15C short battery life

[paul spiro]

I recently replaced the batteries in my trusty 15C for maybe only the 3rd or 4th time since new. When I picked it up a couple days later it was dead. Another new set of LR44's went dead after about 3 hours of occasional use. I never noticed it getting hot or any other abnormality.

I've searched here and elsewhere but this doesn't seem to be a common problem. Any comments, suggestions?

I love my long-term companion and see it's irreplaceable except on the collector's market. And my 41CV just recently took a dive too...

[Steve Simpkin]

No one has responded so far so I will give it a shot.
My first suggestion is to buy a new set of batteries from a different source, just in case of a bad batch.
I this doesn't help, I would perform a full memory clear using the ON and - keys as described on page 64 of the Owner's Manual. You could also run the self test routines (page 263) to see if they turn up anything.
If nothing else helps, you might have a leaky tantalum memory capacitor. This is the large blue capacitor (near the battery supply wires) shown on the left side of the following picture.
http://www.hpmuseum.org/10cmbb.jpg
Obviously replacing this is a last resort.
Good luck.

[paul spiro]

thanks for the response, Steve. The 2 sets of batteries were different brands from different stores and tested fine before installation. The cont memory was already cleared from sitting w/o batteries for a few days but I threw batteries back in and ran the ON/- and ON/x tests anyway.

however... the ON/x test showed that the bottom 2 vertical elements of the penultimate right-hand digit were missing. A little experimentation revealed that unless those final 2 digits were displayed all seems fine. As soon as I display the last digit or two the display noticably dims. I'm thinking my problem is not the power capacitor but an internal short in the LCD display.

I'm going to try running the calc w/o those last 2 digits and see if that solves my battery drain. I don't suppose parts are still available? (I was hoping it was just the cap...)

Edited: 10 May 2010, 8:42 p.m.