AC Charger for HP-21

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(11-15-2015 10:22 PM)Harald Wrote:  It is very much advisable to modify the battery pack to accept alkalines and not bother with the charger. If you have bad batteries or a bad contact while charging and the calculator is turned on, the supply voltage can become far to high and damage the calculator.
All you need to do is cut open the thin plastic strip at the end where the opening for the battery contacts is. Now you can push it up and to one side and slide out one battery. You will have to bend the plastic of the holder, so it is easiest to use a screwdriver do pry the battery out. The second battery will come out much easier.

Excellent! Thanks very much for your advice. Now, I will have the confidence to proceed with doing this mod.

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