The game resets every time the second ball is locked for the second (three-ball) multiball, but only when the right visor hole is locked first and the left one second. The first multiball, double flipping and the 5 V at the ROM all look fine.

Game reboots the instant the second visor lock is made in later multiballs

Cause: A fault on the power driver board: when the extra coils fire for the bigger multiball the logic supply dips and the CPU resets.

Checks

• Check the switch edges test while locking a ball to rule out a second switch closing.
• Fire every coil in coil test and watch for one that resets the game.
• Measure 5 V at the CPU while the fault happens if you have a scope or a fast meter.

Fix

• Swap in a known-good power driver board; here that stopped the resets. Then repair the original board (connectors, bridge rectifiers, filter capacitors) before reusing it.

Systems

• WPC-95

Games

• Jack•Bot

Related tips

• What a WPC game reset is
• Watching the supplies while the game resets
• Resets remain after rectifiers, caps and connectors are done
• Resets continue although the bridge and diodes test good
• Resets: +5 V at the driver board test point is low
• Resets or dead banks of coils or lamps from cracked bridge or cap solder
• Finding a board or device that drags the +5 V down
• Replace the +5 V filter capacitor on any game ten years or older

Source: Pinball Repair help group!! (Facebook group)