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HP Forum Archive 13

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HP-41 Durability
Message #1 Posted by bill platt on 19 Aug 2003, 7:56 p.m.

Well, here is the qustion: Having taken the plunge some months back and bought a damaged 41CV, I now have to ask the question to the "experts":

How is the durability of the 41 series? How d oyou stack it up against the Voyagers, or the previous HP's? Or, against the Charlemagnes and Pioneers? How about differences between "Halfnut" and "FullNut?

I seem to remember soemone saying that he halfnot might be harder to break in the 1st place, but that the fullnut has better chance of repair.

Is the "cracked post" problem endemic or occasional? Does the Halfnut sufferfrom this too?

And how come I don't hear a lot of complaints about the seemingly fragile golden plastic battery contacts/expansion port connectors? Are these actually more durable than they look?



Re: HP-41 Durability
Message #2 Posted by Chan Tran on 19 Aug 2003, 8:34 p.m.,
in response to message #1 by bill platt

I damaged a 25 by using the charger with a capacitor in the battery place. I damaged a 41C (full nut) by droping it 3 ft to hard floor.

Re: HP-41 Durability
Message #3 Posted by bill platt on 20 Aug 2003, 8:59 a.m.,
in response to message #2 by Chan Tran

Hi Chan Tran,

Capacitor: What where you doing with the capacitor?


Bill Platt

Re: HP-41 Durability
Message #4 Posted by Valentin Albillo on 20 Aug 2003, 5:26 a.m.,
in response to message #1 by bill platt

Not being a hardware guy, I can only offer my nearly 26+ year experience with HP calculators. Among the ones I have in my collection:

Voyager series (HP-10C/11C/12C(USA)/15C/16C)

Most resistant to anything and everything, nearly impervious to use. Never had one broke, all have withstood heavy use with no visible effect. A particular HP-11C I used extensively for a year in the Sahara desert, while I was in the Foreign Legion, and 22 years later it still looks and works like new (now running in its 3rd set of batteries in 22 years, expect them to last till its 30th anniversary at the very least).


Another brick of a machine, I own three and all of them are immaculate and absolutely as new, one of them despite heavy use in less that safe environments. Never failed despite their age, seem unaffected by use or time.


Apart from the battery pack, which I had to rebuild, same as the previous ones: impervious to everything, looks and works as new (acquired in 1976)

Pioneer series (HP-32S/32SII/42S)

These models have also never failed at all, and they all are as new, but they are less old, and I haven't used them at any length, so I can't really compare them to the above models. They do seem quite solid and reliably built, indeed, if somewhat less than the Voyagers, the 71B, and the Woodstock series, not to mention the Classic series (HP-67, etc).

HP-41CV (fullnut)

Another model absolutely brand new. However, I've used (very extensively) a large number of HP-41C/CV/CX models, and while it's a great machine, I always had the feeling that it wasn't as solidly built and durable as, say, an HP-67, which I owned previously. Perhaps an example will help: if you take an HP-67 in your open hand, and strongly close your fist around it, as it to crush it, you'll feel that it does not crack or make cracking noises, no bending, it doesn't noticeably yield, you'll probably hurt yourself if you increase the pressure.

But if you try to do that with an HP-41C instead, you'll hear noises, you'll feel it bending appreciably, and chances are you'll actually damage the machine while applying only a moderate amount of pressure.

Spice series (HP-34C, etc)

The flimsiest of them all. However much I like these machines, their looks, their display, their innovative and advanced functionality, I can't help but feel that their physical casing is the worst, leading to many hardware failures, most specially non-working keys, etc. I think that HP tried to cut costs, but they simply overdid it and these machines aren't very durable or reliable at all, which probably explains their low popularity (except for the HP-34C, fortunately).

Finally, a special mention for the battery door and battery compartment of such models as the HP28S, which are the least durable and worst design ever (the battery doors and compartment, I mean) in any HP machine whatsoever, and the Chinese batch of HP-12Cs, which have the most unreliable keyboard ever.

Best regards from V.

Re: HP-41 Durability
Message #5 Posted by bill platt on 20 Aug 2003, 8:22 a.m.,
in response to message #4 by Valentin Albillo


Thanks for your feedback!

