GI stays off, or stays on when the game should turn it off.

GI will not switch on or off: power supply relay RY1

Cause: The GI relay RY1 on the power supply board, driven by CPU TIP122 Q28, commonly has cracked solder joints or contacts melted together.

Checks

• Inspect the relay's eight solder points.
• With power off, check that the contacts open and close.

Fix

• Reflow the joints, or replace the relay with the correct 24 V DC 10 A double-DPDT type.

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

• Burnt GI traces on power supplies of Time Machine and earlier
• General illumination dead or dim
• Power supply board versions are not interchangeable
• Power supply board fuses (late games)
• Z1 on the power supply is a varistor, not a diac
• Power supply board versions and their +5 V filter capacitors
• Power supply CN1 pinout, pins 1-6
• Power supply CN1 pinout, pins 7-12

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