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PANAMATIK · (This post was last modified: 01-06-2017 03:39 PM by PANAMATIK.)

(01-06-2017 09:23 AM)Paul Dale Wrote: Am I on track here or way off the mark?

Perfectly on track!

The average charging voltage behind the diode with the original charger is 3.3 Volt when the calculator is switched off and about 3 Volt if the calculator is switched on. Thus a regulated DC voltage between 3.0 - 3.3V (+ 0.6V diode drop) will work and will not cause damage to the circuits when batteries are removed.

if batteries are removed the original charger applied an average of 6.8V to the power supply circuit. This caused damage to the chips.

Keep in mind, that these voltages can potentially cause overloading of the batteries, if applied too long.

see Jaques Laportes video

Bernhard