Low-bat indication continuously on


Hi, I have an HP-21 calculator which I had in use until a few years ago. There were never any defects, except for several replaced battery packs. Because it "ate" Ni-Cads, I used it with the mains adapter most of the time, which in turn damaged the batteries quickly.

My question: Even with new cells, the "low battery" indication (inverted decimal points) is always on. I would like to fix this, because I really like the part. Still perfect for every day work, no key bouncing at all ...

Has anyone experienced the same effect? Are there any schematics of the vintage HP calculators available, which could help to find the problem?



For what its worth, had a similar experience with vintage HP.45.

Issue was solved by dissassembly of calculator and thorough cleaning of contacts on power switch.

Works like a champ now.

John Stark

PS: BE CAREFUL disasembling a Woodstock-class unit. You may want to review others' experience before proceeding.

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