HP-10 disassembly/reassembly

[[kby]]

Abstract: CPU confirmed to have issue.

I finally had time to get to this and had also figured out in the intervening months how to actually take measurements. I realized I could put the machine together except the keyboard and use jumper wires to connect the needed pins between the keyboard PCB and the CPU pcb. This allowed me to run the calculator with the shell open. Only the pins that are necessary to jumper needed to be done, so about
a half-dozen and I could have gotten it down more if I wanted.

The trace can be viewed here (machine is not up all of the time, unfortunately):

https://pdp-10.endoftheinternet.org//~[k...esktop.mp4

As an additional experiment I fed the output from the problem keys to a different keyboard line and got the expected (wrong) numbers entered (in this case 3 and 6 rather than 2 and 5; 2 and 5 are the non-registering keys. I tried the other way, too; using keys that work and mapping them to the 2/5 inputs; no entry. The display does flicker, but no digit :-(.

Does this pretty much confirm that the CPU is bad (seems to me like most likely issue would be the pin is disconnected from the actual silicon).

I might also eventually have to deal with a faint printer, but I might have enough spare parts to fix that.-kby