TECH HELP: WPC-95 Junkyard Power Driver Board

I've been working on my Williams Junkyard (WPC-95), but I've come
across some problems, and I need some advice. I've read a lot of
material, googled the group, but have found nothing that specifically
addresses my problem.

The project first started when I replaced some transistors on the power
driver board. I had a bunch of playfield lights that weren't working
properly (some would stay on, others wouldn't blink in sequence
properly). I replaced a TIP102 and a TIP106 transistor. This fixed the
light problems, but shortly after I replaced these transistors, the
game would reset itself continiously for about 15 minutes after I
turned it on (basically until it warmed up, but occassionally beyond
this point too). This was while the game was in attract mode, it has
nothing to do with flippers, or other high-draw devices.

I checked the line voltage at the plug, and it was fine. The pinball
machine is on its own separate circuit. I also checked the voltages at
the test points on the power driver board. They all checked out
properly, and did not "drop" when the machine was in the process of
resetting.

I went to marvin3m.com and read their repair logs. They suggested I
reflow the cold solder joints around all of the header pins. They also
suggested I replace the 10,000mF 25V filter capacitor at C9 with a
15,000mF 25V "Panasonic snap-cap" capacitor from DigiKey. I did this,
but it didn't put an end to the reset problems.

Next marvin3m.com suggested I replace the rectifier diodes at D7, D8,
D9 and D10. They suggested using NTE5814 400V, 6A diodes (from
mouser.com), which replaced 200V, 6A diodes that were on the board.
The diodes were installed with the band placed in the same direction as
the original diodes.

When I did this, the machine wouldn't even start up into its initial
test routine. I took the board back out, and applied some solder to
the top of the circuit board, around the diode leads, thinking since it
is a double sided board, and it uses plated-through holes, maybe the
solder wasn't making good contact.

When I put the board back in this time, it blew the 630mA, 250V fuse at
F101. (Regulated 12V).

I'm a little uncertain as to what to do next. Any ideas would be
appreciated. Thanks!

Blaine.

.

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