BTW, I broke the LCD of my first 11-C when it fell off the desk in class, back in 1983. So, I switched to a slide rule for the rest of the year while I waited for my HP to come back (it was under warranty.) It survived many a fall after that--until I lost it in 1996 on an Airplane from New Orleans to Philly.

Re: HP-41 Durability
Message #6 Posted by Pierre Brial on 20 Aug 2003, 10:22 a.m.,
in response to message #1 by bill platt

Hello Bill Some times ago a friend give me a suposedly broken HP-41CX without battery pack. In fact only the posts were cracken, and there was not enough pressure on the soft connector. I replace it with soldered wires, and now the calculator work as new. From what I see inside, the weak posts are the only major flaw in this calculator. The electronic is very hardy and standed some overvoltage I put by error during my numerous attempt to power it with external power. The keyboard is good also, and for mine, only the LN key need to be pressed stronger to work (I don't know why) There is reports of corrosion or wear of the plastic battery and ports connector, but despite mine has been intensively used by its previous owner in damp equatorial environment, I didn't notice this kind of problem. All the best Pierre

Re: HP-41 Durability
Message #7 Posted by David Smith on 20 Aug 2003, 3:07 p.m.,
in response to message #1 by bill platt

From my experience (with over 100 '41 series machines) I would say that half have some sort of post/screw boss problems. Probably half of those (25) are just minor cracks or splits that don't affect anything. I do try and fix them with plastic welding solvent.

The other half have more severe problems. Mayby 20 have broken screw bosses that keep the battery contact assembly from making good contact. The other 5 have sheared off bottom screw posts. These can be fixed but it is a pain.

An interesting thing about the tall key 41C machines... pretty much ALL of them have a "1" key that is not very clicky and a somewhat less weak feeling "0" and/or "2" key.

Re: HP-41 Durability
Message #8 Posted by bill platt on 20 Aug 2003, 4:55 p.m.,
in response to message #7 by David Smith

Hi David,

So, then it sounds like 1 out of 4 have problems that are significant and severe enough to cause a loss of function without repairs being carried out. This is interesting and significant--Perhaps even more interesting is that this calculator was the longest selling until the 12-C, yes?

I wonder how many of the 25% that are damaged, end up non-repairable?



Re: HP-41 Durability
Message #9 Posted by David Smith on 21 Aug 2003, 3:03 p.m.,
in response to message #8 by bill platt

Well, I have managed to fix pretty much all of the really bad cases... It takes a lot of time and practice. Also just about any '41 will need to be opened and have its internal contacts cleaned and probably a few key contacts also.

Most of these statistics are based upon a couple of rather large lots of machines that I bought for cheap. They are probably indicative of what you would find when buying dead, flakey, or "unknown" condition machines... or "good" ones from strangers.

Also I neglected to include the corroded battery contact failures in my numbers. Probably 1/3 of the machines have some sort of corrosion. Mayby 5 percent are basically so far corroded that they are not repairable. Another 10 percent just need cleaning and dousing with anti-corrosion goo. The rest need some surgery to mend the contacts (usually only the left most contact in the battery compartment).

Re: HP-41 Durability
Message #10 Posted by Randy Sloyer on 20 Aug 2003, 10:09 p.m.,
in response to message #1 by bill platt

What we don't see in these 41 numbers is what percentage of the total population the dead ones represent. I think you will find it is an incredibly small number, probably less than 1% of the total population. Lets remember we are talking about a twenty-year-old product here. How many twenty-year-old TI's do you still see in daily use?

For my two cents worth, the original Voyagers are the highest reliability of all HP calculators. The newer Malaysian and Chinese 12C's should not be included; they are a different animal altogether.

Second place goes to half-nut 41ís. While broken posts and corroded battery holders account for most half-nut problems, they still hold up better in rough use than any other model due to the keyboard. Full nuts have all problems David mentioned but you canít beat them for display size and viewing angle. 41íS are by far the most repairable of the LCD models.

The Pioneers and 48ís take third place for one reason: the keyboard. While the tactile feedback is great, use in dirty environments will lead to keyboard failures due to dirt ingress. Keyboards account for 98% of all non-repairable Pioneer/48 models. Also, there are a fair number of LCD failures; this is related to physical size on the 48 and rigid mounting used in all models in this family.

