Hi to everyone, i've recently been given a HP-22 (which i'd like to sell) but i don't know if it's working ok. Could anyone tell me if there's a self test for this model? So far i've only found one for the HP-22S and i can't see it in the "notes" as mentioned on this website.


Before it's too late: if you have the mains adapter, don't use it! You will almost certainly destroy the calculator if the battery pack is not present, not well connected, or no longer functioning.

Sorry: I have no more specific advice to give. So far as I am aware machines in this series don't have a built-in self test. To see if it's working you'll have to power it on or sell it as untested.

What sort of state is the battery pack in?

Nigel (UK)



The batteries are slightly corroded but everything seems to work fine. My only problem is i can't find the equivalent to = and "enter" didn't seem to work. Thanks, Sue


Hi Sue,

My only problem is I can't find the equivalent to = and "enter" didn't seem to work.

Please look here.

The best thing to do to test it is to get one of those little battery holders from Radio Smack, load it with the appropriate number of batteries to reach the design voltage, and then connect to the battery terminals. This is the safest way to test it.

Testing with the original battery is not safe enough, because it could be shorted out at this point.


A shorted pack would be good (THAT at least would protect the calculator electronics). But typically, old battery packs act essentially like an open circuit, which equates to operation on the charger without a pack installed.

HP, mythical champion of "quality" design, surely did have many examples of poor design in its calculator products history.


There's definitively no self-test for this model. I just checked the manual.


IIRC, the Spice models (like HP-34C) were the first HPs with built-in self test. I always thought of that as a defect in the HP-41C-series design. Few had the test modules.


Many thanks for a definitive answer to that, i've already spent an evening searching the net for it. I was seriously surprised at the huge amount of information about calculators out there and found out this was made in august 1978. I think that was the year i first saw one in my maths class; i think i miss the red displays!


Everything they told you is right.
Now: the calculator really wants about 2.5 volts, as in 2 rechargeable AA cells. It can usually take 3 volts (2 alkaline AA cells) but it's safer to use the nicads or NIMHs ---- or test it with some used, not new, AA alkalines.
I didn't notice anyone telling you about the polarity. Hold the calc like you are going to use it. Turn it over. The contact that is on your right is positive, the left is neg. Or you can look at it as: they are off-center so the contact that is closest to the edge is the neg one and the one nearest the middle is positive.

Don't screw this up.

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