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Old 03-02-2021, 10:25 PM   #4
Badcaps Veteran
Join Date: Dec 2010
City & State: Alberta
My Country: Canada
Posts: 2,024
Default Re: An old dinosaur bench top power supply - help needed

It was a trick to make a fixed voltage regulator IC adjustable by putting a pot in series with its GND pin. So you could get 5-30V depending on the transformer voltage. It has a 50V filter cap, IC is 35V in max. Similar schematic below.

For the size of this, it needs much better heatsinking something I would add to the back panel. It won't make 1A for long without heating up too much.
If the IC has failed, I would convert it to use a LM317 on a heatsink at the back.

Why is the resistor burned on the brown wire?
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