HP35 problem with a calculator, maybe due to a faulty charger

[Maximilian Hohmann]

Hello!

(03-20-2021 02:32 PM)aurelio Wrote:  ... actually I fed it with different battery pack aleady tested (I mean they work with other calculators)

That doesn't mean too much. I have tried it with an HP-35 and an HP-67 that happen to lie next to my computer. The same half-discharged battery pack works well with the 67 but fails to power the 35.

(03-20-2021 02:32 PM)aurelio Wrote:  I read on the forum that "this machine will work just fine without a battery pack installed. The power supply for the classic series machines delivers a filtered and regulated voltage to the electronics and a separate voltage to charge the battery pack".

Which is true only as long as the power supply does exactly what it is supposed to do. But just like the calculator, it contains 50 year old electronic componets which can fail any moment in a catastrophic way. Catastrophic from the point of view of the calculator that is.

(03-20-2021 02:32 PM)aurelio Wrote:  II'm scared that the wrong initial voltage (17V circa) in place of the 4,5 could have damaged the circuit, far away still to understand what, specifically

There are 17V across two of the terminals of a functioning charger (I just measured one of mine) so the 17V for itself is rather normal. Just try yours from a regulated power supply and see what you get. And if it is broken, at least you killed one of the least expensive classic HP calculators, unless it happens to be a "red dot".

Regards
Max