and this transistor is bad.
• On the heat sink plate side, remove the 2 screws from the large transistor.
• On the heat sink plate side, remove the 4 screws from the corners of the plate.
• De-solder the two legs of the large transistor labeled Q3.
• Gently pull the heat sink plate from the board.

Left: The parts to be replaced: R10, CR7, R3. Note how hot CR7 has gotten. Right: Using the solder sucker to remove Q3. Then the metal heat sink plate can be removed, and the back of the board accessed.

Mandatory Parts Installation:
• Replace resistor R3 with a new 12k ohm 1/2 resistor. This resistor often fails.
• Replace resistor R10 with a 680 ohm 1/2 watt resistor. This will decrease the load on diode CR7.
• Check diode CR7 (the burnt part!). If damaged, replace with a new 1N4738A diode (or to be safe, just replace it).
• Re-solder all header connector pins (these often crack). If the header pins are corroded or in bad shape, replace then with new .156" (square) header pins. Also replace the plastic connector housing's pins, Molex part number 08-52-0072, crimp-on pins (see the connector chapter of this document for more info).
• On the solder side of the power supply board, solder a 18 gauge jumper wire from the ground trace to the lower attachment screw hole. See the picture below.
• Re-solder any leads that look like they were cut too short.
• Re-solder the large rivet holes that the large transistor leads go through.
• Solder clipped off resistor leads to the voltage test points (GND, +5v, +8v, +42v, +60v). This will make it easier to test voltages when the board is installed.
• Check the values of the other resistors on the power supply board to make sure they are in tolerance.
• Replace the round metal power supply pins at connector J2 with brand new .156" Molex square header pins (Molex part# 26-48-1125, cut to size). In addition, replace the 6 pin plastic housing going to this connector with a new crimp-on variety (Molex part# 09-50-3121, cut to size). Then crimp on new .156" Molex Trifurcon terminal pins (Molex part# 08-52-0113, Digikey part# WM2313-ND) to the connector wires.
• Replace the round metal power supply pins at connector J3 with brand new .156" Molex square header pins (Molex part# 26-48-1125, cut to size). Also replace the 7 pin plastic housing going to this connector with a new crimp-on variety (Molex part# 09-50-3121, cut to size). Then crimp on new .156" Molex Trifurcon terminal pins (Molex part# 08-52-0113, Digikey part# WM2313-ND) to the connector wires.

The green wire on the power supply board is soldered from ground to the screw attachment hole.

Left: The transistor rivet holes that need to be re-soldered. Note the complete lack of solder around part of the circumference. Right: A test point after soldering a clipped-off resistor lead in place.

Optional Parts Installation:

• Highly Recommended: Replace the 500 ohm trim pot on the power supply board. This old pot gets dirty, and the output voltage can jump around because of it. Replace with a high quality, 470 ohm unit.
• Install a new 1N4746 zener diode (18 volt) for CR6.
• Replace the old LED's on the power supply board with new ones. With age, the old LED's get dark and can "sink" (consume) far more current than new ones. Also change the colors of the LED's. For example, use orange or yellow LED's (but not green or blue!) so one can tell at a glance if they have been changed.
• Install a 14 pin socket for the regulator chip. This regulator chip is often bad, causing the +5 volt power section to fail. Just socket the chip so the the whole power supply doesn't have to be torn apart when it goes bad.

Finishing (re-assembling) the Power Supply.

• Make sure the large Q3 transistor's plastic insulator is in place. This plastic part ensures the legs of the large transistor do not short to the metal heatsink plate.
• Make sure there is a mica insulator underneath the large Q3 power transistor.
• Re-assemble and screw the heat sink plate back onto the PCB. Re-solder the large transistor's leads.
• Using a DMM, make sure there is *no* continuity between the metal case of the large Q3 transistor and the metal heatsink plate. If there is continuity, please re-verify the above first two steps.
• In the bottom of the cabinet next to the transformer, replace the ORANGE 6800 mfd 1" diameter by 3" tall power supply capacitor with a new unit. See below for more details.
• Test the power supply's voltages. After doing the above mods, install the power supply board back into the game. Connect only the lower plug J1. Turn the game on. Note the two LED's on the power supply board should be lit. Using a DMM, check the DC voltages at the connectors points on the board: +60, +42, +8 and +5 volts DC. When all the voltages are present and verified, turn the game off and re-connect all the disconnected plugs. Power the game back on, and measure the +5 volts DC again. Adjust the trim pot to 5.1 volts.

2N5550 in the High Voltage section.
In the high voltage section of the Gottlieb sys80/80a power supply, a 2N5550 transistor is used. If this goes bad, it can be replaced with a 2N5551 (more common and more robust). Both parts cross to NTE194.

Sys80/Sys80a: Replace the ORANGE 6800 mfd filter cap in the bottom of the cabinet!
There are two large capacitors here; replace the one WITHOUT the resistor across the leads (note on some system 80b games such as Jacks Open, Gottlieb used *two* large orange capacitors with no resistor wired in parallel, instead of just one). No exceptions here, the orange 12 volt filter capacitor(s) need to be replaced. Any value can be used from 6800 mfd to 15,000 mfd at 16 volts or higher (again on system 80b games like Jacks Open with two orange capacitors wired together, these two can be replaced with one single capacitor). Ideally, 10,000 mfd is about right. Capacitors larger than 12,000 mfd put added strain on the bridge rectifier. The "inrush" current required to initially charge the larger capacitor can prematurely destroy the bridge rectifier.

The original capacitor can be tested (but don't bother, just replace it!) To test the capacitor, turn the game on, and set the DMM to AC volts. Put the leads of the DMM on the leads of the filter cap. If after a few seconds (after the voltages stops fluctuating) there is more than .2 volts of AC, this capacitor is bad. Again, if using the original orange filter cap, I would highly recommend replacing it regardless of its AC reading.

Remember when hooking up the new capacitor, do *not* mix up the positive and negative wires going to the new capacitor!

Other Tips (Missing +5 volts).
There are two LED's on the power supply board. One for +12 volts, and the other for +5 volts. If the +12 volts is not lit, then the +5 volts won't be either! If only missing the +5 volts, I would suspect the voltage regulator UA723CN (NTE923D) chip first, or the PMD10K40 (Q3) transistor. But hopefully Q3 was tested in the previous procedure. Make sure Q3's transistor bolts are tight, and Q3 is soldered well to it's circuit board eyelets. Also make sure there is no continuity between the metal plate and Q3's metal case.

Still no +5 volts, then check SCR1 (S107Y1). This device's job is to check turn on and short +5 volts to ground, if +5 volts goes above 6 volts (as a protection measure to the circuit boards). The SCR can be tested (with the power supply off, connectors removed) using a DMM set to diode setting. Measure between TP4 and ground (red DMM lead on ground), and .3 to .5 should be seen.

Also note power supply transistor Q1 (NPN, SW4F013) can be replaced with a TIP31c transistor. More power supply repair information can be found at http://www.geocities.com/kirbseepe/repairpowersupply.html.

System 1 Power Supply Problems.
This document gennerally does not cover Gottlieb System1 games. But since the System1 power supply is so close to the System80 design, I thought it prudent to add some System1 info. See marvin3m.com/sys1 for more System1 repair info.

• Make sure that Q1 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 is bad.
• If no +5 volts, check pin 7 of IC1. 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 very hot and there is no +5 volts, then SCR101 is bad.

The four bridge rectifiers and two electrolytic capacitors in the bottom panel of System 80 games. The original +12 volt filter electrolytic 6800mfd capacitor is smaller and usually orange. This needs to be replaced. This replacement is a computer grade cap.

Bridge Rectifiers.
In the bottom panel of the game, there will be four bridge rectifiers and the two large electrolytic capacitors. The capacitor used for the +12 volts (and ultimately for the +5 volts) is the one that should have been replaced in the above steps. This is the capacitor without the resistor across its leads. The other capacitor smoothes the higher voltages for the solenoids, and is far less critical.

The 12 volts bridge rectifier. Notice the near left lead (orange wire) is oriented different than the other three leads. This is the DC positive output lead.

Sometimes bridge rectifiers die. If turning on your game immediately blows a fuse, this could mean a shorted bridge rectifier. For example, if the F4 fuse blows immediately at power up on Haunted House or Black Hole, this probably means the connecting bridge rectifier in the bottom cabinet has shorted.

Bridges can be tested easily. But first the leads of the bridge will need to be identified. Each bridge has four leads: two input AC leads, and two output DC leads (positive and negative). One of the legs on the bridge will be in a different orientation than the others; this is the DC positive output lead. The DC negative output lead is directly opposite (diagonal) to it. The remaining two leads are the AC input leads. Also, the two output DC leads should go to the electrolytic capacitor's positive and negative leads.

Testing a Bridge Rectifier.
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.

Replacing a Bridge Rectifier.
If one of the bridges tests bad, replace it. Get a 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.

The system80B 5vdc power supply is pretty simple. Other than the LM338 voltage regulator and a couple resistors/caps, there's not much to check. But one thing I would HIGHLY recommend is replacing the 500 ohm trim pot on this power supply, which adjusts the +5 volts. The quality of this pot was bad when new. Add 20+ years and things have only gotten worse. I once saw someone adjusting this pot and crash the CPU board because the original pot had a "flat spot", and put up to 12 volts to the CPU board. Don't mess around with this pot, just replace it.

After the pot is replaced and the power supply installed back in the game, check the +5 volts and adjust it to 5.10 volts DC, with the CPU board disconnected (left most CPU board small power plug removed). After the power supply is adjusted, power off and re-connect the CPU board, and check the +5 volts again for 5.10 volts DC. Be very careful when adjusting this 5 volt trim pot. The big problem with the sys80b power supply is a lack of a "crowbar" safety circuit. That is, if the power supply fails it can send upwards of 12 volts through the 5 volt circuit, ruining everything in its path (there is no zener diode to protect the 5 volt circuit from over-voltage).

The Gottlieb System3 and System80b +5 volt power supply. The one offending component on this unit is the low quality500 ohm trim pot, which should be replaced with a quality version.

While working on the System80B power supply, resolder the connector header pins, as often these will crack. I also suggest to re-pin the .156" female connectors with new Trifurcon Molex connector pins. And lastly, don't forget to do the ground modification to this power supply (adding a ground wire to J1 pins 1,2 on the power supply), while you have it removed from the game.

Important note: While doing the following mandatory circuit board modifications, please inspect each board to be repaired for these defects, and correct them.

Many early System 80 boards (Haunted House and prior) had the standard Gottlieb manufacturing error of having the component leads cut too short. Gottlieb cut the leads into the solder meniscus (solder mound) that builds up around each component lead. This can cause the solder joints to crack and fail.

To correct this problem, resolder component leads where the solder meniscus has been cut. This defect is evident on both single sided and double sided circuit boards.

Look closely at this board: Can you see the plated thru holes where there's no solder, or the solder is "puckered"? Also note the solder around the component pins. Some of these pins are puckered or completely open. All these need to be re-soldered.

Another manufacturing error was that the boards were waved soldered at too low a temperature. This created problems on double sided circuit boards in the plated-thru holes. These holes let a trace move from one side of the board to the other. If these holes aren't filled with solder, this can cause intermittent connection problems. This is very common especially at holes near the edge connectors.

To correct this problem, look at the "via" (plated thru holes) and if the solder is puckered or missing (!), resolder these holes and add some new solder. To ensure complete reliability, stitch a piece of wire-wrap wire thru the holes and solder on both sides of the board.

