Classics calculators working with charger


I have never used any classic calculator with the charger without any battery pack inside. Reading the manuals, in same models it is said you can´t do it. Can the calculator be damaged if it is done?.


Take care!
Some such HP-25,... could be damaged.
However for instance my HP-71B worked with HP-82066B & without any battery inside.

Classics were designed to run from the charger without the need for batteries in place. Perfectly safe.

Classic models (65,67) with card readers will need batteries in place for the reader to work as the wall wart alone cannot supply enough current.

The 20 series continuous memory machines will most certainly be toasted to death by operation with the wall charger with a bad battery or no battery present. The non-C models don't handle it as well, they just take a little longer for the smoke to come out.


When I say classics I mean HP-35, HP-45, HP-55, HP-65 and HP-67.


The classic charger has two supplies built in, one regulated for running the electronics, the other is low current, unregulated for charging the battery.

That gold strap in the charge plug port is actally a switch that connects to battery to the electronics when the charger is unplugged. When the charger is plugged in, the electronics run only off of the regulated charger and the battery is connected only to the unregulated charge voltage.

The 35/45/55/70/80 are fine for use on AC alone. The 65 and 67 have a connection of the card reader chip directly to the battery. Without the pack installed, the charge voltage can be fairly high and theoretically could damage the reader chip. Since dead reader chips are rather rare, I suspect that this is not too big a problem... certainly not like dead ACT chips in the woodstock machines.

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