HP-25 not working

[Steve Simpkin]

A couple of quick notes.

1. Never plug the AC Charger power supply into the HP-25 without a know good battery installed! This will likely damage the ACT chip instantly. These models use the batteries to regulate the charger voltage. It is best not to use the charger at all. For long time use, charge the batteries outside of the calculator.

2. When using Alkaline batteries, be aware that the positive terminal of the battery may not make good contact with the PCB contact point (rivit) in the battery compartment. You may need to try it a couple of times before it works. It is best to use flat-top rechargeable batteries.

3. Observe proper polarity of the batteries as shown in the following picture.
https://www.hpmuseum.org/batts/batt20.jpg