The Gottlieb DataSentry battery. This battery has leaked only slightly (note the corrosion to the crystal). This board was lucky. Also shown below the battery are the Z3 (7404) and Z2 (7474) chips. These are often affected by battery leakage.

This fix is mandatory. All Gottlieb System 80 boards use a recharagable "DataSentry" 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 15+ year old rechargable battery is mandatory!

Remote AA battery pack and 1N4004 blocking diode, connected to a System80 CPU board (original battery removed).

New Remote AA Battery Pack.
To replace the original battery, add a remote three "AA" battery pack and a 1N4001 or 1N4004 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 will work fine with no battery. Not having a battery means that the high scores and operating audits won't be saved. Personally, I find this acceptable, but the memory can come up with wacky high scores (digits misformed or missing). Also always remember to check the 5101 chip Z5 pin 22 (ground is the reference) for battery voltage using a DMM after installing the new remote battery pack. This confirms you have the battery connected right.

An installed memory back-up capacitor. After the battery is removed, the traces are sanded shiny. The negative lead of the cap is put in the negative battery hole. The positive lead is bent, and soldered directly to the trace leading to the positive battery hole (since the positive battery hole was too far away).

Memory Back-Up Capacitors.
If one insists on having a battery (can't live without those high scores!), a decent alternative 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. Also, the game must be on for about about 8 hours continuously to initially charge the capacitor. These capacitors are about the size of a stack of nickels. Jameco (800-831-4242) sells 1 Farad memory caps, part# 142957, $3.95 each, $3.49 for ten or more.

Note that some CPU boards will work better with a memory cap than others. This has to do with the exact memory on the 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 well with a backup cap, and others may not. "Your mileage may vary" is probably a good statement about memory backup capacitors.

When I installed my back-up capacitors, the minus and positive leads were 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). Always check the 5101 chip Z5 pin 22 for battery voltage using a DMM. This will confirm you have the new battery or memory cap connected correctly.

If the installed memory cap/battery doesn't seem to work (and it was installed correctly!), check the issolation diode CR34. Do this using a DMM set to diode test, with the game off. Black DMM lead to the banded side of the diode, red DMM lead to the non-banded side. Should see about .4 to .6 volts on the DMM. Sometimes the CR34 diode will short (showing .002 or the like), and should be replaced with a new 1n914 or 1n4148 diode. 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.) If the CPU batteries or memory cap is dying quickly, the problem is often either a bad CR34 diode (1N4148) or a bad Z1 CMOS chip (4528). Note these parts are included in Ed's battert corrosion kit below.

Reset Circuit Check.
The reset circuit is the most vulnurable part of the CPU board in regards to battery corrosion. To determine if the reset circuit is working on a CPU board is pretty easy. Connect the CPU board to +5 volts (the left most CPU board 5 pin connector), and then check the 6502 pin 40 for +5 volts. If this pin is 0 volts, the reset circuit is not working. If 6502 pin 40 is 5 volts, then the reset circuit is working. Remember the purpose of the reset circuit is to hold the 6502 microprocessor's reset line pin 40 LOW (0 volts) for about 100 milliseconds. This allows the +5 volts to stablize at power-on. Then the reset circuit makes 6502 pin 40 go HIGH (to 5 volts), and the 6502 processor starts running and executing game code (and the game "boots"). So if the reset circuit is not working, the CPU board will never boot (never start executing ROM code), even if the rest of the board is fine. After the reset circuit is working, the next thing you should check on a dead CPU board is the clock signal (again, this circuit is right around the battery). See the Sys80 CPU board Repair section for more info.

Battery Corrosion and the CPU Board's Reset/Clock Circuits.
Battery corrosion can do nasty things to the left side of the CPU board. This is the "reset" section of the CPU board (and below the crystal Y1 is the "clock" section). Depending on how bad the corrosion is, many parts may be needed in these areas. Instead of ordering all those separately, I suggest just buying a "Gottlieb System80 Battery Corrosion Repair Kit" GTLB80-BA-KIT from greatplainselectronics.com. This kit includes all the resistors, capacitors, transistors, crystal and chips typically ruined by battery corrosion. For a mere $10 (plus $3.50 shipping), this kit is well worth it. If for some reason the $10 is too much money, here are the typical parts needed for a System80 battery corrosion repair (these are the same parts included in Ed's kit):

• Z1*: CMOS 4528.
• Z2*: 7474 or 74HCT74 chip.
• Z3*: 7404 chip.
• Z4*: CMOS 4081.
• Z36*: 4069 CMOS chip.
• (4) 14 pin sockets for Z2,Z3,Z4,Z36 chips.
• (1) 16 pin sockets for Z1.
• SW1: 8 position DIP switch
• C1*: 100 mfd 10 volt electrolytic cap.
• C2,C5: .01 mfd (103) ceramic cap.
• C3,C25: .1 mfd (104) ceramic cap.
• C36*: 10 mfd 10 volt tantalum or electrolytic cap.
• CR1-CR8,CR33-CR35*: 1N4148 or 1N914 diode.
• R3,R43,R49: 5.6k ohm 1/4 watt resistor (green, blue, red).
• R4,R5,R44: 2k ohm 1/4 watt resistor (red, black, red).
• R6,R45,R46,R48: 3k 1/4 watt resistor (orange, black, red).
• R7: 62 ohm 1/4 watt resistor (blue, red, black).
• R8,R50: 180 ohm 1/4 watt resistor (brown, gray, brown).
• R9: 1k ohm 1/4 watt resistor (brown, black, red).
• R34-R41, R54: 4.7k ohm 1/4 watt resistor (yellow, purple, red).
• R47: 24k ohm 1/4 watt resistor (red, yellow, orange).
• Q1,Q4*: MPS-A70 or 2N4403 transistor.
• Q2,Q3*: 2N4400 or 2N4401 transistor.
• VR1*: 1N5225b or 1N5987b zener 3 volt diode.
• Y1: 3.579545 mHz crystal.
* Polarized parts: The above components DO require installation in the "correct direction". Failure to do so will kill the part, and maybe some other parts too. And for sure the board will not work. So be careful!

Using a Dallas/Maxim DS1811 in the Reset Section.
Thanks to Pascal Janin, there is also another way to fix the reset section with just a four parts (that replaces nearly 25 parts!) This involves using the new Dallas/Maxim Semiconductor D1811 reset chip (TO-92 package). This inexpensive device looks like a transistor, but is really a three leg chip in a TO-92 transistor package. Click here or here (PDF, more info) for the specs on this chip. Cost of this chip is less than $1, and can be ordered directly from Dallas/Maxim Semiconductor at www.dalsemi.com via their phone number 888-629-4642 (but orders must be faxed in at 408-222-7174). Be sure to order the TO-92 package (part number DS1811-10), as this chip also comes in a surface mount SOT23 package.

The advantage to the Dallas DS1811 is great: if a system80 CPU board has had some battery corrosion and perhaps some circuit board traces are questionable, the new Dallas part will not utilize most of that. So even a board with lots of corrosion can have 25 reset parts cut out, and just the Dallas installed. So most of the questionable traces on the component side of the circuit board are eliminated too, making battery corrosion less of an issue.

The Dallas DS1811 comes in three TO-92 flavors of "normal reset threshold":

• DS1811-15 = 4.13v
• DS1811-10 = 4.35v *
• DS1811-5 = 4.62v
* The best one to order is DS1811-10.

Here are the installation steps for this chip:

• Remove reset parts: chip Z1, trans Q1-Q4, diodes CR33, CR35, VR1, resistors R8, R9, R43-R50, caps C2, C25, C36.
• Install a jumper from Z1 pin 5 to Z1 pin 9.
• Install a jumper from Z1 pin 11 to Z1 pin 13. Be careful not to accidentally connect pin 12 to the jumper, as it will cause the reset modification to not work.
• Install a jumper where R45 was installed.
• Install a jumper between the two top holes of Q3 (the Emitter and Base).
• Install the Dallas DS1811 (TO-92 package) into the top pads of R50, R44, R49 (pin 1=R50, pin 2=R44, pin 3=R49). Note the flat edge of the DS1811 faces downward away from Z1, toward the dip switches.
• Retain reset parts CR34, R7 and C3.
• Note R10 and C14 can be remove or left installed. Since Z1 has been removed, R10 and C14 are no longer used, and can be removed (or left installed).

The DS1811 is installed with pin 1 going to /RESET, pin 2 to +5 volts (thanks to the jumper at R45), and pin 3 to ground (via the jumpered Q3). A picture of all the removed parts and the DS1811 and jumpers installed can be seen below. Also remember using the DS1811 will not replace the often damaged clock circuit chips at Z2 and Z3.

Picture of the Dallas DS1811 installed in the Sys80 CPU board.

The Dallas DS1811 installed in the Sys80 CPU board (picture by Neil Bradley).

Another picture of the Dallas DS1811 installed in the Sys80 CPU board.

There is a side affect of the changed reset circuit: the "thunk" that is often heard at boot up on System80 games may be louder, because the reset timing is changed. The duration of the reset pulse issued by the DS1811 lasts 150ms, while the original circuitry generates a 50ms reset. This increases the startup time until the coil and lamp outputs are properly initialized, hence the slightly harder "thunk". Personally I don't really think the "thunk" is louder, but it could be different on your game.

Removing the Old Battery and Fixing Corrosion.
Here are the 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. To be completely safe, replace all the parts included in the list above (especially if Ed's kit was purchased). At a minimum, typically transistors Q2, Q3, Q4 and all the resistors around that area are damaged. Also chips Z2 and Z3 and the crystal Y1 are often damaged.
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.
11. Replace all removed components (except the battery!). Any removed chips should be replaced with a good quality socket.
12. Check the connectors themselves! If the board has corrosion, the connectors may too! Replace the connector pins if any damage is seen (see the connector section below). They can also be cleaned sometimes with scotchbrite and alcohol. But replacement is the ideal solution.

Again, order the battery corrosion kit from Ed to get all the parts usually ruined by corrosion.

Remote AA battery holder installed in a James Bond (ground mods done too).

These fixes are mandatory.

The Gottlieb Grounding Problem.
There are multiple problems with ground in System80 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 get 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 system80 games were "unreliable".

Now let's talk about the Driver board and its multiple grounds. There are several grounds on the Driver board (lamp ground, logic ground, solenoid ground, etc). Only the solenoid ground should be independent (as it was designed), and all other grounds should be tied together. The logic ground levels between the CPU and driver boards also need to be equalized (as little difference as possible between the two). Because ground between the boards are connected via a single edge connector wire, differences in ground levels can occur. If resistance develops in the connector (very common), and the difference between the logic ground on the CPU and driver board is .1 volts or higher, the CPU and/or Driver board can lock up and be damaged. This in turn can cause coils to lock on and burn. Though this is less of a problem than the cabinet and circuit board ground (see above), it is still a problem.

Prior to 12/1/99, there was a slightly different procedure in this guide for fixing the driver board ground problems. Thanks to Pascal Janin, we now have a better understanding of the problem. He documented the differences in voltages in the following places:

• Difference in voltage between the negative side of capacitor C1 (100 mfd 10v) and the connector A1J4 pin A, on the CPU board.
• Difference in voltage between the negative side of capacitor C1 (100 mfd 10v) on the CPU board and chip Z12 pin 8 on the Driver board (the furthest away ground connection).
• Difference in voltage between the positive side of capacitor C1 (100 mfd 10v) and connector A1J4 pin B, on the CPU board.
• Difference in voltage between the negative side of capacitor C1 (100 mfd 10v) on the CPU board and chip Z12 pin 16 on the Driver board (the furthest away +5 volt connection).

