PPC ROM in HP-41CX

[BillBee]

It could be a few things:

Common ones:

The ribbon strip is no longer making consistent contact with the main board.

-Corrosion, broken case back (where the top screws go through the plastic gets brittle with age and can break not allowing for contact pressure).

If its a full-nut 41 it could be a lower post or zebra strip issue.
-Corrosion, lower posts.

A search of this site will bring you a wealth of suggestions.

-Bill