AC Adapter for old HP Calculators


Hello all,

anybody has got an idea of how to assemble (or if there is something I can purchase in a normal electric store) an AC Adapter for an HP 67 ?

Perhaps a normal AC Adapter with the right output voltage and Amperage will do, but what about the contacts, the ones in the HP 67 are not the normal ones every AC Adaptor has?



No, there isn't.

Assuming you don't want to buy the real thing on ebay, your best option is to rebuild (if necessary) your battery pac and keep charging it on an external charger. Another option is to get a *regulated* 3.6V power supply capable of sourcing at least 1A and connecting that to the battery contacts (inside the battery compartment, NOT the AC adaptor socket.

Remember that you MUST NOT run the card reader on AC adaptor power only; you need a charged battery in the calculator for that.


Hi there and thanks for the answer.

I have a battery pac I've bough so Im can try the procedure you described, but isn't there the risk of overcharging it ?


If you want to build your own charger, the schematics can be found on the MoHPC DVD to be ordered from this website. The three contacts you need to connect to the calculator might be salvaged from connectors you find in the junkyard (or ordered new). Outer diameter of the male part is 2.0 mm. It is not impossible to find a suitable female connector assembly. Cut it open and get the individual contact elements. Combined with a small printed circuit board they fit perfectly to any Classic HP. Beware to double check the voltage / current / polarity. You may damage your calculator if you make mistakes.


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