HP-41 Buying Tips


I have decided to start including an HP-41 Buying Tips in all my auctions. I'm finding more and more people selling HP-41 calculators as "like new" and "mint" that have serious problems.

So, I produced this HP-41 Buying Tips, to inform buyers.

I think I may add a comparison chart between the C, CV and CX. But my main focus was letting people know of potential problem areas.

What do you think? Anything else I should mention?

Edited: 8 July 2004, 2:26 p.m.


Great idea, can we link to it?

A problem I have seen is broken tines on the charger port cover, chipped corners on the battery case or corrosion on the battery springs.

Mike H.


I have no problem with anyone linking to the tip sheet. The more that are educated about this, the fewer will be disappointed.

I would like to avoid people using the link and simply falling back on "you should have asked", which I have heard from some sellers. I hope this educates sellers as well as buyers.

Edited: 8 July 2004, 3:33 p.m.


Possibly also worth mentioning dead or intermittent keys. I know there is a possibility of repair using a tiny wire brush, but I had a Halfnut that wouldn't respond to such treatment (dead decimal point key), relegating the calculator to the parts bin...


I've never met a mechanically sound key that could not be fixed using the wire brush technique. Sometimes you have to do it a few times (while preesing and releasing the key). It may also help to use some contact cleaner like DeOxit instead of alcohol.


David. Can you elaborate on how to fix the keys using the wire brush technique? I have a full nut CV that has a couple of keys with problem.


Usually the "1" and sometimes the "2" key like to go a bit soft on the earlier machines with the high top keys.

Also check the length of the display time out and auto-shutoff features.

Also check all the memory. I have a couple of machines with wonky RAM chips.

Also check all the ports. Sometimes one (or often pairs) of ports will not work properly.


David wrote :
"Also check the length of the display time out and auto-shutoff features."

What should actually be checked? On my three 41's the shut off time varies from 8 to 12 minutes. Is that reasonable? Also the TONE frequencies are noticeably lower on one machine, but that is the one with the shortest shut-off cycle. Swapping batteries makes little difference. Since they all seem to function fine, I assume this is all within tolerance?


A fair number of HP41 machines have problems where they shut off after anywhere from 0-30 seconds. Some never shut off. Also some display modules only display while a key is being held down (many times caused by old solder flux on the CPU or display or contamination on the keyboard)


Tone is dependent on the internal clock frequency. The internal clock frequncy is determined by a simple condensator with a tolerance.
In the past I used to speed up HP 41 machine's to 175% of the normal speed, consequence was next to a higher power consuption also an linear increase in tone frequency.

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