HP-10 Adding Machine


Hi Forum,

I just picked up an hp-10 from my uncle who worked for HP. It is in need of some restoration as it is quite dirty, needs new batteries and doesn't seen to be working right.

My question is: I know some calcs are recommended to be run with batteries. Is this one of the designs? I plugged it in and the printer head initializes and the led's flicker back and forth.

Any thoughts?


You must have batteries in this machine to run this calc. It's not hard to open the battery pack and replace the 4 nicad cells with new ones. You will see exactly the results that you are getting if you run this without good batteries in it.



yup, that's the ticket. New batteries and it is alive again. Thanks for the confirmation.

Now to cleaning.

I saw some insane prices quoted on this thing on this website. Is that still true? Is it that rare to warant > $500?

I can't sell it as my uncle gave it to me, but....


It's pretty rare and might fetch around $400-$500 if it's in very good condition. OTOH, it's not RPN and some of the people on this forum wouldn't' even consider a non-RPN calculator even if HP made it when they were in their prime.

Take a really close look (using a magnifying glass) at the decimal points in the LED display on your HP-10. More likely then not you'll find a surprise.



Boys, that's intriguing ... what should exactly be revealed ? Cheers Alberto


Only one of the coolest features of any LED calculator in history. Though there are some displays in the HP-10's and 19C's without this, most have it. I have a couple of displays without it, but they're in my parts box. My working machines are spiritually correct. (Though I wonder, Katie: rarities are often worth more, but this is such an outstanding feature of the machine that I suspect the more common display is still the more important....)


I once postulated that it must be the most valuable dot in all of HP calculator history!


Take a really close look (using a magnifying glass) at the decimal points in the LED display on your HP-10. More likely then not you'll find a surprise.

Is it the microdot from Arnold Rimmer's swimming certificate?


Edited: 6 Apr 2010, 7:56 p.m.


Is it decimal point inside the digit?

I think the calculator is in pretty good shape. All LEDs work. I don't know if the printer works as I have no paper. It has the charger (with box) and an extra battery (with box). I also have a photocopied manual. Were the originals black and white?

Pictures here:



For those of us who don't have one, what can you see? Can anyone post an image? Cheers, Keith


This is one I took years ago, but there are much better photos out there.....


Edited: 6 Apr 2010, 9:22 p.m.


Huh, doesn't appear to have the HP on any of the decimal points.

Where does that place this one?



Are you sure you don't have it? You really do need to have a pretty strong (10x or more magnifying glass to see the "hp" logo. If you have it it would be on all the decimal points.

I think we took an informal survey of sorts here and came to the conclusion that about 1/4 of all the hp-19c and hp-10 calculators have displays without the decimal points. I don't recall if there's a correlation to serial numbers.



I'll check mine tonight and will post the results .... take care everybody, Alberto


Couldn't find a lens, so I've used the camera zoom function (optical 5X), and to me it's not there ...
Units tested are : HP10C S/N 1801S11736 and HP19C S/N 1801S11435 (it's funny how close these S/Ns are)

BTW, since the batteries were almost dead, I tried to charge them with an 82031A, but the HP10's display (didn't try it on the 19C), was badly flickering.

Which charger can I safely use ? Topcat's, HP41's will do the job ?
Take care everybody, Alberto


Hello Alberto,
the charger HP-82031A can be used properly with your HP-10 (and 19C, 41C/CV/CX, 91, 92, 97, 97 and if you have it, 95C) like the HP-82066A/B.
If the HP-10 is flickering, you must search for other issues.
Take care



It's not on HP-19C serial 1801A011xx.


serial number is 1802s11681


Wow, that's awesome - thanks Katie! Cheers, Keith


Ok, so should I presume this later ('78) calculator doens't have the logo, but is just as rare/valuable as one with the logo?

Is it more valuable?


That's a difficult one to answer - for me personally, I have no real interest in the HP-10, except now for the dot - but you can get the HP-dot in the 19C, so I would rather go for that one over the HP-10.

So It really depends on who is looking for an HP-10 at the time, and whether they are after a 'dot' or a 'no-dot' to complete their collection and how much they are prepared to spend. The HP-10 is a rare beast, so I would imagine that it would be valuable with or without the dot.

Cheers, Keith


Agreed, as these things can always fluctuate wildly based on "who wants it"

I just sold one of 3 HP-55's I had for $170 to a guy in New Zealand. I had listed it with a reserve a few weeks before and didn't get $80 for it. Needless to say, I was happy to get almost $100 more by relisting it.

Me peronsally would rather have the logo. That seems unique.

I tried like hell with my 10X jewlers glass and couldn't see a thing. I've got to get a higher magnifier to see if it is really there.


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