HP-82104A Card Reader Repair Questions

[Papymouzot]

Hi Tony,

I have a few « tools » including an oscilloscope. I have done little electronics in the past and I have as a hobby electric trains N scale and I often play with the soldering iron on tiny tiny parts ??

Caps have a very bad tendency to wear overtime, and 44 years later most of them are likely to be out of service.

I recently had to change the caps inside the battery pack at the same time I changed the batteries to NiMH new ones. The 100uF was completely dead. Next pack will be modified to have a usb c charging circuit.

I would love to learn what can be said about the tests I conducted on the two card readers giving me the card err message, and what should be tested / modified next.

I would really appreciate to have some guidance on which caps to change first, their location and specs value/voltage. They won’t be easy at all to remove and if I can change the ones which may solve my problem first it would be great ?

Thanks in advance !!!!
Charles