Random resets, or a dead game that boots after a connector is wiggled or reseated.

Resets from worn power connectors between transformer, driver and CPU boards

Cause: Resistance in the power connectors: J101 (J129 on WPC-95) brings transformer AC to the driver board, J114 (J101 on WPC-95) takes 5 V to the CPU board, J210 is the CPU board input, plus any inline "Z" connector, J102 (J128 on WPC-95, 16 V AC), J112 (J127 on WPC-95, 9.8 V AC) and the transformer plugs. Cracked header solder joints are common, especially on Twilight Zone.

Checks

• Reseat each connector in turn and see whether the resets change.
• Reseat the transformer plugs in the bottom of the cabinet.

Fix

• A change after reseating is only a temporary fix. Replace the housing pins with .156" Trifurcon pins, and the board header pins as well.

Systems

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

Related tips

• GI string dead with a scorched connector
• GI connectors on the driver board
• GI out because the GI connector burned
• CPU board switch connectors
• Repair a burnt GI connector on the driver board
• Check the AC power input connectors too
• Lamp matrix connectors on the driver board
• Backbox GI out while flashers work: burnt connectors at J120 and J121

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