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I have an old HP-12c I used when I was in Real Estate. It's been sitting in a drawer for the last 10 years. Recently a friend of mine needed a calculator to use in his Real Estate business so I dug out the old 12-c and bought a new set of batteries for it expecting it to be "good as new"

When the batteries are in, the display remains at 0.00 no matter how many times I try hitting the ON button.

I hate the idea of just junking it, as I have the manuals and a complete set of tapes on how to make the best use of it plus I love the old clunker and I'd like to past it on.


(1) Is there something I'm doing wrong?

(2) The batteries are Energizer 357's are they possibly the wrong type? Frankly when I replaced them I just assumed the guy at Radio Shack was selling me the right ones.

(2) If it's just broken is it worth repairing and if so where?

Thanks for any help or suggestions in advance.


You got the right batteries,I think the keyboard is causing the problem,one or several keys are stuck.Try blowing on the keyboard or hit the calculator just hard enough to release the key or keys that are stuck.Good luck.


what recently helped me, was to shorten the battery contacts with a short cable (wihout the batteries in the calculator) to unload the build-in capacitor.


Andreas is right but the proceedure in the manual specifically mentions shorting the battery contacts briefly with a paper clip *with the cells in place* (Briefly is <1/2 a second) Though I doubt it makes much difference it is a little less violent to the circuitary. What happens is a static charge builds up in the machine, shorting the contacts dissapates this.