HP-15C: too short battery life...


Hi all.
I left my HP-15C in my desk's drawer for a week (I had put fresh batteries a couple of weeks before) and when I came back to my office, the calc did not turn on: the batteries "seem" to be discharged....
Considering the proverbial duration of the batteries in the Voyagers, that sounds really strange to me....
Anyone can give me a hint on what could have happened?
(By the way, my 15C has "lost" its metal bezel around the LCD display. I measured the dimensions of its "mark" on the plastic case and I sketched a CAD drawing; then I passed it to a CNC facility in my company and I'm waiting for their "product"... I'll keep the forum updated about the result!).
Thanks in advance.


Hi, Giancarlo;

Have you tested each battery separately? Chances are that only one of them is actually bad. It happened to me once (as I remember now) a mix with good and bad batteries. I replaced the old ones for new ones and the flashing asterisk remained there. So I tested each of the 'known' new ones and I realized that one of the old, exhausted ones was placed back. After identifying the actual good ones, the calculator (an HP42S) was working happily with three fresh batteries.

Just one tale of mine…


Luiz (Brazil)


I have an aluminum bezel I removed from an old and defective 11C (I was given it yesterday). Only the metal bezel, as the HP logo and the plastic display protection are missing. The metal has to be polished or brushed, but it may do well as a temporary solution. I could send the bezel to you for free, if you're interested. Just e-mail me.


No, this is not an 11C with a memory expansion (it shows line 988!), it's just a defective one :-)

It had an intermitent failure I tried to fix it but I ruined it even more.





Wondering if you have actually polished a 15C bezel, and whether everything turned out ok? Also if you have done this what did you use? Semichrome or some compound like this. I thought these bezels had a coating that would be difficult to polish and have good results, unless the entire bezel was removed and the whole thing polished, which for me would be a risk that the bezel would not be able to be re-installed flawlessly.



Hi Forrest,

Yes, I polished my 15C bezel, but only because it looked badly. I used an abrasive polisher, (don't know how this is called in English, it is a card with abrasive particles glued on, I used the thinnest one available). I did not remove the bezel, I just protected the the display and the rest of the calculator with self adhesive lable. I used a liquid aluminum polisher for finish (Reckitt Benckiser). Instead of the brushed aluminum bezel now I have a blazing polished bezel. I know some people apply the protective coating again after polishing, but I prefer it this way.
Too bad I ruined the plastic part over the display when I tried to remove some spots of the lables's glue that had stuck on it. I made another one out of a blister package
but I was not pleased with the result. Fortunately I found an old 11C and have just made a transplantation (the photos are not good).

I don't advise polishing the bezel, unless it is too bad.





Hi, Gerson; tudo bem? (is it everything fine?)

About this:

don't know how this is called in English, it is a card with abrasive particles glued on, I used the thinnest one available
If I am not wrong with the term and with your description (lixa?), wouldn't that be 'sand paper'?

About the process: based on your description, depending on the sort of resources available yours is a very good one, surely the best possible with what you have. I have an HP15C that is a truly 'frankenstein': the PCB + case come from an HP11C, the keyboard faceplate was removed and transplanted, comparing the two aluminum bezels the best one chosen I painted with dark metalic gray (spray) and the LCD protection was the best one from the two, too. The fact is that the LCD protection has some sort of coating that greatly enhances the readability, maybe some polymer or silicom compound. I tried many others and found none with the same transparency and lower degree of reflection. It is actually amazing!

And congratulations! Your HP15C looks fine, never mind the photo quality (looks fine to me, too). BTW, what's with this photo? Are you 'hacking' your HP15C?

Té +.

Luiz (Brazil)

Edited: 7 June 2005, 12:42 a.m.


E aí, Luiz?

Thanks for your translation (I tried three or four online dictionarys and coudn't find any), 'sand paper' (lixa). I used 'lixa nº 1500'. I once suggest a collaborative multilanguage dictionary for terms like that...

BTW, what's with this photo? Are you 'hacking' your HP15C?

If you take a closer look you'll see it's an 11C, a defective one. Sometimes it allowed lines like those...
It was just too good to be true: an 11C with up to 999 programming steps! :-)


It really looks good to me also. Besides sandpaper there is an emery cloth that might work but I was thinking more like brasso that is used for cleaning and polishing military brass except I think it has amonia in it. Maybe silver polish or something.

Most of these calculators have scratches and marks that could benefit from a re-surface treatment. The protective display plastic is a problem. Too bad the label adhesive came off. A light oil might have softened it then clean the oil with a liquid glass cleaner.

I have a 71 that has the protective display plastic damaged by someones too harsh polishing, and I wonder if there is some abrasive that is so fine it would replace the glass like finish. this display is so bad that I will probably experiment. Somewhere I have heard of such a polish that can create the glass like finish.

Thanks for sharing your success.


You might try toothpaste. It contains a very fine abrasive. I've used it to remove scratches from CDs.


Brasso is actually the trademark of the product I used. But I don't think it alone can remove the remains of the protective lacquer coating on the bezel.
Before replacing the protective display plastic for the one I obtained from the damaged 11C, I had been using a piece of plastic from the HP-12C blister packaged, so I could say the calculator still had only genuine HP parts :-)

(That's an old 15C I purchased in 1984 and had been with my brother until early March)

Possibly Related Threads…
Thread Author Replies Views Last Post
  HP Prime - Short "learning" modules CR Haeger 1 1,362 11-27-2013, 02:13 PM
Last Post: Jonathan Cameron
  I have written a short introduction to the HP Prime Michael Carey 7 2,839 11-18-2013, 08:04 PM
Last Post: Michael Carey
  HP-65 short circuit Ignacio Sánchez 2 1,573 10-22-2013, 08:27 AM
Last Post: Ignacio Sánchez Reig
  Repaired HP-97 card reader doesn't show any signs of life jbssm 6 2,674 02-17-2013, 03:15 AM
Last Post: Alberto Fenini
  FRAM71 for HP-71B, short update #3 Hans Brueggemann 15 4,054 01-20-2013, 10:22 AM
Last Post: Jerry Raia
  shelf life time of a ROM, EEPROM, EPROM vs Mask Rom Guido (Canada) 6 2,987 01-11-2013, 04:09 PM
Last Post: Thomas Falk
  dm-15cc battery life David Griffith 7 2,386 12-04-2012, 10:07 PM
Last Post: Walter B
  battery life and the 50G Al 4 1,726 11-23-2012, 06:23 PM
Last Post: Chris Randle (UK)
  Battery life John Mosand 2 1,189 11-11-2012, 10:55 AM
Last Post: Eddie W. Shore
  RPL long vs. short names peacecalc 5 2,040 10-30-2012, 01:25 PM
Last Post: peacecalc

Forum Jump: