The PIA LED comes on, goes off, comes back on and stays on; blanking never lights.

PIA LED lights, goes out, then lights again

Cause: The RAM at 5D is bad (6264, 28 pin, or 6116, 24 pin).

Fix

• Replace the RAM at 5D, fitting a socket.

Systems

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

Related tips

• CPU still will not boot after the basics
• Battery voltage at the RAM but memory still lost
• No sound, only amplifier hiss with the volume up
• Replace a failed 6116 RAM with a 6264
• The CPU memory battery is built into a non-socketed RAM chip
• Logic chips worth stocking
• Game stuck showing the last four high scores
• Game resets every two seconds

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