Srvice and repair of HP 35 & HP 21


Is there a company, like HP, that will service / repair my HP 35 and HP 21 calculators?



try fix that calc.


Luiz (Brazil)



Are you having specific problems with your 35? Many problems that tend to afflict the 35 are easy for even a relatively unskilled person to address. If you post your problems, perhaps one or several of the many knowledgeable visitors to this Forum could guide you through a repair procedure.

Although there are a couple of simple problems that afflict the 21, it is subject to some relatively more serious problems that require expert attention. However, it couldn’t hurt to also describe its problems for the community to comment on.


Happy to fix your 35 if you don't mind sending it to Australia...

I first repaired calcs and desktop computers (at the component level) for Canon Australia in 1985...

If interested write to me
(detailing the fault and how it got that way)


Don W


Happy to fix the 21 too. If it can be fixed, I'll do it...
May not be economical to repair though..

Jeff is dead right about the help you get here. Great bunch of ppl.

Luiz was able to tell me about the battery voltage for a
printer I got off ebay (believe it or not the service docs I had
didn't mention what it was). I thought it should be 6V based on the the charger output voltage but although I have 20 years plus experience in repairs, I did not want to GUESS when there are poeple here to ASK. Luiz wrote back in 90 minutes...

I now have my thermal printer running fine (still gotta do that paper feed roller, though...)

If you want to fix it (35) yourself, (1) get advice on disassemby
first and (2) get advice on and take steps to AVOID DAMAGING the


Don W
P.S. I had a friend in high school in the late 1970's who disassembled his 34C (then kinda state-of-the-art). On that machine
the chips are pressure connected (no soldering...[dumb]!) and when he got the case apart all the chips flew in different directions...
He never got it working again... He then bought a 41C...

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