Random resets, or a whole group of coils or lamps quits, while the bridge and cap test good.

Resets or dead banks of coils or lamps from cracked bridge or cap solder

Cause: The heavy bridges and filter capacitors heat and vibrate, so their joints and plated-through holes crack. The board is double-sided and the component-side traces cannot be soldered, so reflowing the bottom does not always restore them.

Checks

• Inspect the solder joints of the bridges or diodes and their filter capacitors.

Fix

• Reflow the joints with fresh solder.
• Add backup jumper wires on the solder side from the rectifier outputs to the capacitor leads (see the jumper entries).

Systems

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

Related tips

• Resets and GI that will not dim after BR2 was replaced
• Resets remain after rectifiers, caps and connectors are done
• Resets when the knocker fires, hum and DMD glitches: cracked power board joints
• Resets continue although the bridge and diodes test good
• What a WPC game reset is
• Resets when a drop target or coil fires: burnt power and GI connectors
• Watching the supplies while the game resets
• 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)