Thanks Guys.
Fixed the GI!
The power supply board checked out ok - all AC and DC voltages present and pretty close to specs, though a little down in most cases.
Did a bit more research though and discovered that Zacc games (2nd generation anyway) run GI direct from transformer output(6.3vac).
Also runs through a 15 amp fuse which fell apart when i removed it. Replaced and GI now working.
