hp classic calculator charger without battery pack

[teenix]

(01-08-2023 01:56 PM)badaze Wrote:  Hello,

I have this HP 67 with a broken battery contact and it works without battery pack.

From page 312 of the HP-67 owners manual...

CAUTION
Operating the HP-67 from the ac line with the battery pack
removed may result in damage to your calculator.

A game of chance perhaps.

Assuming the charger components have not degraded over time, and it is supplying the correct power to the calculator, this is probably a warning about mains spikes and surges which will probably pass through the charger and into the calculator circuits and damage them. It might be enough that when a fridge or vaccum turns on or off, or next door is welding, or a lightning storm that a damaging spike could occur, of which the ACT chip seems most susceptible. Perhaps the battery in place helps to dampen these transients.

The other problem is that the charger is not designed to solely provide the current needed for the card reader let along both the calculator and reader, and this could also cause problems especially if the charger components are not up to spec anymore.

cheers

Tony