HP 41CV calculator repair of bad battery contacts

HP made the battery contacts out of thin copper foil stretched over formed hard plastic. Seems inevitable that it will fail. I repaired two completely worn through contacts, one of which the copper was burned away from leaked battery juice.

[@WilliamCoggin-cy7wf]

I had an opportunity to finally get a scientific calculator when the HP-45. That was the thing for a student surveyor in the early '70s and I had been using the class equipment. Used it every day until the early 2010's. When the HP-41CV came out, I had to have it to use with the survey module in the field. I'm retired and use it to this day several times a week. Love it. All they need is fresh batteries every 5 or so years and the contacts wiped off if I don't feel I got enough batterie life. I did get an HP-48SX and outfitted it as a data collector, but it got damaged when the roof of my office came down. HPs have been a powerful tool for me for 50 years. I could do survey calcs all day long still, but I'm retired. I hope that you enjoy that HP because I most certainly do mine after all these years. Nice find.

[@joseph_donovan]

Wonderful to see you successfully restore this classic and much-loved, and missed, calculator back to life. Loved your solutions, too. Many thanks for sharing.

[@isleifoterogarcia4478]

I am happy that you resurrected this wonderful calculator, their weakness are those film contacts that were corroded by battery outgassing. The screws guides that held the case together break from posts when the calculator falls and received a hard knock. Also overtighten the screws break them too. This calculator is one of the last good calculators that HP made that went into history as one of their best products.

[@padraicmcguire108]

Replacement flex circuits are readily available to do this job well. Your fix though is quite ingenious. To fix the broken bosses. Most folks wrap the boss with fine electrical wire and drop some cyanoacrylate glue in the hole to tie it together. The integrity of the screw bosses is important as they need to supply the clamping force to ensure contact between the flex pads and the motherboard pads.

[@MoTown44240]

For the screw, if you really want it to fit tighter, you could a carpenter's trick. Put something in the hole that the screw threads will bite into. Maybe a sliver of toothpick. Just a sliver, not the whole toothpick. I wonder if copper tape has enough conductivity to work. If the adhesive backing isn't sufficient there always super glue.

[@cuban9splat]

Nice repair job. Hope you can find other modules you can plug into the calculator. Perhaps an electronics module with all the resonance, impedance, etc formulas. Big thumbs up!

[@homermunoz7735]

Nice fix!!

[@samuelsmith6573]

Great fix! Thanks for sharing-73,WB5PUN

[@artl52]

Nicely done Kevin. I've been an HP calculator since the 1970s and have everal in my collection. On of which is a HP-41 (my first) that I got in 1982. The battery posts are destroyed due to leakage. I wonder if it could be repaired?

[@loughkb]

You could probably repair them in a similar fashion. It's tedious to do, but worth it if you want to preserve the device.

[@ri3cjoh]

The "C" I think means it has the higher memory on board without the plugin memory. Dave talks about it on EEV on an episode. #573 or #582 I believe.

[@bennylofgren3208]

No, that would be the "V". The original was the HP-41C and the HP-41CV has the extended memory. The HP-41CX has the extended memory and a built-in module called X Functions that was a separate plugin module in the other versions.

[@jeanlemire2681]

Hi folks. The C means "Continuous Memory".

[@homermunoz7735]

I was removing the battery pack on an HP 41CV and a small thin V shaped piece of metal popped out. I believe it is a spring, but don't know where it goes. Any ideas? Thank you.

[@1djbecker]

It is likely the Battery Retainer. There should be two of them in the N cell battery pack, with each holding in two cells.