I managed to bring this back from totally dead by replacing a lot of the acid damaged components on the CPU board. They had lasted for years but when it died again I figured is was time to try and bullet proof against them failing one by one in future. After doing that I was almost there, it would pass all Fluke tests (that you can run from the z80) start it's boot test and then get stuck on the test result screen.
Eventually traced this to the 74LS161 @ 6A on the CPU board.
Probing this pin I found it was floating. If I momentarily touched pin 2 with another pin next to it the game would continue to boot! Found this signal 128V is generated from the 07 custom @ 7M and did some continuity tracing.
Coninuity seemed to be fine up to the socket but not to the pin of the custom itself. The custom is outputting a signal so it had to be the socket was bad. Replaced the socket and the game booted. Then onto the next problem...
Eventually traced this to the 74LS161 @ 6A on the CPU board.
Probing this pin I found it was floating. If I momentarily touched pin 2 with another pin next to it the game would continue to boot! Found this signal 128V is generated from the 07 custom @ 7M and did some continuity tracing.
Coninuity seemed to be fine up to the socket but not to the pin of the custom itself. The custom is outputting a signal so it had to be the socket was bad. Replaced the socket and the game booted. Then onto the next problem...