Ideally, as little difference in voltage as possible is desired. Pascal tested this with no modifications, the earlier modification (previously described here), and the new modifications (described below). The methods now documented here yielded the least amount of variance in the voltages.

These modifications also ensures that the solenoid ground is independent from the logic ground. This is important because if the solenoid ground fails, the solenoid high voltage could go through the logic ground, damaging circuit board components. Also, there can be "feedback" interference to the logic ground from the solenoids. This could damage circuit board components.

What are We Trying to Accomplish?
In the "mandatory" ground modification, we make sure the cabinet ground and circuit board ground are solidly tied together (the connection to ground between the cabinet, power supply, CPU and Driver board, and other boards will be made more reliable). In the "optional" ground modification, we make sure the solenoid ground is isolated from the logic ground so that all the solenoid transistors on the driver board (except Q57, Q61, Q63) will have their emitters connected together. But in addition, these solenoid transistor grounds will be isolated from the CPU and Driver board logic grounds (a good place to test for logic ground is at pin 8 of any 74175 chip on the driver board).

The Gottlieb System 80 Driver board, with added ground wire.

The Gottlieb System 80b CPU board, with added ground wire and a remote battery pack.

Driver board parts that are required:
• (4) Molex connector pins for the A3-J1/A1-J4 connector (mandatory). See the next section for part numbers.
• (10) feet of 18 gauge wire (mandatory)
• Wire wrap wire (30 gauge) or zero ohm resistors (optional)

Other driver board stuff to have around that is often bad:

• MPS-U45 transistors
• MPS-A13 transistors
• 2N3055 transistors (and connecting 9.1 ohm resistor)
• 2N6043 transistors

0. PRE-WORK: 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 take a moment to test all the transistors.

1. STEP 1: On the CPU board, find the electrolytic capacitor C1 directly to the right of the main CPU power connector A1-J1. Attach a 12" wire to the TOP lead of this C1 capacitor, and a forked spade connector on the other end of the wire. This wire is the CPU ground.

   On Sys80/Sys80A, run this added CPU board ground wire to the metal frame of the power supply.

   On Sys80B, run this added CPU board ground wire to the ground plane screw (which attaches to the yellow covered ground plane) in the lower right of the backbox.

Step 1. Sys80/80a ground from power supply capacitor C1's negative lead, to the metal frame of the power supply. And the ground from the CPU board's electrolytic capacitor C1 negative lead to the metal frame of the power supply. Picture by J.Robertson.

Note: Remember how we modified the sys80/sys80a power supply to connect ground with a jumper wire to the metal heat sink plate, in the Power Supply modification section? Well here's where that modification ties into the CPU ground. If this power supply modification step was not done, a wire can be connected from the power supply's negative lead of capacitor C1 (large electrolytic cap at the lower left corner of power supply), to the metal heat sink power supply frame connection. If the black part of the power supply frame is used, be sure to SAND the black off the frame where the wire connects to ensure a good connection.

On system80 and sys80a, connect the ground wire from the CPU board to one of the mounting bolts on the metal power supply board heat sink plate frame (use a "fork" or "bullet" connector so the CPU board can be easily disconnected). Again if the black part of the power supply frame is used, be sure to SAND the black off the frame where the wire connects to ensure a good connection. Then continue this wire to the metal lock plate in the upper left corner of the backbox. This metal lock plate also has a stock green wire (provided by Gottlieb), which continues down to the to the large copper ground bus in the bottom panel of the game (where all the green wires are soldered), next to the transformer. This is the main ground bus for the game. Optionally another wire can be added from the lock plate/metal power supply plate down to the copper ground strap (be sure to sand this copper ground area clean before trying to solder to it). Also note on some System80 games the 6 volt GI (general illumination) line runs dangerously close to the power supply frame. Make sure the bare 6 volt GI wires do *not* touch the power supply frame.

Step 1. On sys80 and sys80a, if the power supply board ground to the screw attachment hole wire modification documented above is not done, a ground wire can be soldered to the negative lead of the power supply capacitor C1. The other end of this wire and then attached to the metal ground frame of the power supply.

Step 1. This pictures shows the bottom panel of the game, and the large copper grounding strap (with all the green ground wires connected). The green ground wire attachs to the CPU and Power supply boards here.

Picture by J.Robertson.

2. STEP 2: Replace the power supply to CPU board power connector cable pins (all sys80,a,b games). On the CPU board connector A1-J1 to the power supply connector J2, replace *all* the pins on both connectors! On sys80 and sys80a, it involves replacing the round male power supply header pins at power supply connector J2 with brand new .156" Molex square header pins (Molex part# 26-48-1125, cut to size). Also replace the 6 pin .156" plastic housing with a new crimp-on variety (Molex part# 09-50-3121, cut to size). Then crimp on new .156" Molex *Trifurcon* terminal pins (Molex part# 08-52-0113, Digikey part# WM2313-ND) to the wire. On all sys80,a,b game on the CPU A1-J1 connector, replace the five pins with brand new Molex single sided terminal pins (Molex #08-52-0072). The original plastic connector housing can be re-used.

3. STEP 3: For sys80/sys80a, on the power supply connector J3 (which supplies the display voltages and display grounds), replace the entire header connector. This involves replacing the round metal power supply pins at connector J3 with brand new .156" Molex square header pins (Molex part# 26-48-1125, cut to size). Also replace the 7 pin plastic housing with a new crimp-on variety. Then crimp on new .156" Molex *Trifurcon* terminal pins (Molex part# 08-52-0113, Digikey part# WM2313-ND) to the wire. If this connector is not rebuilt, a "low-rent" modification can be preformed. Run a wire from pins 4/5 of power supply connector J3 to the metal frame of the power supply (don't forget to sand the black part of the power supply frame where any wire attaches). If this modification is not done, score display "flicker" can result (especially on any displays that are playfield mounted), and sporatic pop bumper problems (either not working at all or working strangely).

   For Sys80B, some ground modifications must be done at the lower cabinet on the metal transformer panel. On one side of this panel are several 9 pin connectors with white wires. These are the ground wires which connect to the metal housing the transformer panel. Often the part of the connector with the male pins bolted to the side of the metal panel crack. At minimum these should be removed, inspected, and resoldered. If one pin's solder joint cracks, the wire that connects to that pin will lose its ground path! This is a very bad thing. To really bullet-proof this design, all the ground wires can be shorted together BEFORE going to this connector. That way if one pin cracks, it's no big deal, as the other pins take the load.

   On Sys80B another thing that must be done is to resolder the .156" J1 and J2 connector male header pins on the power supply board. There are only two connectors on this board, and it is very common for these to have cracked solder joints around the pins (giving intermittent power/ground paths).

   And on Sys80B power supply, while you're resoldering the header pins, attach a ground wire to the bottom J1 pins 1,2 (ground). Run this wire to the yellow ground plane bolt at the bottom right side of the backbox.

Step 3 on Sys80b, resolder the power supply header pins and add a ground wire to J1 pins 1,2.

Step 3 On sys80B, find the 9 pin ground plugs on the side of the transformer metal panel. Remove the connectors, and then remove the two 1/4" hex bolts that hold the male pins to the side of the transformer panel. On the back side of these small connector PCBs, resolder the pins as the solder joints like to crack.

Here's the System80b ground PCB removed from the side of the transformer panel. Cracked solder joints can be seen here (resolder these).

In the future to prevent a single cracked solder joint pin from effecting a ground, all the ground wires can be tied together before the connector.

Another way of solving the ground problem on a system80B transformer frame. The original connectors (at bottom) were cut off and replaced with spade connectors. These these were bolted directly to the transformer frame.pic by j.p.

Another version of the system80B transformer. This version uses .156" molex connector pins to attact the ground wires to the transformer frame. This version should be treated like the above version, where all male pins are check for cracked solder joints (and possibly resoldered).

Yet another version of the system80B transformer. This version is pretty good, just make sure all those individual ground connectors on the side of the transformer frame are tight.

And another version of the system80B transformer. This version is really good, as all those individual ground connections are soldered to a terminal strip on the side of the transformer frame.

4. STEP 4: On all sys80,sys80a,sys80b games, on the connector CPU A1-J4 to Driver board A3-J1 (that goes from the Driver board to the CPU board), double-up the Ground and +5 volt lines (note on some system80b games this may have been done by the factory). Order Molex terminal series 4366, part #08-03-0304 (for 18 gauge wire). Crimp and/or solder the new pins to some wire (see the following section on connectors for how to do this).
   • Insert two pins and wires into the A3-J1 Driver board connector at the back side, far right (as facing the installed boards).
   • Insert the other two pins and wires into the A1-J4 CPU board connector at the front side, far right (as facing the installed boards).
   • Splice the two outside wires from A1-J4 and A3-J1 together (ground).
   • Splice the other two inside wires from A1-J4 and A3-J1 together (+5 volts DC).
   Now the pins are doubled up and have reliable +5 volts DC and ground contacts from the CPU board to the Driver board. One can also buy a new connector that already has this modification done. They are gold plated and have two +5 and two ground pins. This is available from Docent Electronics at 937-253-2768, $25.00 plus shipping.

   Note: Double sided connectors (A3-J3 in this case) use numbers for the pins on the front (component) side of the board, and letters for the pins on the back (solder) side of the board. Some letters are not used because they look too much like numbers. These include: G, I, O, Q. If more than 22 pins are used, a "bar" is designated over the repeated letters. For example, pin 23 (where pin 22 = Z) on the back side of the board would be designated as "/A".

Docent Electronic's CPU to Driver board connector for system80 games. The ground and +5 volt lines are already doubled-up on this brand new connector.

5. STEP 5: Run a ground wire directly to the Solenoid Driver board. Just below chip Z10 on the solenoid driver board there is a large, thick trace, which connectos to Z10, Z11, Z7, Z5, Z3, Z1 pin 7. Scrape the solder mask from this trace and attach a 18" wire. Be careful not to short the wire to the row of resistors beneath this large trace, or the smaller trace above it (which connects to Z2 pin 11). Alternatively there is a vertically mounted capacitor on the upper right side of the driver board - connect the ground wire to the lower lead of this cap. On the other end of the wire attach a "fork" connector. Connect the fork connector to the metal frame of the power supply. If doing this on a system80b game, connect the ground wire to the ground plane bolt in the upper right corner of the backbox.

Step 5. Attaching a ground wire to the solenoid driver board below Z10. Picture by J.Robertson.

6. STEP 6: If the game has an Auxiliary Lamp Driver board (Haunted House, Black Hole, Volcano, Mars God of War, etc.), run a ground wire to this lamp board. The Auxiliary Lamp board is used for the marquee lights in the backbox of a handful of system80 games. If the ground is unreliable to this board, the score displays can flicker and act strange. Scrape the green solder mask from the large circuit board trace between the lower left chip and the MPS-U45 transistors at the edge of the board. Solder a wire to this trace, then continue the wire to the metal power supply frame to complete the ground path.

Step 7. Attaching a ground wire to the chaser light board as used on Haunted House, Black Hole, and some other system80 games. Picture by J.Robertson.

7. STEP 7: If the game has a sound/speech power supply board, add a ground wire to this. On the back (solder side) of the board there is a large trace running around the edge of the board. Scrape the solder mask from this trace and attach an 18" piece of wire to this trace. Then continue the wire to the metal power supply frame to complete the ground path.

