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HP Forum Archive 01

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30-series repair tip/schematic needed
Message #1 Posted by Viktor Toth on 1 July 1999, 5:49 a.m.

I have a non-working HP-33E in my possession that was the most corroded calculator I've ever seen, due to dead NiCads left in there to rot for years. I've cleaned up the unit but it doesn't power up; it appears its DC-DC converter is the culprit.

Since the DC-DC converter appears to be built from discrete components, it should be repairable. Trouble is, the transistors (?) all seem to have proprietary HP numbers, and even if I manage to trace the circuit, I don't know what its output voltages are supposed to be.

Can anybody help with a schematic, suggested replacements for the transistors, or any useful advice? (I'd also gratefully accept the donation of a functional DC-DC converter from any dead 30-series calculator, hehe.)

Note that this 33E is of the original design, in which the chips are held to the flexible circuit board by pressure. (I don't know whether the DC-DC converter's design remained the same during the lifetime of this series.)

Thank you for any help/advice!


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