HP-10 disassembly/reassembly

[teenix]

(02-16-2020 08:34 AM)[kby] Wrote:  The display does flicker on other key entries but not the bad keys. The flicker is much briefer than other calculators.

That then means pretty much back to square one I suppose. Either the signal is not getting to the CPU in a useable form, or the CPU is faulty.

I know it would be painful, but if it were me, I would solder a couple of wires, (fine wire wrap wire is a good choice) one from ground and one from the CPU pin and see the signals being generated on a scope. To me that is really the only way to find the culprit.

As the K12 line to the display is in parallel with the keys line, isolating it from the display might prove if that is a problem also.

cheers

Tony