OP

Quoted from DruTheFu:

I'm hoping to get out to my garagecade tonight with my multimeter to check out the transistors on the ‘8-Driver PCB” board (A-16100)....again. I 'thought' I resolved the Upper Right Flipper flasher previously, as it was working, but an issue seems to have arisen again. I'm beginning to suspect there may be an underlying issue at play causing the two flashers to lock on.
I'll also use the multimeter to to check out the Left Ramp switch that doesn't seem to 'close'.
Any tips or advice for where to begin with the lamp issue mentioned above, for multiple lamps turning on during the single lamps tests?

OP

Quoted from DruTheFu:

Soooooo........
I removed the 8-Driver PCB board (A-16100) to test the transistors to check if a blown transistors were causing the Upper Right Flipper flasher (37) and Upper Right Ramp flasher (41) to 'lock on'. All of the transistors tested back good, having readings within the 0.4 - 0.7 range. Having the board already out, I figured to test all the transistors, resistors, and diodes. All readings for each type were fairly close to the others, with no reading being an anomaly far off from others that tested for the same type.
Back to the drawing board, and to figure out what to troubleshoot next for the two malfunctioning flashers.
Moving on to the troubleshooting of the multiple lamps lighting up during the Single Lamp test, I followed the suggestion of dsuperbee above in Post #13 and tested transistors Q86, Q91, and Q96, along with the diodes in the same rows/columns. To do this, I had to remove the entire WPC Power Driver Assembly board. Seeing what was visible in the backbox while the board was mounted, I could tell that the board had previously been worked on, as I could see that Q54, U3, R1, R2, R93, among some others had been replaced.

Once the board was unmounted and out of the backbox, I flipped it over, and saw this:

Looking at the back of the board, I can see that it's definitely had some work done to it. Using wires to jump to other components on the board, some soders that look a little suspect, etc.
On to testing the transistors Q86, Q91, and Q96. The readings for Q86 came back as good, but the readings for Q91 - Q98 were ALL bad. Looks like all those transistors are no good. With the condition of this board, and 8 transistors testing as bad, I'm thinking of starting anew and buying an entire new board, which makes me cringe a little knowing that it is the expensive board to replace.
I'm starting to think that I'm going down the road of purchasing new Rottendog boards to replace the WPC Power Driver Assembly board, the 8-Driver PCB Assembly board, and the WPC CPU board to have a fresh start and work with new, known good boards.
The wife's gonna love me now.....

OP

Quoted from DruTheFu:

OK, finally had some time to test out based on the above suggestions regarding my lamp test and the multiple lamps lighting up when performing the Single Lamp Test, along with the "Repairing Williams/Bally WPC Pinball Games from 1990 to 1999" guide. Before I began, I replace the Power Driver board with a Rottendog I just purchased.
I've tested the lamp columns on J137, and the test lamp flashes for every column.
I've tested the lamp rows on J133, and the test lamp flashes for every row.
Not a single column or row failed to light when tested going between each and every pin. This is leading me to believe the issue may be under the PF with wiring or diodes. I'm going to start checking under there, but wondering if anyone has any suggestions for what to specifically check? I'm going to look at solder connections, maybe diodes?
I'm open for any ideas that come my way. Thanks!!!
UPDATE #1: I unplugged the Slot Machine lamp (#85), and all single lamp tests are successful with no other lamps lighting up. While the Slot Machine lamp was unplugged, I removed the plastic and the entire lamp socket itself. I decided to unsolder the corresponding wires from the socket, cleaned it up, and resoldered the wires and a new 1N4001 diode to the socket. After reassembling the socket and plastic to the PF, I fired the machine up, and the same behavior persists.