Power supply CN4 has no key: refit it carefully

CN4 is a 12-pin plug carrying the 18 V lamp and 32 V solenoid supplies, and it has no key pin, so it is easy to put back one pin off to either side. Doing so instantly blows the 18 V lamp fuse or the 32 V solenoid fuse on the back of the backbox. Mark its position before unplugging.

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
• Resets from power supply connectors CN1 and CN2
• Burnt GI pin on the Data East power supply header: move it to a spare pin
• Burnt 12-pin power supply input plug stops the game booting
• Game shows ROM versions and speaks, then nothing (burnt 3J1)
• Power supply board versions are not interchangeable
• Power supply board fuses (late games)
• Z1 on the power supply is a varistor, not a diac

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