After an accidental short on the -125 V supply (blowing F602 and burning R30), the game won't start with the A/V board connected; +5 V at the A/V board reads about 3.5 V, but the game boots without sound when the board is unplugged.

WPC-95 won't boot with the A/V board plugged in after a -125 V short

Cause: A failed sound EPROM loading the 5 V supply is the first thing to rule out.

Checks

• With the game off, remove all the sound EPROMs and power up. A double bong for missing ROMs with the game otherwise starting points to a bad EPROM.

Fix

• Replace the bad sound EPROM, plus F602 and R30.

The A/V board carries the display high voltage; work on it unplugged.

Systems

• WPC-95

Related tips

• Early WPC-95 games: static or thin, tinny sound
• DCS or WPC-95 sound faults: amps and op-amps
• WPC-95 audio/visual board LED and beep codes
• Sound cuts out or a rising shriek after a few minutes
• NBA Fastbreak: adding the serial port for linked play
• WPC sound board versions
• The WPC sound board runs on its own
• Line out on DCS and WPC-95 sound boards

Source: Repairing Williams/Bally WPC Pinball Games from 1990 to 1999, Part Three, Clay Harrell (pinrepair.com)