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.

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 or 2N6059) 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 2N3