HP-41C - serial 2052A - Memory Lost

[Vintage63]

Good day to you all, I'm back here after some time. I nevere finished repairing the clutch mechanism on my old card reader, but every now and then have a look at it.

My current problem, maybe solved for now, is the following. I had 3 memory modules. Every time I inadvertently 'banged' the calculator on the desk it froze and I had to remove the batteries to try and get it to work again. Obviuosly the dreaded Memory Lost popped up on the screen.

I rotated the memory modules in the bays and banged on purpose the 41C until it stopped freezing.

Thinking I had finally found a safe position I rewrote the various programs I kept losing.

It did it again yesterday evening. So the rotation wasn't succesful. I tried again by inserting and banging the thing until I found out that it froze with one module only. I removed it from the slot and put away.

QUESTION: is this normal, banging and freezing, or is there something I can check on the memory module to stop this from happening again, maybe the pins on the back? Or my 41C has reached the end of its life?

NB banging means placing it back on another of the desk locations without being too careful.
Thank you
Marco

[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,

[Vintage63]

Peter, you are correct!! I tried prying open the shell at the back and on one side it separates by over 1 mm.
Tried switching it on after doing this and it wouldn't start. Fortunately when it did after a few secs it lit up and worked flawlessly.
I also added new rubber feet that I had lying in the tool case, it now looks a bit like a monster truck as these are a quite thick :-)
I'll search on the forum how to make the two shells stick together properly.
I could start by tightening the screws with a light turn but would not want to brake what is holding on to dear life at the moment :-)
Thank you
Marco

[AndiGer]

Marco,
You could try to use longer screws on the lower posts. E.g. from Classics or Woodstocks
Andi

[Vintage63]

I used a short cross screwdriver and gently applied torsion to tighten the screws by the memory bays. These turned a little bit and when they stopped turning I stopped applying torque. Not that they were very loose, maybe a bit less than a quarter of a turn. Anyway I have not had the 41C freeze on me and consequently no more Memory Lost messages. But I'm always afraid that a bang on the desktop mught trigger it again. keeping fingers crossed in the meantime. Thank you for the helpful suggestions. Have a great day
Marco

[AndiGer]

The HP41CX service manual suggests on page 3-8 to use longer screws (0624-0436) if needed. The HP41C service manual lists these as 0.38 inch long whereas 0624-0435 screws are only 0.25 inch long.
Both manuals are available at literature.hpcalc.org