HP-21 - Crazy numbers

[BusyCalc]

Hello Alberto,

in my case I didn't have an oscilloscope to check the signals. I only could see that reading cards wasn't a problem (after restoring the gummy wheel, of course), but recording wasn't possible.

I cleaned the cards with isopropyl alcohol, I inserted the cards as smooth as possible, etc. with no result.

I read that the calc needs more power recording than reading and that a fully charged battery pack is desirable to do this. So, I fully charged the batteries in an external charger (I use 3 Ni-MH AA) and I got then about 4.3V.

After 2-3 unsuccessful attempts of recording, it started then doing it properly. I suppose that the caps were reformed after some use.

Were you able to check the caps of the reader/writer amplifier?

Regards.

Oscar