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Old 03-02-2021, 10:35 PM   #5
R_J
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Default Re: An old dinosaur bench top power supply - help needed

Quote:
Originally Posted by Kg74 View Post
Thanks RJ - sounds like it may be worth some attention. I measured the transformer output and it is 25V a/c. Diodes seem to check out.

Any suggestions on testing the UA7805? Can it be done on board or should I remove it?
Just measure the voltages, the regulator should have around +35v input and the output should vary depending on the position of the control, (you can also check the ground pin voltage on the ic) The output of the regulator should ajust from +5v to around +30v If it does not, the regulator ic is likely bad.
The burnt resistor looks like it is the current limiter for the led?

Last edited by R_J; 03-02-2021 at 10:48 PM..
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