Testing my HP-91


I just got a nearly new looking HP-91 -- only, since I don't have the ac adapter, I can't tell if it's nearly new working as well. I do have a crummy Radio Shack type adapter that I could try the calc on, except I've been known to kill calculators that way. Is there any way to use one of the RS adapters that's absolutely safe or should I bide my time until I come across some standard HP issue stuff? Thanks, erik


Hi Erik, You need to use a battery as well as the correct charger. I believe the chargers are 8V AC, 3A. Does your calculator have a good battery? 4 rechargeable C cells. I have some extra chargers for sale if you are interested. Thanks


I happen to have an HP 82059D charger and from looking at the classifieds here, it seems that this might be the right charger for the HP-91. Can anyone confirm this? And if it's right, how do you insert the plug: it fits onto the HP-91 prongs easy enough both way; i.e., there's no obvious right way. Thanks, Erik


The 82059D is almost certainly the correct charger for the HP-91. (I say 'almost' because I never had an HP-91 in my hands, but I have no reason to believe that its charger is different from that of the HP-97... and that one is the 82059D.)

The polarity doesn't matter. It is an AC charger, the current is rectified inside the calculator. It is VERY important, however, to have a working battery pack in the calculator before connecting the charger, because the battery pack acts both as a regulator and a filter.


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