HP-97 on charger only

[teenix]

(03-18-2020 08:02 AM)Moggul Wrote:  Mine did not like it at all.

When I got my HP-97 the battery did not hold any charge so when connected to the charger the calculator would disply just gibberish. Afeter I installed a fresh battery pack the calculator operated normally again.

It seems the battery plays a part even down to basic calculator operation, but probably not damaging like the Woodstocks. I would imagine it behaves as a large capacitor, when charging is taking place, to smooth out the raw rectified AC.

Maybe the large resistor on the CPU board gets a bit warm when the battery is missing or faulty as it absorbs this excess voltage and the circuits cannot work properly due to the rather large ripple on the supply.

cheers

Tony