Check the 5C socket contacts

The address and data lines reaching the EPROM socket at 5C are the one place a bad connection can hide after the buffers test good, because the EPROM sits in a socket. Inspect and if needed replace that socket.

Systems

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

Related tips

• Replacement CPU board won't boot with the old processor: socket contact

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