I got back to working on the A3000 board, down to point 8 on the system failure checklist, probing the data bus.
I checked all the ROM sockets continuity before and after replacing them, all seems good. Turning on the board and probing the data bus at R49 initially shows data, a 4V, and then it steadily decreases (seems like intervals of 0.2: 3.8V, 3.6V, 3.4V ...) down to a few hundred mV before it becomes indistinguishable. I also probed R50 but never managed to see any data on there.
Not really sure what might be going on here, I checked the voltage at the source and it is reading a steady 4.9V
Cheers!
Nic
I checked all the ROM sockets continuity before and after replacing them, all seems good. Turning on the board and probing the data bus at R49 initially shows data, a 4V, and then it steadily decreases (seems like intervals of 0.2: 3.8V, 3.6V, 3.4V ...) down to a few hundred mV before it becomes indistinguishable. I also probed R50 but never managed to see any data on there.
Not really sure what might be going on here, I checked the voltage at the source and it is reading a steady 4.9V
Cheers!
Nic
Statistics: Posted by nicf82 — Sat Feb 24, 2024 9:31 am