Game plays but resets randomly; wall voltage is above about 116 V.

Pre-WPC-95 resets: replace BR2, C5, C4 and the J101 pins together

Cause: On WPC-S and earlier the 5 V bridge BR2, its 15,000 mfd filter C5, the 100 mfd keep-alive C4 and worn J101 pins are the usual culprits, along with cracked solder pads around BR2 and C5. On WPC-95 the equivalent parts are diodes D7-D10, C9/C1 and connector J129.

Checks

• Confirm wall voltage first.
• Look for cracked solder around BR2 and C5.

Fix

• Replace BR2, C5 and C4 (with 470 or 1000 mfd) and repin J101 at the same time; the guide says this cures about 95% of resets.
• On the solder side run jumper wires from the BR2 "+" lead to the C5 "+" lead and from the BR2 "-" lead to the C5 "-" lead.
• Check continuity from the lower-left BR2 AC pad to D3 (right end), and between D38 (right end) and the upper-right BR2 AC lead; these feed the zero-cross diodes.

Systems

• WPC Alpha-Numeric
• WPC Dot Matrix
• WPC Fliptronics
• WPC DCS
• WPC-Security (WPC-S)

Related tips

• Bridge rectifiers to use on WPC-S and earlier driver boards
• Driver board filter capacitors wear out
• Replacement bridge rectifier and diode ratings
• Choosing a replacement driver board filter capacitor
• Getaway: beacon runs nonstop in test and driver board C11 overheats
• Raising the WPC/WPC-S +5 V to about 5.15 V (last-resort reset fix)
• What a WPC game reset is
• Resets during the Powerball battle: reseat J101 and J115 on the power driver

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