The speakers are silent and the board seems alive.

No audio output at all from the sound board

Cause: Usually the LM1875 power amplifier; also the sound ROM, sound RAM or the MC3340 attenuator. A dead board usually has lost +12 V or -12 V.

Checks

• Measure the LM1875: -26 V on pin 3 and +26 V on pin 5.
• Check the ROM and RAM outputs for pulses.
• Check fuses F501 and F502.

Fix

• Replace the amplifier, fuse or failed chip.

Systems

• WPC Alpha-Numeric
• WPC Dot Matrix
• WPC Fliptronics

Related tips

• WPC sound board versions
• WPC-89 sound board layout
• The WPC sound board runs on its own
• WPC sound board silent, no power-up bong: try the RAM first
• Loud hum at power-up and the cabinet speaker burns: shorted audio amplifier chip
• Sound board RAM error at U9, wrong call-outs or no sound: replace the U9 RAM
• Random stray sounds in attract mode after changing the CPU board
• Sound and DMD controller fuses (WPC-89 and WPC-S)

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