HP charger 82002c for handheld calculators

[Dave Burson]

I was gifted with a box of small transformers and among them was a 82002C charger which can be used with the HP-35, 45, etc. This has a 3 pin output and meters a nominal 5 VDC between center and right pin and nominal -17 VDC from center to left pin. The 5 volt side makes sense but is the other voltage an indication of a bad circuit? The label says that the output is 50 MA at 4.2 VDC and 150 MA at 4 VDC. Obviously I'm in over my head here, so any thoughts would be appreciated. I'm only pursuing this because these things seem to have some value. Thanks, Dave

[Gerson W. Barbosa]

Quote:

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This has a 3 pin output and meters a nominal 5 VDC between center and right pin and nominal -17 VDC from center to left pin. The 5 volt side makes sense but is the other voltage an indication of a bad circuit?

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Please take a look at HP Battery Information, in this museum.

Quoting from the linked page:

"The battery charger circuit is current limited and will typically read much higher than 4.2 V without a load."

HTH

Gerson

P.S.:
Classic Charger Schematic

Edited: 19 May 2013, 2:14 a.m.

[Dave Burson]

Thank you Gerson, I didn't expect such an on-spot answer. It looked like those paragraphs were written just for me. Much appreciated!

(BTW, I fathered only girls, but had considered that if I had a son I might have named him either Gerson or Thurston. I thought Gerson Burson would have a memorable ring.)

Best regards,
Dave