Resets during play; +5 V at TP2 (TP101 on WPC-95) reads under 4.92 V in attract mode.

Resets: +5 V at the driver board test point is low

Cause: Most often the 5 V bridge BR2 (diodes D7-D10 on WPC-95) and its filter capacitor C5 (C9 on WPC-95); sometimes the regulator (Q1, LM323K; LM317 on WPC-95); very often the power input connector J101 (J129 on WPC-95) or the 5 V output to the CPU board, J114 (J101 on WPC-95).

Checks

• Game on in attract mode. TP2 should read 4.92-5.1 V DC.
• Do not unplug or reseat any connector yet; doing so hides which one is bad.
• Measure +5 V on the CPU board at pin 32 of the game EPROM. If it is even slightly lower than at TP2, the connectors between the boards are bad.
• Reseat J101 only and recheck TP2; a rise means J101 is bad. Then reseat J114 (J101 on WPC-95) and recheck at the EPROM; then CPU connector J210 and any "Z" connector.

Fix

• Any connector whose reseat changes the voltage must be repinned with new Trifurcon pins, with new header pins or a wire-brushed header; original IDC connectors need a new housing too.

Systems

• WPC Alpha-Numeric
• WPC Dot Matrix
• WPC Fliptronics
• WPC DCS
• WPC-Security (WPC-S)
• WPC-95

Related tips

• Resets remain after rectifiers, caps and connectors are done
• WPC power driver bridge rectifiers and +5 V regulator
• WPC-89 resets on low +5 V: replace the small 100 uF 5 V filter caps
• Replacing the 78H05 +5 V regulator
• Aftermarket "C" supply: 68 V zeners burn at power-on
• What a WPC game reset is
• Resets during the Powerball battle: reseat J101 and J115 on the power driver
• Game keeps resetting during play: poor J101/J102 power connections

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