Using both flippers at once makes the display restart, showing its ROM revision and playing the power-on sounds, while the game keeps running.

Large display restarts when both flippers are held

Cause: The +5 V to the display controller sags under load because of worn connectors or a loose ground strap.

Checks

• Measure +5 V at the controller while holding both flippers.

Fix

• Repin the 3-pin .156" red/black +5 V plug on the controller with new trifurcon pins, or fit kit 500-6326-00.

Systems

• Data East/Sega CPU Version 3b

Games

• Batman Forever
• Baywatch
• Mary Shelley's Frankenstein
• Maverick

Related tips

• Large 192 x 64 display power connectors by display maker
• Display freezes or shows garbage after warming up: reseat the display controller ROMs
• Large display still unstable after the harness fix
• Build your own 192 x 64 display power harness
• Large 192 x 64 DMD power supply CN5 pinout
• Large 192 x 64 display blanks or resets (Sega bulletin 106)
• Setting up a replacement 192 x 64 display
• 192x64 display games have their own display supply fuse F3

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