The game reset part way through the Powerball battle, when several coils and flashers fire together; normal play was otherwise fine.

Resets during the Powerball battle: reseat J101 and J115 on the power driver

Cause: Poor contact at the power driver board connectors J101 and J115 let the logic supply dip under the heavier load of that mode.

Checks

• With the game off, look at J101 and J115 on the power driver board for discoloured pins or loose, browned housings.
• Check the logic 5V at the CPU board while the game is running; it should stay close to 5V.

Fix

• Reseat J101 and J115 (and ideally the other power driver connectors). If any pins look burnt, replace the header and the connector housing and pins rather than just reseating.

The power driver board carries transformer AC and high-voltage coil supplies; unplug the game before touching connectors.

Systems

• WPC Fliptronics

Games

• Twilight Zone

Related tips

• No coils, lamps, GI or flashers but display and sound work: check blanking
• Resets: +5 V at the driver board test point is low
• Pre-WPC-95 resets: replace BR2, C5, C4 and the J101 pins together
• Reboots at start-up and when flipping: flaky power connector to the CPU
• Gumball diverter, popper and two bumpers dead in test: faulty CPU ribbon
• Resets or dead banks of coils or lamps from cracked bridge or cap solder
• What a WPC game reset is
• Watching the supplies while the game resets

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