HP-41C - serial 2052A - Memory Lost

[PeterP]

Marco, one suspicion is that it has nothing to do with the memory modules, but with loose or broken posts that make the connections inside loose when you bang the calculator. I would check for that and see if e.g. the two shells separate a tiny bit when you gently pull on them or other tell tale signs of broken or loose posts.

If that turns out to be the problem, there are numerous posts here, a HP-41 calculator repair book, etc to help you approach the solution of the problem.

hope this helps,