Fixing a HP 38C

[PANAMATIK]

(03-04-2021 04:27 AM)Dave92F1 Wrote:  One thing I've learned since my original post: If I pull out the battery for 5 minutes, then put it back in, usually the first time I turn it on I get "Pr Error", then the second time it starts up OK ("0.00"). And it works OK for the first 5 or 6 keystrokes, then goes nuts again. But if I leave the battery in I get "0.00" on maybe 1 out of 20 tries. Pull out the battery - get "Pr Error" 10/10 tries, then "0.00" 7/10 tries. Something about pulling the battery helps (resetting the continuous memory maybe).

Your image shows indeed the soldered version. Therefore the failure cannot be explained by the common contact problems in the solderless version.

When the HP-38C program starts, it tests only a part of Continuous RAM and shows "Pr Error" if it is lost. Perhaps the failure is a RAM problem, but can also be one of the other circuits.

I have an HP-38C Chip set left over in my parts box, but cannot guarantee that it is working.

Bernhard