Step 8. Attaching a ground wire to the sound/speech power supply board as used on some system80 games. Picture by J.Robertson.

8. STEP 8 (Sys80B only). The ground wire going to the power supply module connector J1 pin 2 (bottom conector, white wire) needs a second wire attached to this pin for an added ground. Remove the J1 pin 2 from the connector housing, and crimp on a new .156" Trifurcon connector pin, adding a second wire to this pin. Then run this wire to the upper right corner of the backbox and attach to the ground plane screw.

At this point, the mandatory grounding modifications are done.

System80B Raven backbox with the mandatory ground mods and remote battery pack installed.

Optional Ground Modifications Steps.

The grounding modifications can be taken one step further. The following will tie all grounds on the driver board together, except for the solenoid ground (which will be isolated to protect the circuit boards from solenoid feedback to the logic ground).

If you do not have much circuit board repair experence, it may be a good idea to skip these steps. Though the following solves some driver board ground problems, these mods are not nearly as important as the above "manadatory" cabinet ground to circuit board ground modifications.

IMPORTANT: a note about "Wire Wrap" used in this procedure.
Through out this procedure, small 30 gauge blue wire can be seen, which is used for all ground modifications. This wire is known as "wire wrap". I used this type of wire in the pictures below because it's easy to work with (and does "clean" modifications), and it shows up great in the pictures. BUT in reality, it is probably too small for these ground modifications! I highly suggest using thicker wire (such as cut off resistor leads), or double/triple up the wire wrap on each of the connections shown below. There is a potential for up to 8 amps to go through these added connections. Wire wrap will vaporize at about 3 amps.

Note: for the fixes on the driver board I have the board positioned so the "bottom" is the edge with the J4 edge connector. Likewise for the CPU board, the board is positioned as it would be installed in the game with connectors J4, J5, J6 at the "bottom".

1. Remove the three metal cased power transistors Q58, Q62, and Q64 (2N3055) from the driver board:
   • Each transistor has two screws. Remove these screws.
   • De-solder the two transistor leads for each of the three power transistors.
   • Notice the thin mica insulator for all three transistors. Cut the mica insulator so the bottom screw (the screw the leads are closest to) is not covered by the mica.
   • On the component side of the driver board, tin the bottom screw contacts for all three transistors. Note this is the contact that leads to ground (the upper contact has no traces attached to it).
   • Test the removed transistors (2N3055). Set the DMM to the "diode" setting. Put the black lead on the metal case of the 2N3055, and the red lead on each leg. A reading of .4 to .6 for one leg, and no reading for the other leg should be seen. Now put the red lead on the "base" lead (see picture below) of the transistor. Put the black lead on the other 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).
   • Re-assemble the transistors and make sure to crank the screws down tight. Resolder the transistor leads to the board.
   • Check the three BIG 1 watt 9.1 ohm resistors connecting to the 2n3055 transistor. These should be 9 or 10 ohms in circuit.
   The metal case of the power transistors should now make excellent contact to ground.

Step 1: A removed driver board transistor from Q58 with the mica insulator modified. Also the bottom mounting hole has been tinned with solder for better contact on the driver board.

Steps 2 on the driver board.

2. On the component side of the driver board at connector J5 pin 3, there is a via (plated through hole). There is also another via just under transistor Q59's left most leg. Connect these two vias together with wire.

Steps 3, 4 at driver board connector J4.

3. On the solder side of the driver board, note the vias at connector J4 (bottom right solder side of board). From the solder side with connector J4 at the bottom, pins are numbered from the left (note there is a "1" screened on the board at pin 1). At J4 pins 9,10,11,14 (solenoid grounds) scrape the green solder mask from the board from the bottom most trace immediately above the pins - this trace goes to J4 pin 15, which is ground. Run some wire through the pins 9,10,11,14 vias and solder them all to this ground trace (pin 15). Note tying J4 pin 5 (lamp ground) to this solenoid ground trace was removed from this step 12/18/03 because tying the lamp ground to the solenoid ground is not correct.
4. On the solder side of the driver board, locate J4 pin 5 (lamp ground). Solder a jumper from J4 pin 5 (lamp ground) to the via that is 3/4" above J4 pin 6 (another lamp ground which attaches to J3 pin C). This jumper attaches two lamp grounds together.

Step 5 on the driver board.

5. On the solder side of the driver board, solder a wire from the trace that connects to the right most pin (emitter) of transistor Q43, to the trace that connects to the bottom most pin (emitter) of transistor Q51. If either of these transistors are replaced in the future, make sure to maintain this jump.

Steps 6, 7, 8, 9 driver board solder side view.

6. On the solder side of the driver board along the lower edge (about 3" from the left and just above connector J3), there is a large "Y" or "T" shaped trace. This trace originates at pin U (letters are used to label pins on the solder side for double sided connectors; 4th pin from the left) of connector J3, and is directly above the label "J3" on the board. Scrap the green solder mask from this thick trace, just below transistor Q23. Now connect the lower pin (emitter) of Q23 to this thick trace. If this transistor is replaced in the future, make sure to maintain this jump.
7. On the solder side of the driver board, solder a wire from the right most pin (emitter) of transistor Q9, and connect it to the thick "Y" trace. If this transistor is replaced in the future, make sure to maintain this jump.
8. On the solder side of the driver board, solder another wire to the thick "Y" trace just soldered in the previous step. Just to the right of this, scrape the green solder mask off the two traces that connect to pins 9 and pins 11 of the J3 connector (as counted from the left). Connect the other end of the wire to both of these traces.
9. On the solder side of the driver board, find transistor Q25. Scrape the green solder mask on the trace just below the Q25 emitter (lowest pin closest to the bottom edge connectors). Connect Q25's emitter to this trace. Usually there is enough lead on the transistor to use this as a jumper to the ground trace. If this transistor is replaced in the future, make sure to maintain this jump.

Step 10 on the driver board.

10. On the component side of the driver board, cut the large trace in the lower left corner that goes to connector J5 pin 15, and goes around the large transistor Q64 and the "hole" in the circuit board (this was a design error). NOTE: most driver board test fixtures will *not* work after this trace is cut! So this modification should be reversed if this driver board is sent in for repair.

Step 11 on the driver board.

11. On the solder side of the driver board, find the bottom pin (emitter) of transistor Q56. Using wire, connect a jumper to the via that is 1/2 inch below and to the left of Q56. Continue this jumper to the large trace that connects to the bottom pin of Q54.

12. Examine the rest of the driver board: Any unsoldered vias should be soldered. Any puckered vias should be re-soldered. Examine the soldered components too. Any component leads that do not cover their pad should be re-soldered. Any cut solder meniscus (mounds) should be re-soldered also.

The optional driver board modification are now complete.

Score Display Grounds (flickering displays).
There is yet another ground issue that needs to be addressed, and this relates to the score displays in system80 games. Often the score displays will flicker. As John Robertson has documented, it turns out that the common return path for the displays comes in two separate lines back to the power supply. Making a simple short between the two pairs of display ground wires solves intermittent pin connection failures on the score displays. This simple fix often solves score display flickering. Also on games with a playfield mounted score display (Haunted House, Black Hole, etc), the ground to these score displays can be intermittent also, causing these displays to flicker.

System80 Games with Auxiliary Lamp Driver Boards.
Another problem with score displays exists on games with auxiliary lamp driver boards (like on Haunted House and Black Hole). The auxiliary lamp driver board controls the lighting effects in the backglass. Sometimes the score displays can be seen flickering to the beat of the backbox lighting affects (which are controlled by the Auxiliary Lamp driver board). Unplugging the Auxiliary Lamp driver board can show the displays no longer flash or flicker. This can be especially a problem with the score displays mounted in close proximity to the Auxiliary Lamp driver board on Haunted House. The solution to this problem is the run an additional ground path to the Auxiliary Lamp driver board, using the updated ground path enforced in the above sections. Also check the back of the Auxiliary Lamp driver board for cold or open solder joints.

Random Pop Bumper Problems (Bad Pop Bumper Grounds).
Yet another ground issue on many system80 games is the ground path for the pop bumper driver boards. Often pop bumpers will work intermittently, or will fire when a ball is no where near the pop bumper in question. This problem is due to a bad ground path to the under-the-playfield pop bumper driver boards. There is but one pin on the MPU board that brings the ground path to the pop bumper boards. If this one pin is intermittent, pop bumper problems will happen. Again the solution is to "double up" the ground path from the pop bumper driver boards to the grounds reinforced above in the backbox.

Replace the Electrolytic Capacitors on the MPU and Driver boards.
Another "good idea" is to replace the (probably) dried-out electrolytic capactors on the MPU and driver boards. This includes C1 on both the CPU and driver board (used for power supply decoupling), and C36 on the MPU board (used for the initial power on delay).

One of the biggest problems with System80 games are the connectors. Gottlieb used card-edge style connectors for most of their circuit boards, and over time, these have proved to be less reliable than the header-pin style connectors used by other pinball manufacturers. Add to this battery corrosion issues, and the connectors become Gottlieb's weak point for reliability. Because of this, it is highly recommended that at minimum all the bottom edge CPU board connector pins and power supply pins be replaced. In addition many driver board connectors will often need to be replaced too.

Insulation Displacement Connectors (IDC) Card Edge Connectors.
All Gottlieb System 80 games use card edge Insulation Displacement Connectors (IDC). IDC means that the connector has a "V top" metal pin that a wire is pushed into. This "V" cuts the insulation allowing the pin to make contact with the wire. The IDC style of connector is still used by most pinball manufacturers today. They allow fast and easy wire connection without any soldering. There are also some crimped style connector pins in system80 games. This is a much better design than IDC connector pins because the wires attach better to the pins.

All pinball manufacturers have stopped using card edge connectors, as used on System 80 games, in favor of header pin connectors. Header pin connectors have the advantage of allowing multiple wipers per pin, less pin fatigue, and easier replacement (on both the board and connector housing). This gives better long-term reliability.

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 actually 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 system80 games, but not all):

• A1 = CPU (controller) board.
• A2 = Power supply board.
• A3 = Driver board.
• A4 = Score display boards.
• A5 = Status digit display board (4 digits).
• A6 = Sound/speech board.
• A7 = Sound/speech power supply board.
• A8 = Pop bumper driver board(s).
• A11 = Auxiliary lamp driver board.

Battery Corrosion and Connectors.
If there are battery corrosion problems, these card edge IDC connectors just magnify the problem (and sometimes allow the leaking battery electrolyte to travel thru the connectors to other boards!). Inspect the connectors and board edge "fingers". If corrosion is visible on the board, clean the edge fingers by lightly sanding the corrosion with 220 grit sand paper to remove it. 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 99% 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-tin the connector fingers with solder. Also the connector housing connector pins should be replaced. At minimum, clean these connectors with alcohol and a Q-tip. If the connector pins have any corrosion (the pins are not shiny, but have a dull grey or green appearance), they must be replaced.

If you want to "test" the general health of a game's connectors, try this. Remove the connector that goes between the bottom edge of the CPU board and the top edge of the driver board. (This is a double sided inter-board connector.) Bang this connector on a (clean) workbench. Give it a good "bang" a few times, hitting the black plastic end on the workbench. Are there ANY pieces or junk seen on the workbench from this banging? If so, your game has failed the "bang" connector test! You will need to repin this connector, and probably all the connectors along the bottom edge of the CPU board.

An "official" Molex card edge pin extraction tool. A far better Molex extractor is part number 11-03-0016 (this tool is part number 11-01-0014).

