At switch-on the display shows ROM versions and the start-up speech plays, but nothing else happens.

Burnt 12-pin power supply input plug stops the game booting

Cause: The 12-pin square plug carrying transformer power into the power supply (the one feeding the +5 V logic) has burnt pins. The display runs because it has its own computer and supply.

Checks

• Inspect the 12-pin input plug and header for scorching; the 6-pin ground plug rarely burns.

Fix

• Replace both halves, the board header and the wire plug, with new pins.

Unplug the game before working on transformer wiring.

Systems

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

Related tips

• Square power supply plug part numbers
• Game shows ROM versions and speaks, then nothing (burnt 3J1)
• Burnt 3J1 square power input connector
• Burnt GI pin on the Data East power supply header: move it to a spare pin
• Resets from power supply connectors CN1 and CN2
• Power supply CN4 has no key: refit it carefully
• Power supply board versions are not interchangeable
• Power supply board versions and their +5 V filter capacitors

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