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Rainer Hofmeister · 08-12-1999, 09:48 AM

I just got a HP-97 without charger and battery pack. I want to build a 220 Volt charger for the calculator. Can this be done safely? Which one of the pins on the back is PLUS and which one MINUS? Or is this an AC adapter?

steve · 08-12-1999, 11:08 AM

I charge the rebuilt pack of mine inside an HP41 cassete drive.

Sorry, I can't help you with the polarity of the 97 connector.

DaveC · 08-12-1999, 05:30 PM

The feed to the calc is AC so polarity doesnt matter. *However* you have a problem inasmuch as the 97 wont power up without a battery pack without some internal hacking. You need 4 sub-c cells to make a pack (see elsewhere on this site for polarity) and need to feed around 8V AC at around 400mA. You could use a DC adaptor 9V at 500mA but you still need the pack!

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