HP97 The journey begins

[teenix]

(12-07-2023 02:42 PM)Jonas Sandstedt Wrote:  Thanks for the quick reply Tony!
I just wonder if using the original charger might damage the ICs as in the original Woodstock design, i.e., should my re-chargeable batteries be charged outside the calculator?
Best regards Jonas

All the processor circuitry is isolated from the battery directly. The input to the CPU board should be ok up to about 16V. (Capacitor rating)

It may be a problem if the battery disconnects while on charge. There is up to 25 ohms resistance in series with the charger output, but I don't know the no load output voltage of the charger.

A 12V zener diode between the output of the high charge resistor and GND could be used to shunt excess voltage. It could be patched into the circuit board.

The safest bet is always external charging, but the decision is up to the owner.

cheers

Tony