Beginners help

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(05-10-2023 12:34 PM)Martin Hepperle Wrote:  Concerning the HP desktop calculators line 9845/9825 etc. I would not advise to simply switch them on.

Some of them have power supplies which have a tendency to fail and then overvoltage would destroy the rest of the machine. Especially the 9825 have this problem.

Generally one should always test the power supply of such old systems outside of these machines to make sure they work as advertised.
This means removing the power supply, adding a load to it and then making tests.

If this is not possible, removing all internal and add-on boards and then powering on to measure voltages would be a compromise option to minimize the risk.

Martin

that's what i feared. it is also true that i wont be able to remove and test parts like that so i guess i will take the risk. previous owner had them revised or repaired at some poit so i hope no internal components will be in such bad shape