HP-65 1333A04841 restoration it doesn't work anymore ...

[Maximilian Hohmann]

Hello!

I wouldn't have worried much about the sound of the card reader. This is very much like my Ti-59 which I got in 1979 and which still works today. With the same modulated sound.

My guess why it would not read and write after the gummy wheel change is that one of the connecting cables to the card reader board broke during the disassemly and reassembly. I would have started troubleshooting form there.
This alone does of course not explain the erractic display that it shows now. Still the chances are high that this is caused by a faulty solder point or PCB trace rather than a defective ROM or something similar. Some weeks ago I was able to fix a broken Casio (a rare-ish AL-8S with DATE functions) by „beeping“ every single PCB trace until I found the one that was corroded through, invisible under the protective green paint.

Don't you have several other HP-65s by now? You could interchange boards to be sure, but that of course always carries a risk of causing extra damage.

Good luck
Max