Installing 51 Custom I/O controller replacement - Galaga/Bosconian

The following shows the location of the 42pin custom IC  I/O controller "51" and the steps to replace this chip
on a Galaga or Bosconian boardset.

Note: correct orientation of the chip is essential for it to operate !

CPU board
Layout of the Galaga and Bosconian CPU board are identical


Install as shown ! Correct orientation is critical !
Pin 1 is marked on th 51 replacement


Final location in place on board