After five or more minutes of play the sound drops out, or a very loud tone builds up; it returns soon after a restart.

Sound cuts out or a rising shriek after a few minutes

Cause: Poor heat sink contact on the TDA2030A amps lets them overheat.

Checks

• Feel whether the amps run very hot.

Fix

• Unbolt the heat sinks, renew the heat sink compound and refit them with lock washers or kep nuts so they stay tight.
• Use the TDA2030A, not the lower-rated TDA2030, which distorts at high volume.

Systems

• WPC DCS
• WPC-Security (WPC-S)
• WPC-95

Related tips

• Loud foghorn noise at power-on after recapping the DCS sound board: broken through-hole
• Deafening hum at power-on: cracked ground trace at the DCS sound board filter caps
• Sound board beep codes, WPC-DCS and WPC-S
• DCS or WPC-95 sound faults: amps and op-amps
• WPC-95 won't boot with the A/V board plugged in after a -125 V short
• WPC-95 audio/visual board LED and beep codes
• NBA Fastbreak: adding the serial port for linked play
• No sound or sound cutting out

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