If you want a 41 and donít care about the differences in the LCD, buy a half-nut. Hereís my top ten list for maximum life:

10. Donít forget to change the batteries every year no matter what.

9. Donít install A23 12 volt batteries even though they fit.

8. Donít put it in your shirt pocket, even though it fits.

7. Donít sweep the eraser dirt into the keyboard (You draw on a computer???).

6. Donít loan it to a co-worker that thinks the keyboard is a manual typewriter.

5. Donít leave it in the glove box of a hot car.

4. Donít use it as a fly swatter.

3. Donít use it as the float to check specific gravity of your home brew ale.

And should it ever have a problem:

2. Donít tin the battery contacts with solder when the unit doesnít power up.

1. Donít spray the keyboard with WD40 because a key is sticky.

There is only one item above I made up. All the others I have seen in 41ís returned for repair. Honest.

Tnx, Randy! Excellent List!
Message #11 Posted by bill platt on 21 Aug 2003, 12:05 a.m.,
in response to message #10 by Randy Sloyer

And actually it is very helpful and insightful. I think the point you make about repairability is especially importatnt, too--judging from Luiz and ither's posts here a few months back, it can be done successfully! And so I must say I am finding this more fascinating all the time.



Re: HP-41 Durability
Message #12 Posted by Pieter Botha on 21 Aug 2003, 12:42 a.m.,
in response to message #10 by Randy Sloyer

Thanks Randy, good advice. Especially the SG metering of the ale ;^)

What do you experts recommend for repairing battery contacts, then ? I seem to remember somebody else having repaired them by soldering thin cpooer sheet across the contact tips.

What do you guys (girls ?) think ?

Re: HP-41 Durability
Message #13 Posted by Randy Sloyer on 21 Aug 2003, 7:03 a.m.,
in response to message #12 by Pieter Botha

Beer stories

Technically, I have seen calculators killed by beer, just not a 41. It was a 17B that was being used during an all night cram fueled by brew. The calc got soaked with suds and was left to dry, batteries still inside. A day later the keyboard was toast due to electrolysis, a common Pioneer failure.

Indestructible Voyager stories

I repaired a 15C that spent three days on a street in Vail Colorado during ski season. There were tire tread marks on the back of the case and cinders embedded in the keytops. The only fault with the unit was that the LCD locating pins had been sheared off and it was out of position. Still works today.

Battery holder repairs

I use two methods. One is quick and dirty: conductive adhesive copper foil tape. Works fine, but I would rate life at no more than five years or so. Only works in the case of minor gold tip wear damage, the kind of damage that most solder over. Ugly.

Method two yields the most robust repaired connector. This is David Smiths' fix of using 1/8" brass U channel. Cut pieces about 5mm long (less than the width of the negative terminal of a battery) that forms a cap over the damaged area. The flat bottom part of the U becomes the new battery contact. Scrape the insulation off the connector and solder to the copper foil. I use a low-temperature hard solder called Tix and an adjustable temperature soldering iron to avoid melting things. You might have to cut away some of the old copper and sometimes glue the brass piece in place first. Every damaged holder is different, it is a touchy feely kind of fix.

Edited: 21 Aug 2003, 7:06 a.m.

HP-25 football
Message #14 Posted by Michael Meyer on 21 Aug 2003, 1:06 a.m.,
in response to message #10 by Randy Sloyer

Voyagers may be reliable, but I don't think any HP was built with the durability of the Woodstocks.

When I first started collection years ago, I bought several HP-25's for about $25 each on eBay. Who knew they'd become more valuable? I used to carry one of the 25's as my "every day" calculator. Not the prettiest, of course. Now I use a 67.

Anyway, I repeatedly and confidently threw the calculator across the room (carpeted floor). I don't think I've ever seen a broken woodstock case. Actually, the 25 seemed to be MORE reliable, as far as battery contacts. I've never succeeded in breaking an HP-25. I've posted in the past what I put my high school calculator through....

I don't think any other HP... and certainly any newer, LCD calculator could survive being bounced end over end on the floor. The 25, however, is almost indestructable. I presume it's destructable: again, I've never broken one from even purposeful, brutal abuse.

I remember reading the letters to HP about calculator survival. One survived being blown through a snowblower. Another survived a whole winter buried in snow.

An amazing machine, and it doubles as a football in a pinch!

RTN2RPN Michael

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