Connector Parts and Tools needed:
• Molex card edge pin extraction tool, part# 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 connector pins. See below.
• Molex connector bodies (the plastic part that holds the pins). Optional, as sometime the original connector body can be reused. See below.

CPU Board Connector Types.
Here is a list of the connectors used on the system80 CPU board. The CPU board connectors are listed because these are the ones affect by battery corrosion the most. The connectors on the power supply, sound board and driver board are much less affect by corrosion, and hence may not need to be replaced.

• A1-J1: Edge connector, crimp pin style, 5 pin, single sided, 18 guage wire. Main power connector from power supply, upper left side of CPU board.
• A1-J2: Edge connector, IDC, 24 pin, single sided connector. Score display segments, right side of CPU board.
• A1-J3: Edge connector, IDC, 17 pin, single sided connector. Score display digit strobes, right side of CPU board.
• A1-J4 (to A3-J1): Edge connector, crimp pin style, 24 pin (per side), 48 pins total, double sided connector. CPU to driver board connector (solenoid, sound and lamp controls), bottom side of CPU and top side of Driver boards.
• A1-J5: Edge connector, IDC, 10 pin, single sided connector. Switch matrix strobes (to the playfield), bottom side of CPU board.
• A1-J6: Edge connector, IDC, 19 pin, single sided connector. Switch matrix returns (to the playfield), bottom side of CPU board.

Location of the connectors is important. Since the battery is on the left side of the CPU board, the CPU connectors around and below the battery often need to be replaced. This includes CPU connectors J1 (upper left edge), and J4, J5, J6 (bottom edge of CPU board).

Crimp-on Replacment Connector Housings and Pins.
On the CPU board, the non-IDC connectors can have new connector pins installed into the current plastic connector housing. This includes CPU connector J1 and J4 only.

Also, the remaining CPU IDC connectors (J2, J3, J5, J6) should ideally be replaced in their entirety, including the plastic housing, and converted to crimp-on style pins. Unfortunately, these card edge crimp-on connectors housings are very difficult to find. Therefore, crimp-on style pins can be installed into the old IDC connector housings, with some minor modifications.

Connector (terminal) pins will be required, but Molex connector pins are somewhat difficult to order, as there are so many different varieties. Note the "chain" variety are not wanted, unless the "loose" variety is not available (the chain type may be cut with a sharp pair of scissors). 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).

Molex Replacement Connectors for System80 CPU
Connector	Type	Housing Series	Housing Part#	Wire Gauge	Pin Series	Pin Part#
A1-J1* main power	5 Pin one sided	2574	09-01-7051	18 - 20 22 - 26	2478 2578	08-52-0072 08-50-0134
A1-J2 displays	24 Pin one sided	2574	09-01-7241	18 - 20 22 - 26	2478 2578	08-52-0072 08-50-0134
A1-J3 displays	17 Pin one sided	2574	09-01-7171	18 - 20 22 - 26	2478 2578	08-52-0072 08-50-0134
A1-J4*/A3-J1 CPU/Driver PCB	48 Pin two sided	4338	09-50-6245	18 - 20 22 - 26	4366 4573	08-03-0304 08-03-0306
A1-J5* Switch Matrix	10 Pin one sided	2574	09-01-7101	18 - 20 22 - 26	2478 2578	08-52-0072 08-50-0134
A1-J6* Switch Matrix	19 Pin one sided	2574	09-01-7191	18 - 20 22 - 26	2478 2578	08-52-0072 08-50-0134

* Connectors that often need to be replaced.

There is a double sided A1-J4/A3-J1 connector, that goes from the CPU board to the driver board. The plastic housing is Molex series 4338. The 48 pin (24 per side) part number is Molex part number 09-50-6245 (with mounting flange). If you use a high-powered magnifying glass you can read the part number stamped into the rear of the housing along one edge. The housing accepts series 4366 terminals pins (or 4573 series). Gottlieb uses just the 4366 series of pins (designed for 18-20 guage) for all wires, regardless of the wire gauge (18 gauge is used in high stress applications, and 22 gauge is used in switch and lamp applications).

Regarding the single sided plastic housings, Molex sells both "with flange" and "without flange" versions. The "with flange" version is what to buy, as the "without flange" versions are special order only. But either style will work. The flange is basically some surrounding plastics allowing the connector to be bolted to a circuit board.

All other single sided connectors (except A1-J1) should ideally be replaced in their entirety. The single edge connectors can be replaced with the Molex 2574 series crimp-on plastic housing, using 2478 (or 2578) pins (depending on the wire guage). Unfortunately these plastic connector housings are very hard to find. But the good news is we can use the current IDC plastic housing with the 2478 crimp-on pins.

Connector Parts Typically Needed (order this stuff!)
On many System 80 games, these are the parts typically need (applies largely to Black Hole/Haunted House era games). That is, these are the parts needed to fix the CPU board's J1, J5, J6 connectors, and the CPU/Driver boards' A1-J4/A3-J1. Remember, the plastic connector housings on the CPU board at J1 and J4 can be reused (but any others need to be replaced, because they will be converted from IDC to crimp-on pins). Quantities are typical for doing one game.

• (35) Molex 08-52-0072 crimp-on pins (for single sided connectors).
• (100) Molex 08-03-0304 crimp-on pins (for double sided connectors).
• (1) Molex 09-01-7101 plastic connector housing, 10 pins (J5), optional.
• (1) Molex 09-01-7191 plastic connector housing, 19 pins (J6), optional.

The single sided connector pins 08-52-0072 are available from digikey.com, part number WM2302-ND. The double sided connector pins 08-03-0304 are available from avnetmarshall.com using the Molex part number. Both of the above pins are also available from ttiinc.com (800-225-5884) using Molex part number. Note both TTI and Avnet have 500 part minimums (Digikey will sell smaller quantities). The plastic connector housings I do not have a source, but the current IDC housings can be used with the crimp-on pins.

If doing all the connectors on the CPU board, the following parts will also be needed (parts needed to do the display connectors A1-J2, A1-J3 on the right side of the CPU board):

• (45) Molex 08-52-0072 crimp-on pins (for single sided connectors).
• (1) Molex 09-01-7171 plastic connector housing, 17 pins (J3), optional.
• (1) Molex 09-01-7241 plastic connector housing, 24 pins (J2), optional.

If doing the connectors on the Driver board (in addition to the already mentioned A3-J1 connector), here are those parts typically needed. This will replace the solenoid drive connectors A3-J4, J5, J6. The solenoid drive connectors are the ones the cause the most game problems when they fail (note connector J5 also handles some sound). The remaining driver board connectors (J2, J3) are lamp and sound connectors, and rarely need replaced (though connector J3 does also handle some relays, including the game over, tilt and coin lockout relays). The good news about A3-J3 is it's a double sided, 50 pin, crimp-on style connector. So its plastic housing can be easily reused, and just the pins replaced with Molex 08-03-0304 pins.

• (30) Molex 08-52-0072 crimp-on pins (for single sided connectors).
• (100) Molex 08-03-0304 crimp-on pins (for double sided connectors).
• (1) Molex 09-01-7101 plastic connector housing, 10 pins (J2), optional.
• (1) Molex 09-01-7151 plastic connector housing, 15 pins (J4), optional.
• (1) Molex 09-01-7081 plastic connector housing, 8 pins (J5), optional.
• (1) Molex 09-01-6041 plastic connector housing, 4 pins (J6), optional.

The Connector between the CPU and Driver board.
This double sided connector often has corroded pins because the CPU side of the connector is near the battery. If the double sided connector pins can not be found easily to repair the original connector, a new replacement can be purchased from Docent Electronics (937-253-2763) for $25. Docent also added the additional ground and +5 wires to this connector, as described in the previous Grounding Modification section above.

Crimp-On Connector Pin Instructions.
The following documents were drawn by Bob Ellingson. It explains the removal of old connector pins, and crimping on new ones.

To install new connector pins from the strip molex pins #2478, note these diagrams.

The best way to attach the new pins is with a Molex WHT-1921 or Amp 725 crimping tool (but Radio Shack also sells a decent crimping tool). Done properly, a good tight crimping connection is better than a soldered connection (and takes a lot less time!). The crimp is done in two steps. First crimp the bare wire end in the first saddle (the saddle closest to the wiper). Second, crimp the insulation in the second saddle.

To reassemble the connector, just push the new pins into the back of the old plastic housing, until the latch "clicks". Make sure to install the pin with the wiper towards the inside!

Re-using the Current IDC Connector Housings with Crimp-On Pins.
YES the IDC plastic connector housing can be re-used with crimp-on pins. The hardest part about doing this is removing the old IDC pins from the plastic housing. What follows are the steps to do this. Just do one pin at a time, so the wires/pins can not easily be mixed up.

Step One.
Acquire the tools needed for this. This includes a smaller jewelers screwdriver, needle nose pliers, and a crimper.

Step Two.
Using a small jeweler's screw driver, bend the pin's notch permanently down. No need to be gentle here, push it and bend it down.

Step Three.
Pull the exiting wire from the IDC connector housing. If lucky, the IDC pin should come out with the wire. If not, use a pair of needle nose pliers to pull the IDC pin out of the housing. It should come out fairly easy.

Removing the IDC pin with needle nose pliers after the "notch" was bent out of the way with a jeweler's screwdriver (the blue circle shows where the notch was bent down).

Step Four.
Cut the existing wire back about a 1/4", to remove the portion of the wire that was formerly used in the IDC pin. Then crimp a new Molex 08-52-0072 pin onto the old wire (see crimping instructions above).

Getting ready to install the new crimp-on pin into the housing.

Step Five.
Insert the new crimp-on pin into the housing. The crimp-on pin should fit right into the old IDC plastic housing, without resistance. If it does not go in easily, you are inserting the pin incorrectly into the plastic housing. Another possibility is the crimp-on pin may have too much material on the sides of the pin (where the pin was cut from the factory out of the reel strips), making the pin's "wings" a tad too wide. This seems to happens to about 10% of the crimp-on pins I use. To fix this, I just gently file the sides of the pin.

The new crimp-on wire and pin installed in the old IDC plastic housing.

This procedure can now be repeated for the next pin.

Removing Pins from Gottlieb Double-Side Connectors.
Removing connectors pins from double sided connectors is fairly easy, if these steps are used. New replacement Molex 08-03-0304 crimp-on pins should be used.

First bend the pin inward on both sides, one at a time, using needle nose pliers.

This picture shows both pins bent inward. Don't try and do just one pin, as you will surely bend the opposite pin too.

Next insert the Molex pin removal tool between the plastic housing and the metal pin. Gently pull the wire connecting to the pin, and the pin should pull out of the plastic housing. Next do the opposite pin, but be careful not to mix up the two pins!

Replacement EDAC Connectors.
The above connectors can also be bought using the EDAC number. These connectors have solder lug (instead of crimp pins). But note that only the 10 pin connector can be purchased with the correct number of pins. For example, one can't buy a 24 pin single sided connector; instead buy a 25 pin double sided connector and use it as-is, or cut it. Though this is not a recommended way to replace connectors, here is the EDAC information:
• (1) 5 pin, single sided connector (A1-J1). EDAC #307-012-500-202
• (1) 24 pin, single sided connector (A1-J2). EDAC #307-050-500-202
• (1) 17 pin, single sided connector (A1-J3). EDAC #306-018-500-102
• (1) 24 pin (per side), 48 pins total, double sided connector (A1-J4 to A3-J1). EDAC #307-050-500-202
• (1) 10 pin, single sided connector (A1-J5). EDAC #306-010-500-102
• (1) 19 pin, single sided connector (A1-J6). EDAC #306-022-500-102

Making New Connectors from Video Game Harnesses.
If not buying new pins, one can make a new connector from JAMMA video game harness connector (about $15 new each). These 28 pin double sided connectors can be cut to length. I find this better than using the EDAC solder lug connectors, as the pins are replaceable. Here are the instructions for modifying a JAMMA video game harness in a system80 game:

• First a IDC pin removal tool is needed. A small jeweler's screwdriver can also be used. Or take a 5 watt resistor, and cut one lead to 3/8" long (five watt resistors work nice because the resistor is like a big "handle" to grab).
• Insert the 3/8" long lead of the resistor or the jeweler's screwdriver into the top (where the card edge would go) of the new JAMMA connector, between the pin and the plastic wall (see the drawings above). It's a tight fit, but it will go.
• Gently pull the wire lead, and the pin should come out. Note: unfortunately this technique doesn't work on the original IDC's in many System 80 games. If it did, we could just replace the pins and not the entire connector! I haven't found a way to get the pins out of the original System 80 connectors if they are damaged.
• Repeat this, removing enough wires until the connector is the size desired.
• Saw the end off the connector (a bandsaw works nicely for this) and save it.
• Saw the empty pins off and discard.
• On a belt sander, flatten and smooth the cut edges on the connect and the cut off end.
• Super glue the end back onto the connector, making it the length desired. Test the connector on the board before gluing to make sure the ends are trimmed to the proper length.
• To make a single sided connector from a double sided one, just cut the wire from the unused side. Or remove all the unwanted pins and wires using the above removal method.
• When re-soldering the connectors, use heat-shrink tubing for a good, clean look.

Circuit Board Card Edge Fingers Destroyed.
When the card edge fingers on the board are destroyed and unusable, the single-sided ID connectors can be replaced with the Molex .110" header pin style connectors. This can be done by drilling 1/16" holes through the edge connector fingers on the board, and inserting the molex pins thru these hole from the non-fingered side of the board (at a right angle). Then the plastic header pin guide can be super glued to the non-finger side of the circuit board. Then on the other side of the board, the pins can be soldered to the edge connector's fingers (if possible). Note this can only be done to the single-side IDC's (there is only one double-sided IDC on the CPU board). I don't recommend this fix, but if there is no choice, it may be usable. Cleaning the existing connectors (or replacing them with the same kind) is a much better idea.

PBDB Introduction.
Pop Bumper Driver Boards (PBDB) are unique to Gottlieb System80 games. (They were not used on Gottlieb System1 pinball games.) The driver board has a limited number of driver transistors for solenoids. Using the PBDB allowed Gottlieb to increase the number of controlled coils. PBDB driven coils are good thing - a problem on System1 pop bumpers was if a pop bumper skirt was mis-adjusted, the coil could lock on and burn. The System80 PBDB does not allow this to happen because it is a "one shot" board. That is, if the switch input locks on, the PBDB will only pulse the driven coil one time for a set duration, and it will not lock-on the coil. This prevents burnt coils and gives consistent "kicks" from the pop bumper.

When the ball hits the skirt on the Pop Bumper, the skirt closes a switch. This switch connects to the Pop Bumper Driver Board (PBDB) pin 4 and logic ground, which triggers the PBDB to momentarily ("one shot") ground the solenoid coil and energize the Pop Bumper. There is no CPU or driver board involved. There is however a second switch which closes on the pop bumper assembly as the coil energizes. This goes back to the CPU board through the switch matrix and says "score points" (hence this second switch is for scoring points only). A similar approach was taken by Williams for system3-9 (but Williams had their PBDB built into the driver board itself, and unfortunately the Williams version was not "one shot").

Diagnosing a Non-Working Pop Bumper.
Before doing any modification to a Pop Bumper Driver Board (PBDB), the best approach is to get it working. Here is a list of things to check:

• First of course check the pop bumper fuse. Yes every coil driven by a PBDB will have a fuse! This fuse is mounted on the bottom side of the playfield. With the game off remove the fuse and check it with a DMM set to continuity. Make sure you are checking the correct fuse too (sometimes there are lots of coil fuses mounted under the playfield).
• Measure the voltage at the coil. With the game on and a game started, check for 25 to 40 volts DC at *both* lugs of the coil in question. If voltage is seen at just one lug, the coil is bad. Voltage at neither lug means the pop bumper fuse is dead. (Also note if the game-over relay is manually held in, power is supplied to the pop bumper.)
• Test the coil. With the game on and a game started, using an alligator jumper lead, connect one end to the ground strap in the bottom of the game. Momentarily touch the other end to the NON-BANDED diode lug of the coil in question. The coil should fire. If not there is no power to the coil, or the coil itself is bad.
• Measure 5 volts at the PBDB. With the game on and a game started, Put a DMM on pins 5 and 6 of the PBDB (reference pin 3 is the "key" pin). There should be 4.8 to 5.2 volts DC. If not, put the black lead on the bottom panel ground strap (where all the green wires go) and the red lead on the PBDB pin 5. Is there 5 volts now? If so the ground connection to the PBDB has failed. Ground comes from the CPU board connector A1J6 pin 9, so check this connector. Often if ground is missing to the PBDB, the pop bumper coil will locked-on (assuming the pop bumper coil fuse is good). The 5 volt power comes from the CPU board connector A1J6 pin 18. Check this connector too! And if you are modifying the PBDB, add the +5 volt LED mod shown below, which helps identify problems like this quickly.
• Test the coil-to-PBDB connection and power by jumping the PBDB pin 1 and pin 2. If the connection is good, the coil should fire. A spark may happen when you do this, and only jump these two pin momentarily or the coil may burn. If the coil does not fire, there is a wiring problem between the coil and the PBDB.
• Test the PBDB itself by jumping PBDB pin 4 and pin 6. This is simulating the pop bumper skirt switch closure. If the coil fires, the PBDB is fine, and there is just a switch or wiring problem. Check the pop bumper skirt switch wiring for continuity with one wire going to PBDB pin 4 (trigger), and the other to PBDB pin 6 (logic ground).
• If everything checks out so far but the pop bumper coil does not work, the PBDB itself is dead.

Common PBDB Problems.
If the Pop Bumper Driver Board (PBDB) is dead, here's some things to check:

• Cracked connector header pins. This is very common, as the solder joints like to crack around the male header pins on the PBDB. The pin that seems to crack most often is the pin that connects to the metal case of transistor Q1 (pin 1). If this pin is not making contact, this can cause the pop bumper coil to lock on. Resolder these male header pins.
• Broken traces. Because the PBDB is a single sided board, broken traces around components is often seen.
• Transistor Q1 (2N6057/2N6059) has failed. This is very common. Test the transistor with a DMM set to the diode function - Black DMM lead on either transistor case screw, red DMM lead on either transistor lead and .4 to .6 volts should be seen. A bad Q1 can cause the PBDB to not work at all, or to lock on its associated coil.
• Electrolytic capacitor C4 (near the male header pins) has gone open.
• Either or both TTL chips (74LS121 and 74LS16) have failed.
• If the pop bumper in question works sparatically, try replacing PBDB capacitor C4 (47 mfd 10 volts).

More PBDB Repair Ideas.
As for fixing a broken PBDB, there are some short cuts to this procedure. For example, a kit can be purchased from Big Daddy which replaces all the parts on the board with new parts. That is certainly one approach.

But keep in mind that non-working PBDBs can be related to other things. For example, if the board is not getting 5 volts at pin 5, it just won't work! The 5 volts for the PBDB comes from the CPU board connector A1J6 pin 18, which just happens to be beneath the battery. So any battery corrosion could disable the connector fingers or the connector pins.

Likewise there are *two* different grounds supplied to the PBDB. One is the solenoid ground bus (comes in at pin 1 and goes back to the coil at pin 2). The other is the "DC ground" (pin 6, which is the logic ground). The DC Ground is again supplied by the CPU board connector A1J6 pin 9. If 5 volts is present to the PBDB, but the DC Ground is not, the pop bumpers will lock on as soon as a game is started! A bad pin or connector finger at CPU J6 is usually the culprit.

If the Pop Bumper Driver Board's fuse blows every time a game is started (and the pop bumper coil is 2.5 ohms or greater and the 1N4004 coil diode is new), suspect the two chips on the pop bumper driver board. The 74LS121 and/or the 74LS16 can have an internal short which will cause the pop bumper's 2amp slo-blo fuse to fail. This can be tested by using a DMM set to the diode function. Put the black lead on the chip's +5 volt power leg, and test each other leg with the red DMM lead. A reading of .4 to .6 should be seen for each chip leg (except for the chip ground leg).

This repair is mandatory on all early System 80 games (Haunted House and before). This modification corrects a design error. Gottlieb recognized the problem, issued a technical service bulletin, and fixed this error. But many games had been sold without this fix. All pop bumper boards need to be checked to see if this factory upgrade had been made. To quickly identify this modification look for:

2 diodes (CR1 & CR2) = original (bad) design
1 diode/1 jumper (CR2 & jumper) = modified/upgraded.

Un-modified pop bumper driver board (PBDB)

Modified pop bumper driver board (PBDB). Note the replacement of one diode with a jumper, the new capacitor (installed in reverse) below it, and an added capacitor to the reversed side of the board (show at the right). Cap C4 should always be replaced too, and the male connector header pins resoldered.

Parts Needed (for each pop bumper board):
• (1) 4.7 mfd 10 volt capacitor, axial or radial, for C3.
• (1) 4.7 mfd 10 volt capacitor, radial (both leads out one end), added to pins 4/5 of connector.
• (1) 47 mfd 10 volt capacitor (or even 100 or 150 or 200 mfd), for C4.
• (1) 1 mfd, 100 volt capacitor non-polarized (optional), for C1.
• (1) 10k ohm resistor 1/4 watt (optional), for R1.

Modification:

• Note the negative lead position of capacitor C3. Mark the position of the negative lead with a pen right on the component side of the board (the lead towards the center of the board).
• Remove capacitor C3.
• Insert a new 4.7 mfd capacitor in the reverse direction. That is, the positive lead of the capacitor is now towards the center of the board (and connects to pin 10 of the 74LS121). Cross the negative mark made on the board with a pen (to make it positive) to avoid future confusion. Note there are two pads for the positive lead of the capacitor. Gottlieb did this so one can install either an axial or radial style capacitor. Just make sure to solder the unused pad so it's closed.

Note the two pads used for mounting the positive lead of capacitor C3. Gottlieb did this so one could use either style of capacitor (axial or radial). The unused pad should be soldered over (which hasn't been done here yet). Also note this PBDB has been modified to add a LED for a visual indication of +5 volts to the PBDB.

Add a 4.7 mfd radial cap to header pins 4/5 to prevent "noise".

• Remove diode CR1. Replace with a jumper wire.
• Remove capacitor C4 and replace this 47 mfd capacitor with a new 47 mfd or higher (100 mfd to 200 mfd) 10 volt capacitor.
• Re-solder the connector header pins on the board. These solder joints often crack from plugging and unplugging the molex connector on the board. VERY important!
• Add an electrolytic 4.7 mfd 16 volt capacitor to pins 4 and 5 of the male header pins (negative to pin 4, add on solder side of PBDB). This cap prevents "noise" from causing pop bumpers to fire sporatically.
• Make sure Q1 is making good contact to the pcb. Remove the one screw on Q1 (the large metal cased power transistor) that has a trace connected to it. Re-solder and tin this hole lug on the board so it makes good contact to the screw and metal case of the transistor. Re-assemble and tighten the screws.
• Test the large metal Q1 power transistor (2N6057/2N6059) installed in the pop bumper driver board. Set the DMM to the "diode" setting. Then put the black lead on the bottom attachment screw of the transistor (which is connected to the metal case of the 2N6057/2N6059), and the red lead on each leg. A reading of .4 to .6 for each transistor leg should be seen. Anything else and this transistor is bad.

