Hey all
I just picked up a new machine and I'm fighting a switch matrix issue. What I'm seeing is that any switch on row 0 (i0) and row 1(i1) always fire together. This also happens with rows 5 and 6. It looks like on this X's and O's the switch matrix feeds straight into a 6821.
Thus far I've tried ohming out the rows and they don't seem truly shorted, and I've also tried swapping the 2 6821s on the mpu board. I've also went through the switches looking for issues and am wondering if there are other places to focus my efforts? Is a row short likely a diode issue?
Thanks