Bank-switched coils and flashers are intermittent or dead.

L/R relay burnt or intermittent

Cause: If Q29 locks on for a long time the relay can overheat and weld its contacts. Fatigued solder joints on the relay are also common.

Checks

• Look for discoloured relay housing or cracked joints at its pins.

Fix

• Reflow the relay joints; replace the relay if overheated.

Systems

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

Related tips

• All L or all R bank coils/flashers dead: PPB relay K1
• Several bank-switched coils or flashers dead, or firing the wrong device
• A coil or flasher comes on and stays on at power-up
• Bank select relay and CPU transistor Q29
• Use the manual's coil/flasher chart to find driver transistors
• Multiplexed L/R (A/B) banks and wire colours
• Time Machine to The Simpsons swap the L and R banks
• Testing the L/R select relay by grounding Q29

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