The CPU resets when several coils fire at once, such as both flipper buttons held or during multiball.

Resets when both flippers are held or in multiball

Cause: The power supply's +5 V logic filter capacitor has dried out, so the +5 V sags or gets ripple under load.

Checks

• Check the +5 V at the CPU board test points while flipping.

Fix

• Replace the filter capacitor(s): C4 (18,000 uF 25 V) on 520-5047-00/-01/-02 supplies, or C11-C14 (4,700 uF 25 V each) on 520-5047-03.

Systems

• Data East CPU Version 1/2
• Data East CPU Version 3
• Data East/Sega CPU Version 3b

Related tips

• Random resets from the power supply DB1 bridge
• After a bulb change, coils dead and a flasher fires the knocker: blown supply fuse
• Resets from power supply connectors CN1 and CN2
• Low-power solenoid voltage drops to under 5 V
• Dot matrix shows lines or lights solid, and no CPU lamps work
• DMD shows lines or garbage and no controlled lamps light
• CPU won't boot, 5V collapses under load: replaced bridge not joined on the top side
• Won't boot, only some lamps on: bad capacitor joints on the power supply board

Source: Repairing DataEast 1987 (Laser War) to Sega 1995 (Batman Forever), Part Two, Clay Harrell (pinrepair.com)