OK time for an update.
Put the Seawitch 5101 in the Galaxy. Booted straight away and I played it for about an hour or so with no major problems BUT the high score display was all over the place (not even showing 6 digits, I can't put credits up (the under machine credit button won't work), and I can't 'pop' the game with high scores or scabs. I can play it though and it's not resetting, and G.I. is hooked up and working
Anyway getting closer, it still has the original chip sockets, so i'll replace the 5101 socket first and go from there. Also, where do I buy these 5101 chips?? Cheers guys!