Pop Bumper Driver Board (PBDB) schematics and board layout. The below diagrams have been updated to reflect the mandatory and optional board changes. This includes removing diode CR1 and reversing the polarity of capacitor C3. Also the values for R1 and C1 have been updated.

Optional Upgrades to the Pop Bumper Driver Board.
Starting with System80b, Gottlieb changed the value of two components on the pop bumper driver board. It is recommended changing these components; the pop bumpers will "pop" faster and have better action.
• Capacitor C1: change to 1 mfd 100 volt non-polarized (from .01 mfd).
• Resistor R1: change to 10k ohms 1/4 watt (from 1.5k ohms).

Problems that Capacitor C4 causes.
The capacitor C4 on the pop bumper driver board can go open, causing the entire pop bumper board not to function or to cause the pop bumper to energize randomly and multiple times. This cap is the filter for the two TTL chips on the board. Due to the large current drain and back spike when the bumper coil energizes, this cap often fails open. Since the cap doesn't short closed, lots of people never replace it. It is best to increase the size of this capacitor from 47 mfd to 100, 150 or even 200 mfd. This will help with the filtering. Lack of filtering can cause interference from other solenoids to simultaneously activate a pop bumper solenoid.

Replacing the PBDB's 2N6057/2N6059 with a TIP102.
Unfortunately the main driver transistor on the pop bumper driver board (the 2N6057/2N6059) is becoming hard to find, and very expensive. But there is good news. This transistor can be replaced with the easy to find and inexpensive TIP102. The only trick is mounting the transistor correctly to the pop bumper driver board. See the picture below for proper orientation of the TIP102. Before doing this, make sure *all* the mandatory and optional modifications have been performed to the PBDB. See the picture below for orientation of the TIP102 transistor in the PBDB. Notice the center transistor lead goes through the old 2N6057's bolt hole, and connects to the trace on the solder side of the board.

A Pop Bumper Driver Board with the 2N6057 replaced with a TIP102 transistor. This works amazingly well.

Adding LEDs to the Pop Bumper Driver Board (PBDB).
This is a S.Charland idea that is a nice feature for PBDBs. It is easy to add is a LED showing that +5 volts is on the PBDB. This LED should always be on, signifying the PBDB is ready for operation. The other added LED only comes on when the PBDB is fired. This LED shows that the input trigger has been closed, and that the PBDB is actually firing the driving transistor.

To add these two LEDs, you will need the following:

• (2) LEDs, any color or variety
• (2) 270 ohm resistors (or even 330 or 470 ohm)
• (1) 1N4004 diode

You will have to drill four 1/16" holes in the PBDB to accomodate the two LEDs. Also note the orientation of the FLAT side of the LED in the pictures below. For the +5 LED, the Flat LED lead goes to ground, and the round LED lead goes through the resistor to the +5 volt PBDB trace. For the Fire LED, the Flat LED lead goes to the connector pin that goes to the pop bumper coil's ground. And the round LED lead goes to the resistor and then to the banded side of a 1N4004 diode, and then to +5 volts.

The solder side of the PBDB where the two LEDs, two 330 ohm resistors, and a 1N4004 diode are added.

The newly mounted two LEDs on the PBDB showing +5 volts and the momentary "fire".

The Driver Board Transistors Explained.
First thing to remember about the System80 driver board is this: there are only SIX transistors (labeled solenoids 1,2,5,6,8,9) that are "dedicated" solenoid driver transistors. Three are the large 2N3055 transistors at Q58,Q62, Q64. The other three are the 2N6043 transistors at Q53,Q59,Q60. Since System80 games use Pop Bumper Driver Boards, there is no driver board transistor needed for the pop bumpers. Even still, six solenoid driver transistors is not a lot. Often, Gottlieb ran out of high powered driver transistors, so they used playfield mounted 2N5875 transistors to drive the additional coils. These playfield mounted transistors are "pre-driven" by driver board MPU-U45 (or MPS-A13) transistors (which are normally used to drive lamps).

As mentioned above, the other MPU-U45 and MPS-A13 driver board transistors trigger CPU controlled lamps. The small MPS-A13 can only drive a single lamp. The larger MPS-U45 can drive two lamps simutaneously. These can also be used to pre-drive a larger 2N5875 playfield mounted transistor for a coil. There is no "lamp matrix" either. So that means there has to be a separate transistor for each CPU controlled light (or pair of lights).

The MPU-U45 transistors can also control relays. Most System80 games have at minimum three relays: the coin door lockout relay coil (Q3), the tilt relay (Q2), and the game relay (Q1). The coin door lockout relay coil is almost always energized (when the coil is not energized, the coin door will not accept money). The game relay energizes when a game is started. This relay then turns on the solenoid power and sometimes general illumination lighting. The tilt relay energizes when the game is tilted.

There are also three MPU-U45 transistors dedicated for mechanical coin counters (labeled solenoids 3,4,7). This was an option Gottlieb offered, and required additional wiring (at connector A3-J6, added by the operator). I have personally *never* seen a system80 game with these optional mechanical coin counters. Because of this, the three MPU-U45 transistors at Q54,Q55,Q56 can be "stolen" and used when another MPU-U45 dies. The only exception to this rule is on some System80b games. Gottlieb finally figured out no one was buying the mechanical coin counter option, and decided to use these three transistors for "real" chores. It is easy to identify these driver boards; the diodes that are normally at CR2,CR3,CR4 are replaced with jumpers.

The above explains the system80 internal solenoid test. Ever wonder why only solenoids 1,2,5,6,8,9 were tested in test #17? Solenoids 3,4,7 are skipped because these are for the mechanical coin counters.

With the system80 game powered on, an alligator test wire can be used to test driver board transistors. Connect one lead of the test lead to ground. Then momentarily touch the other end of the test lead to the metal case or tab of any driver board transistor (except for the MPS-A13 transistors, which do not have a metal case or tab). This will energize the coil/lamp in question. On the metal cased 2N3055 transistors at Q58,Q62,Q64, this should fire a coil. Likewise for the metal tabed 2N6043 transistors at Q53,Q59,Q60. For the MPS-U45, grounding the metal tab usually just turns on a playfield lamp or two.

There are some expections to the MPU-U45 rule though. For example, transistors Q1,Q2,Q3 control the game relay, tilt relay and coin door lockout relay, respectively. So grounding these won't turn on any playfield lamps. Also MPS-U45 transistors Q57,Q61,Q63 are pre-drivers for the large 2N3055 driver board transistors, and when grounded, will do nothing. Also on many games (Black Hole/Haunted House for example), transistors Q13,Q14,Q15,Q16,Q17 are pre-drivers that feed to playfield mounted 2N5875 transistors. Hence grounding these MPS-U45 won't light any playfield lamps either.

Also some MPU-U45 transistors will be almost always "on" (providing ground to their repective devices). This includes Q49,Q50,Q51,Q52, which control certain playfield lamps set to mostly "on". These four transistors can be turned off by grounding chip Z12 pins 3,6,1,14 (respectively). Also transistor Q3 (coin door lock out relay) is nearly alway "on".

Test Fixture Driver Board Notes.
If using a test fixture, transistors Q57,Q61,Q63 (pre-drivers for the 2N3055s) and Q49,Q50,Q52,Q51 will be "on" (and grounding their metal tabs will do nothing). So don't flag these transistors as "shorted on" on the test fixture. Also transistors Q13,Q14,Q15,Q16,Q17 are often pre-drivers (and grounding their tabs often will do nothing), so don't flag these as bad on the test fixture either. These pre-driver Q13-Q17 transistors can be tested in the lamp test #16 though. These will energize their pre-driven coils in this test.

Internal Lamp/Solenoid Tests 16 and 17.
After the game is turned on and booted, pressing the red test button inside the coin door will show a "00" in the credit display. Press the game's start button to skip this number past the audits and to the first test, number 16 (the lamp test). After a second, the game relay will pulse twice, followed by the tilt relay pulsing twice, followed by the coin door lockout relay pulsing twice. Then the playfield lamps will turn on, starting with lamp L2 right up to the last lamp (L51). If lamp driver transistors are used to pre-drive under the playfield 2N5875 transistors (usually L12-L16 via Q13-Q17), these solenoids will also energize during the lamp test! The lamp test will continue this way for about 30 seconds (and then the test ends, and the game goes back to attract mode).

If the test button is pressed again (to test #17), the six dedicated coil transistors will be tested (solenoids 1,2,5,6,8,9 via transistor Q60,Q58,Q62,Q64,Q53,Q59 respecitively). This test will only happen once and will not repeat.

After doing the ground modifications on the Driver board, test all the MPS-U45 transistors (which control the playfield lamps and some solenoids), and the MPS-A13 transistors (which control the playfield lamps). It only takes a minute, it's real easy, and it prevents problems after the board is installed.

NOTE: 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.

Second note: inexpensive DMMs can give different results than seen below. Though not an issue on other game systems, for some reason the transistors used on the Gottlieb System80 driver board can give different results than shown below. I used a Fluke or Tenma meter to get the results below. If your DMM's diode test has a range lower than 2.000 volts (i.e. a cheap DMM), your results may be different and indicate faulty transistors, when they really are not faulty. It's best to test all of the same kind of transistor, and if one or two tests different than the others, that's a good indication those transistors are a problem.

MPS-U45 and MPS-A13 transistors (driver board Q1 to Q57, and Q63). 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 solder side of the board, put the RED lead of the DMM on the middle trace (the base) of the transistor.
• Put the BLACK lead of the DMM on either of the other 2 transistor traces, testing each of the two leads one at a time. A reading of about 1.3 on the emitter (ground) lead, and .7 on the collector should be seen. Anything within .1 of these values is good. On the MPS-U45's, the emitter is the transistor lead closest to the bottom edge connectors.
• 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 Failure Examples.
I had a lamp that was constantly locked-on ("shoot again"). When the Driver board transistor was tested, it showed .7 on the collector, and .5 on the emitter (it should have been 1.3). Replacing the MPS-U45 transistor fixed this lamp problem.

On another Driver board transistor, I had a reading of 1.2 on one lead, and no reading (zero) on another. This transistor controlled the solenoid for the ball release to the shooter lane, and the solenoid was locked on when a game was started. Replacing this MPS-U45 transistor fixed that problem.

2N6043 transistors (driver board locations Q53, Q59, Q60). This transistor tests the same in circuit and out of circuit.

• Set the DMM to the "diode" setting.
• Put the black lead on the center lead of the 2N6043 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.

2N3055 transistors (driver board Q58, Q62, Q64, large transistors with the huge metal case). 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 of the 2N3055, and the red lead on each leg one at a time. A reading of .4 to .6 for one leg, and no reading for the other leg should be seen.
• Now put the red lead on the "base" lead (see picture below in step 4) of the transistor. Put the black lead on the other 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).
• Also check the three BIG 1 watt 9.1 ohm resistors connecting to the 2n3005 transistors (these should test 9 or 10 ohms in circuit).

