Enough to make you cry.

[burkhard]

Quote:Even if a battery is installed, the calculator circuitry can be ruined if the battery is bad with high internal resistance or makes poor contact with the calculator terminals. My rule is to NEVER connect the AC adapter to the calculator, and recharge the batteries externally.

Amen. You are very correct.

Really this is the safest course: Tie a tag on the charger that says "For historical purposes only. DO NOT use. Only charge batteries for HP model calculator 21, 22, 25, 25C, 27, 29C outside the calculator. Using this charger can damage the calculator", and then box it away for your heirs to find someday when they are sorting though your hoard.

I think a lot of the wasted ones come up on eBay when somebody cleans out departed grandpa's stuff and start plugging what they think is an adapter in to "See if this old junk still works".

It was a really terrible design feature even back in the day when everything didn't have to be "idiot-proofed".

burkhard