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A current issue with batteries for my HP-35 and HP-67 calculators
05-28-2020, 01:03 PM
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RE: A current issue with batteries for my HP-35 and HP-67 calculators
(05-28-2020 02:42 AM)johnhaley Wrote:  Hi everyone,
I’d like some help concerning a current issue with batteries for my HP-35 and HP-67 calculators. I’ve been using battery packs marketed online by Mark Hoskins and been very pleased with their performance, but he has recommended me to this forum for tech help.

Some history, in case it’s important:

Both calculators use the same battery pack, so I bought one for each of them in August 2015 (usually good for at least 3 yrs, which has been found to be true). In case it matters, the 35 was bought new with its charger in 1974. The 67 was bought new with its charger in 1979 and was refurbished by HP when its card reader wore out. It’s been my experience that the 35 will function without the battery installed when used on the charger, but the 67 MUST have the battery installed even when using the charger

Thanks

Is the behavior you reported using the same Power Adapter, or is each machine using its own separate Adapter? If the former, then the issue is in the 67 and other more knowledgeable folks will offer specific insights, but it will likely need surgery.

If each is using its own charger, then the 67 charger likely has a problem, or possibly a damaged cord. The classic chargers provide 2 types of power, one for operating the unit, the other just for charging the battery. It's possible the former is dead but the latter is still working, which is why the battery must be installed to operate.

If you have a multi-meter, check the voltage from the leads, they are marked on the connector, the center is (-). The (+) lead should be about 15V and the unlabeled lead about 5V.

--Bob Prosperi
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RE: A current issue with batteries for my HP-35 and HP-67 calculators - rprosperi - 05-28-2020 01:03 PM



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