Life span of an HP Calculator

[brouhaha]

(09-14-2024 01:02 AM)rprosperi Wrote:  FYI - Running the card reader on A/C power only is specifically recommend against in the Owner's Handbook.

The HP-65 and HP-67 have almost the same design error as the Woodstock series. If a good battery is not present and making good connection, too high a voltage can get to the card reader circuitry. (In a Woodstock, it can damage all the PMOS chips.) I think the 97 may have the same issue. The other Topcat models (91, 92) do not. However, the 91/92/97 will not work _correctly_ without an at least somewhat good battery in place and making good contact.

The other Classic models (35, 45, 55, 70, and 80) do not have this problem.

At this late date, the general advice I'd give is to always recharge the batteries outside the calculator, and generally avoid using the calculator on an AC adapter. The 91/92/97 printers draw so much current that if you're going to print much, you have to have the AC adapter, but in that case make sure the battery is working (powering the calculator properly) before plugging in the adapter.