GI lamps are very bright but fail within weeks.

GI bulbs burning out quickly

Cause: The transformer GI tap runs high: it should be at most 6.4 V AC but often measures around 7.25 V AC. Bulbs last many times longer at 5.5 to 6.0 V AC.

Checks

• With the game on and GI lit, measure the AC voltage across the yellow GI feed and return.

Fix

• Drop about half a volt with a bridge rectifier wired as described in the GI voltage reduction procedure.

Measuring at the transformer exposes nearby line voltage terminals; keep probes on the GI wiring only.

Systems

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

Related tips

• Bulb spares: #44 for CPU lamps, #47 for general illumination
• One string of GI lamps very dim: replace the bad GI wiring
• Lamps on a plug-in lamp board do not light
• One controlled lamp never lights, bulb is good
• Test each lamp column driver with a test lamp
• Test each lamp row driver with a test lamp
• One insert stays dark with good bulbs and sockets: failed diode on its lamp board
• A group of clock lamps never light with good wiring: reseat the bulbs in their sockets

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