Thursday, July 27, 2017

Fixed triple power supply from a flea market


At a flea market, I came across a triple power supply for a very attractive price. When I brought it home, I noticed that a switch on the first section, which changed the meter between voltage and current readings, was mechanically broken. I also heard some rattling inside.

The switch was a common small switch that I had sitting in my back room, so it was a quick fix. The rattling sound was a heat sink with four power transistors, powering the third section which could deliver relatively high current but lower voltage than the first two sections. I attached it to the standoffs, which was all that was required. 

Testing showed that all sections worked properly, including their current limiting circuits and overvoltage protection. This will be a very useful bench tool that I acquired for $40 plus a few minutes replacing a switch and attaching a heat sink assembly internally. 

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