No GI even though the connectors on the boards look fine.

GI still out with good board connectors: check the transformer plug

Cause: The round-pin .093 inch Molex plug joining the yellow GI wires to the transformer in the bottom of the cabinet has burnt. It fails less often than the board plugs.

Checks

• Unplug the game and inspect the four-pin plug on the yellow transformer wires for heat damage.

Fix

• Replace the pins: female 02-09-1119, male 02-09-2118, removed with an extractor such as Molex 11-03-0006.

Unplug the game before working on the transformer, line wiring or power supply board.

Systems

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

Related tips

• GI dead but the driver board connectors look fine
• Driving the Haunted House up-kicker from a pop bumper driver board
• Parts for converting an export Data East or Sega game to 120 V
• A row of lamps stays on solid, works if the plug is pushed sideways: repin the header
• A whole row or column of lamps is stuck on and extra bright

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