A removed driver board 2N3055 transistor showing the emitter, base and collector.

PMD10K40/2N6057/2N6059 Pop Bumper Board/Power Supply transistor:
• Test the large metal Q1 power transistor installed in the pop bumper driver board and on the power supply board. Set the DMM to the "diode" setting.
• Put the black lead on the metal case of the transistor (or on the bottom attachment screw of the pop bumper board transistor), and the red lead on each leg. A reading of .4 to .6 for each transistor leg should be seen. Anything else and this transistor is bad.

2N5875/2N5879/2N5883 Playfield Mounted Transistors:

• Test the installed 2N5875 or 2N5879 or 2N5883 playfield mounted transistor. Set the DMM to "diode" setting.
• If an under-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-PF 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-PF 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.

Problems with locked on solenoids? It could be a ground problem! (See the manadtory 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)

System 80 uses several different transistors:
• MPS-U45 or NTE272: main driver transistor used on the Driver board for solenoids and lamps. CENT-U45 is an excellent replacement. This is an NPN darlington power amplifier transistor, 50v, 2amp.
• MPS-A13 or NTE46: driver transistor used on the Driver board to drive lamps. Silicon NPN transistor, 100v, 500mA.
• 2N5875 or 2N5879: Under playfield mounted driver transistor. Used only on Volcano, Black Hole, Haunted House and others because they ran out of MPS-U45's on the Driver board for driving solenoids. These are PNP medium speed switching transistors, 100v, 15amp. Can use NTE219 or NTE180 (which is 100v, 30amps)
• 2N3055: Three used on the Driver board for heavy duty solenoids. These are NPN medium speed switching transistors, 100v, 15amp. Same as NTE130 or NTE181 (100v, 30amp.)
• 2N6057: Same as a 2N6059. Used on Pop Bumper Driver board and Power Supply board. Also known as PMD10K40 or NTE247. 2N6057's are hard to get, replace with 2N6059. These are NPN darlington transistors 100v, 12amp. Can also use NTE249 which is 100v, 16amp.
• 2N6043: Used on the Driver board for medium duty solenoids. This is a NPN, 100v, 8amp darlington transistors. NTE261 or TIP102 is a good replacement.
• TIP31C or SW4F013 or NTE291: Used on Power Supply board. General purpose NPN transistor, 100v, 4amp.
• 2N5550 or NTE194: Used on Power Supply board for high voltage section. Can be replaced with a 2N5551 (higher maximum voltage rating), or even a medium signal transistor like 2N2222 or 2N1711. Silicon NPN amplifer.
• 2N4400: Same as a 2N4401 or 2N2222. Used on CPU board Q2/Q3 in the reset/startup section.
• 2N4403: Used on Power Supply board.
• MPS-A70: Same as 2N4403 or 2N2907. Used on CPU board Q1/Q4 in the reset/startup section.

There are some substitutes for the above transistors. Most notably are the NTE and ECG replacements. These companies use the same part numbers (i.e. NTE262 = ECG262). NTE has a great free utility for cross referencing their part numbers. Get this software at http://www.nteinc.com. NTE and ECG parts are usually available locally. The cheapest place to get all these transistors is Mouser Electronics (800-346-6873) http://www.mouser.com.

Suggested Substitutes

• MPS-A13 = NTE46
• MPS-U45 = NTE272 = CEN-U45
• 2N5875/2N5879 = NTE180
• 2N3055 = NTE130
• 2N6043 = NTE261 = TIP122 = TIP102
• 2N6057/2N6059/PMD10K40 = NTE247
• 2N5550/2N5551 = NTE194
• 2N4400/2N4401 = NTE123AP
• 2N4403/MPS-A70 = NTE159
• TIP31C = NTE291
• UDN6118 = NTE2021 (a chip used for the displays)

Note for the 2N5875 always replace it with 2N5879 or better. Here are the ratings for all the substitutes for the 2N5875:

• 2N5875 = 10 amps 60 volts 150 watts (not recommended)
• NTE219 = 15 amps 70 volts 115 watts (replacement for 2N5875)
• MJ2955 = 15 amps 60 volts ? watts
• 2N5879 = 15 amp 60 volts 160 watts
• 2N5880 = 15 amp 80 volts 160 watts
• 2N5883 = 25 amp 60 volts 200 watts
• 2N5884 = 25 amp 80 volts 200 watts
• NTE180 = 30 amps 100 volts 200 watts (replacement for 2N5879 to 2N5884)
Note the amp rating is more important than the voltage.

Using TIP102 instead of MPS-U45 Transistors.
I really hate MPS-U45 transistors! They are only rated 10 watts at 40 volts of power dissipation, and they have really whimpy leads, which can break easily. MPS-U45s are also getting hard to find, and expensive. Finding a substitute for this crappy little darlington transistor was top on my list of priorities.

My first hope was to use the TIP102 (as used by Williams). These have a power dissipation of 80 watts at 120 volts, and are in a much more robust case. Finally they are plentiful and inexpensive.

The trick to installing a TIP102 instead of a MPS-U45 is the legs are packaged differently. The MPU-U45 legs are E B C. The TIP102 is B C E. So to install a TIP102, it must be installed "backwards", and have the C and B legs "twisted". This makes the TIP102 package align to the same pin configuration as the MPS-U45. See the picture below for details.

Central Labs also sells a very good MPS-U45 replacement, known as the CEN-U45. These come in a TIP102 style case, and are a direct replacement for the MPS-U45. Highly recommended!

Installing TIP102 transistors in place of MPS-U45 transistors. Note the "twisted" C and B legs of the TIP102. NOT RECOMMENDED.

Is Using a TIP102 Really the Right Thing to Do?
Now the above can work (that is, it will drive a lamp or a coil), but will it work correctly? Good question! The answer may be "no". But first we need to understand how transistors work on a System80 driver board.

When the output from the driver board's 74LS175 is low, the associated transistor is off, and essentially there is no current flow. When the 74LS175's output is high, the transistors is on, and there is considerable current flow. The output current that is significant here is the "source current" or IOH.

A 74LS175 outputs 400 microamps maximum when the output is high (the 74175 outputs 800 microamps). Either works nicely with the MPS-U45 or MPS-A13 transistors, since both have incredibly high current gains. But the TIP102 has 1/10 of the current gains of the MPS transistors. Plus it requires a higher Base-Emitter voltage to put the TIP102 into "saturation" (a transistor is fully "on" when it is saturated, and transistors can be partially turned on otherwise; a partially turned on transistor can lead to a weak solenoid/lamp).

Going by spec, the TIP102 won't work here. It needs a higher input current and voltage. But often IC manufacturers are pretty tight on their specs, and the 74LS175 may be able to output more current than it is rated. The 74LS175 could drive the TIP102, but certainly not into saturation. And the additional current draw from the 74LS175 could shorten the life of the chip. In a pinch it may work, but it is certainly not recommended for a long term fix.

Another approach would be to change the current limiting resistor (currently 1000 ohms) that connects from the 74LS175's output to the transistor's base. But this probably wouldn't have much affect in driving a TIP102. The 74LS175 can only output so much current before the output voltage starts to drop. By spec the 74LS175's output current is less than 1 microamps. Reducing the resistor increases the voltage to the transistor, but not the current. This causes a smaller voltage drop across the resistor and presents a higher voltage to the base of the transistor. Yet the 74LS175 is still limited to 400 to 800 microamps on its output current.

The MPS transistors have a minimum current gain of 10,000 (quite high!) Under ideal conditions, the MPS-U45 can sink a 4 amp load (10,000x400 microamps) in theory. In addition to the high gain, the U45 also has a very low collector to emitter saturation voltage. This means that there would be little voltage drop across the transistor, causing brighter lamps.

The TIP102 has a minimum current of 1000 (still quite high). But the TIP102 can sink only a .4 amp load (1000 x 400mA). Barely enough to light two #44 bulbs. Plus the TIP102 has a higher saturation voltage, meaning dimmer lights.

TIP102s and the Under-Playfield Transistors?
If TIP102s could be used, would there still be a need for under the playfield 2N5875 transistors? The reason under the playfield 2N5875 transistors were used is because Gottlieb ran out of solenoid driver transistors on the driver board. So instead they used the MPS-U45 lamp driver transistor to "pre-drive" the under the playfield 2N5875 transistor. But with a TIP102 installed on the driver board, could the under the playfield 2N5875 be eliminated? Mechanically this is easy to do; just remove the single wire from the Emitter and Base leads of the 2N5875, and tie them together (make sure to leave the +24 volt wire lead on the 2N5875's Base, which is connected to a 4.7k resistor). But again, this may not be the "right" thing to do.

Every Gottlieb System80 has a "slam" switch inside the coin door. On games prior to Big House (CPU board MA-1133 System 80B), the Coin Door Slam Switch is normally closed. This closed slam switch *must* work or the game will not boot (system80b games Big House and later have a normally open coin door slam switch, so the information here does not apply to those games - on these games the CPU was changed to a MA-1133, which is different from the earlier system80b CPU board because it has a jumper wire on the solder side from TC1, a cut trace on the component side, and a larger EPROM in socket 2). That is on sys80b games Bad Girls, Big House, Hot Shots, and Bone Busters the slam switch is normally OPEN, as Gottlieb saw the light and conformed to the way other manufacturers used the slam switch. Slam switches were installed to calm over-agressive players, ending the current game and rebooting if someone hits the coin door too hard.

The problem with the slam switch on pre-Big House games is it's a "normally closed" switch. This means if the slam switch is open for any reason (or the CPU board connector A1J5 pin 10 going to the slam switch has failed), the game will not start until the switch is closed. This contrasts most other manufacturer's games (and Gottlieb games Big House and later) which have a normally open slam switch. If a System80 coin door slam switch is dirty, bent, cut or damaged, or if the wire going from the CPU board to the slam switch is cut, or the connector at the CPU board is damaged, the game will never power on properly. Finding this problem can be very frustrating.

The symptom of an open slam switch is the game turns on, and immediately all four display strobe "000000". This is unlike the normal system80 boot procedure where the displays are blank for about 4 seconds, and then come on and alternate between zero and the high score.

Crossing two traces right on the CPU board to permanently close and disable the coin door slam switch.

A solution to this problem is to modify the pre-Big House System80 CPU board so the slam switch is permanently closed, no matter what the condition of the slam switch itself. By modifying the CPU board, the slam switch could be removed and it will have no ill effect on game start up.

To make this modification, cross the two traces on the component side of the CPU board's, just right of Z26. These traces are right next to each other. Just scrap the solder mask, and jump the traces with some solder and wire. This makes the slam switch permanently closed, regardless of the condition of the coin door slam switch.

Cutting the Slam Switch wire on the CPU board Connector.
After making the CPU board jump to permanently close the slam switch, cut the wire from the CPU connector that goes to the slam switch. This is important because when cut, the slam switch on the coin door can not be accidentally shorted. The coin door has +25 volts, which is used for the coin lockout coils. If this +25 volts is accidently crossed to the slam switch, this will toast the CPU board. Having the slam switch wire cut at the CPU board connector will prevent this potential problem. Be sure to label this wire as a "cut slam switch" in case an unmodified CPU board is installed.

On the CPU board, connector A1J5 pin 10 is the slam switch wire. This should be a white wire with purple and black stripes (to confirm, look at the slam switch on the coin door and one of the two wires should be the same color as the wire at A1J5-10). Cut it right at the connector. Make sure the above CPU board modification is made too, or the game will be permanently in "slam" mode!