HP80 battery pack voltage reversed

[Jeff O.]

(11-03-2016 11:28 AM)elgin113 Wrote:  When I pluged the charger in it turned on OK and worked but an hour later the screen was blank.
Is the calculator permanently damaged or can it be repaired?

To be clear, you put the pack in the calculator and plugged in the original charger? If so, you probably have done no damage to your calculator, but the charger may have been damaged. Classic chargers have two circuits in them, one regulated to about 4.5 Volts to power the calculator, and another circuit which charges the battery. When you plug the charger into the calculator, it disconnects the battery from the calculator circuitry and provides 4.5 Volts from the charger to the calculator. The battery gets connected to the charging circuit of the charger. So when you turned it on, the charger powered the calculator, but by an hour later, perhaps the load of attempting to charge the reversed batteries had killed the whole charger.

There is probably a schematic available on this forum to help you determine if there is fuse or other repairable component in the charger.