Pac-Mania repair log #3

Got for repair from USA this Pac-Mania PCB on Namco Sytem 1 hardware.System is made of a larger ROM board:

And a smaller CPU board:

It booted to an ‘EEPROM ERROR’ message screen followed by some digits:

The EEPROM is a 2816 (2k x 8-bit) device located on CPU board:

I didn’t try to replace or swap this EEPROM since I knew it was not the cause of error.From my experience this is due to another IC that goes bad very often.I’m speaking bout the custom ’64A1′ located on ROM board @M4.Mine, indeed, was marked with a pencil as ‘BAD CHIP’ :

Technically the custom ’64A1′ is an HD63701 MCU in disguise with the exception of two custom opcodes.I already explained in a past post of mine how to replace it with a standard HD63701 MCU :

Namco System 1 custom ’64A1′ replacement

It’s what I did and this was enough to fix the board completely.Job done.