It almost looks like it is resetting. I would start by checking the
transistor that fires that kickback. It's possible that if you have a
problem with that coil then it could be dropping your 5 volt line and
I am by no means a professional pinball repair man but this sounds
similar to some WPC issues I have read about when I had a reset issue so
that's what I would test first.
> It just does this pulse. I assume a power board issue, but could use some opinions on where to start.
> Thanks, Mike.
Verify wall voltage. Then disconnect everything from the power supply board to isolate it and check all your voltages first. If they are all within tolerance then connect the MPU board and see that it boots correctly. If not then you'll know the issue is one one of those boards or in a connector.
To me it looks like the power supply is dropping out.
Here are a couple of sections from a repair manual that might help.
+5 volt Filter Capacitor(s). The +5 volt logic filter capacitor on the power supply board is very
important. This keeps the +5 volts smooth and steady. If this capacitor
fails, the +5 volts can become rough, and cause the CPU to reset during
game play. This can often be seen during game play, when both flipper
buttons are pressed, or during multiball when a lot of coils are firing
Power supplies #520-5047-00, #520-5047-01, #520-5047-02 (Laser War to
Guns N Roses) used a single 18,000 mfd 25 volt capacitor at C4 to filter
the +5 volts logic. When DataEast/Sega switched to the super-sized
192x64 dot matrix display, the power supply changed to #520-5047-03.
This newer version switched from a single 18,000 mfd filter capacitor,
to four 4700 mfd 25 volt caps at C11 to C14 (for a total of 18,800 mfd).
This was done for reliability reasons. If one of the capacitors failed,
the other three could probably still filter the +5 volts enough to keep
the game running.
For additional reliability on games Laser War to Guns N Roses, it is a
good idea to solder an 18 gauge wire from the "+" lead of bridge DB1 to
the "+" lead of capacitor C4. Solder another 18 gauge wire from the "-"
lead of the bridge DB1 (the lead diagonal to the bridge's "+" lead) to
the "-" lead of capacitor C1. These added wires will help prevent future
problems with cracked solder joints on the power supply board
Power Supply Connectors CN1 and CN2. On the power supply there are two "square" connectors (opposed to the
inline connectors). Connector CN1 provides incoming power to the power
supply board. Connector CN2 is a centralized ground plug. If either of
these connectors have cracked or cold solder joints on the power supply
board, random game resets can occur. Check these connectors for cracked
or burnt pins on both the power supply board, and the connector plug.
Power Supply Missing +5 volts. If +5 volts is missing on the power supply, the obvious culprits are IC1
(a MC1723 chip) and transistor TR5 (2N6057). These essentially regulate
the +5 volts. But before replacing these, check the surrounding
capacitors. This includes C2 (100mfd 25v), C3 (47mfd 25v), C5 (470p
50v), C6 (.1mfd 50v), and C7 (330mfd 25v).
Actually to clarify, I need a pic of the wire colors on CN8. Someone cut off the connector and soldered lengths of wire to the back of the board. Then wire nutted those lengths to the factory wire. Wire nuts and some of the factory wire got melted. I need a closeup pic so I can restore it back to factory with a new connector and pins.
Ok guys, pulled the power board and replaced C2. I have 4.94v at the test point on the power board. I have 4.93 at the connector for the MPU. But I have 4.87v on the MPU test point. I hope this is OK. It seems to boot every time now. I will wait until it gets cold again and thats when it would never boot. Fingers crossed.
Can't beleive one lousy cap at C2 would cause an entire game not to boot.
> Actually to clarify, I need a pic of the wire colors on CN8. Someone cut off the connector and soldered lengths of wire to the back of the board. Then wire nutted those lengths to the factory wire. Wire nuts and some of the factory wire got melted. I need a closeup pic so I can restore it back to factory with a new connector and pins.