Hey folks,
This is my first post to the forum but have been a pinside member for a little while. The forum restoration content from all the experienced folks has been beyond invaluable and has gotten me to this point. I'm very appreciative!

I am a restoration newbie but fell in love with the process after doing minor fixes and upgrades to my first pins over the last couple years. Last winter I dove into the deep end with a Williams Flash system 4 I picked up that was really ready for the dumpster. It was probably ridiculous to try and save it, but in retrospect worth it due to what I have already learned. Anyhow, I was what I thought was in the final stretch with almost everything working after major work on all the boards, mechanics and cosmetics following the forum guidance (bulletproofing guides, vid's restorations, and expert fixes) until I hit a wall.

More background:
- Implemented power supply bulletproofing, re-capped, etc. and all checks out good.
- MPU checks out good, as well, the game worked all except for switches in matrix column #3 (see below). Replaced a suspect timer crystal and capacitor and minor bulletproofing. All checked out good.
- Unrelated, but bullet proofed and fixed everything with the soundboard.
- Replaced many coils, diodes oriented correctly (I believe) and all checked out when doing the coil test. (I did have one diode incorrect and had to replace the associated transistors on the driver board and all checked out fine).
- Redid many connectors.

The initial problems:
Pin went into attract mode fine and would start a game. Game would play and score fine with exceptions.
1. The two upper left star rollover lights are always stuck on both during attract and play mode.
2. All switches relating to column 3 in the switch matrix were not working, scoring, etc.

- Believe I verified all caps (replaced one on a pop bumper) and diodes are good under the playfield.
- Believe I verified all wiring is good through connectors (replaced due to heat damage) through to driver board.
- Believe part of the problem is tied to switch column (drive) section on the driver board. Voltage at #7 in the switch column drive connector was low. Found three bad resistors and one shorted capacitor (C51) in that section.
- Also found what appears to be a shorted Transistor at Q47 in the lamp row drive section.
- Did my best to test entire board with a DMM and did not discover any other problems. There may definitely be some, but I am a newbie!
- The board already had the resistor upgrades in place.

So, I replaced the problem resistors, transistors, and capacitors according to the parts list with the schematic. One problem is that it was very hard to determine the part specification for the replacement capacitor in position C51. Totally unreadable to me in the documentation online and printed. I thought I had it correct and now think I got it wrong.

Final problem:
Turned on the game and it went into attract mode briefly - then the driver board started smoking and I had to shut it off. I fear I put in the wrong capacitor or maybe something else.
- Verified with the DMM the new capacitor is shorted, new resistors are fried, and the transistor appears shorted again (Q47).
- Also highly suspect that IC17 is fried. Couldn't exactly tell where the smoke came from but a resistor (R206 I believe and one I had replaced) was super hot as well as IC17 was pretty darn hot.

My newbie attempt to fix things clearly did more damage so any guidance / insight is super appreciated.
- I have replacements for the IC (and will install a good socket) as well as the resistors and transistor.

Questions:
- Does anyone know the capacitor specs or have a link for the replacement I should use for C51?
- Is the Q47 transistor related to the two locked on rollover lights or something else? If something else, then where should I look for that problem and what does Q47 short relate to?

Clearly the work I did caused the problem so I am assuming it is related to the capacitor but I may be wrong. And was I even fixing the right stuff for the behavior I was seeing. Last note, some previous owner had replaced the same resistors that were reading bad in the switch column drive area.

I'd like to give fixing the board one more shot, since so much time and effort has been invested to get to this point (and $$) vs. buying a replacement board but I am at my wits end and now over my head. I just want the final feeling of bringing this back to life and actually start enjoying it as well as devoting more time to enjoying the pins we have.

Any guidance from experts is greatly appreciated. I've attached a clip of the driver board schematic.
Thanks for reading.
Desertguy

#Williams Flash