HP-41C troubleshooting Questions

[Craig Bladow]

I have two HP-41Cs that are in need of repair. The answer may be to steal the logic board from calculator B and place it in calculator A but it would be nice if both could be made to work.

Calculator A:
Does not save shifted or un-shifted key assignments, GTO .. results in a PACKING message that does not go away while XEQ PACK returns quickly. Can enter programs but the calculator locks up when run. Calculator accepts SIZE 063, data registers 0-12 pass manual tests. Setting and clearing user flags does work. No corrosion, this is my original 41C from Christmas 1980. I did pull the battery pack and also discharged the Vcc and Vbat capacitors with the problem persisting afterwards.

I'm thinking this is either D/S 0 or 1 RAM chip failure but don't know what test would isolate the problem if it is just one chip. I do have a wand if there is a synthetic command that would help.

Calculator B: While pressing keys the display may be corrupted but the X register is not affected. Sometimes the alpha register is affected. Most prevalent when the ALPHA key is pressed. This may be a zebra connector problem, any thoughts?