HP-41 Buying Tips



#11

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.


#12

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.
1111


#13

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.

#14

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...


#15

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.


#16

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.

#17

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.


#18

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?


#19

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)

#20

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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