I've got a project Black Hole with a dead MPU and there doesn't seem to be much in the way of "deep dive" guidance out there.
The MPU's clock and reset sections are good, as the 6502 pulses low-then high on pin 40, and pins 39 & 37 pulse the clock. The RIOT chips pulse the same clock. But the CPU IRQ is locked high. And going from there points in many possible directions.
I understand several years ago that Ed G-P-E made a fantastic little troubleshooting board called the "Quickscan80" to narrow these scenarios down, but these are NLA. Does anybody have one they wouldn't mind parting with? Either to sell, or even loan? I'm reasonably competent board tech as I've extensively rehabbed and rebuild numerous WMS Sys6/9/11, GTB sys3, and Bally -35 boards with success. But I'm far from an expert and this is my first System80.
Still, I can assure due care to anyone who might consider loaning (renting) me their Quickscan80. But if purchase is my only option I'd consider that too.
Please LMK if you can help. Thanks!