Since my Sea Scare PCB set died (again), I decided to see if I could pin-drive 6502 to investigate it:
I managed to get the ROMS to read reliably but the RAM isn't reliable. The hardware on this board uses a clock synchronized strobe for the RAM writes, and the video display is hidden synchronously in the first half of the 6502 cycle. Since the tester is asynchronous to the input clock, no chance of it working properly on this platform
However, more conventional 6502 hardware might work OK. I didn't really need it to fix this board since the chip selects were all bad due to a bad 7442, clearly visible on a scope.
A bit better luck with the tester on Z80 and Jackrabbit:
This one the speech died so I'd assumed that it'd be the speech board and I was only trying out Z80 because it was on the bench. However I noticed that the game music was wrong and some other sound effects were wrong. Poking the sound latch with the tester did generate some speech and the tester made it very easy to see that there was a stuck bit on the sound latch. So far the tester works mostly fine on this platform.
Paul.
