Power supply reverse shorted? It might not be toast...

Symbioquine

Solar Enthusiast
Joined
Jul 6, 2021
Messages
170
I'm guessing that many other folks - like me - have also accidentally shorted in reverse their power supplies while top balancing such that somewhere between -12v and -56v flowed through the power supply.

When this happened to me, sparks flew and subsequently the power supply stopped working correctly - acting shorted, dials wouldn't produce intended changes on display, and negative voltage was produced from the terminals.

I wanted to post here and share that (at least in my case) it was a fairly easy fix. I posted some photos of the internals on the EEVblog forum and they confirmed my suspicion that I needed to repair the trace that had acted like a fuse and they also pointed out that the reverse protection diode likely got fried.

I repaired the trace with some solder and lifted the diode to test it. Sure enough, the diode was fried and I now have a working power supply - albeit without reverse current protection until the replacement diode arrives.
 

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Frick

Solar Enthusiast
Joined
Mar 20, 2021
Messages
129
I had the same issue, mine was just the diode right inside the front cover across the output terminals fried into a short circuit. Clipped it out and power supply works great.
 

Symbioquine

Solar Enthusiast
Joined
Jul 6, 2021
Messages
170
I had the same issue, mine was just the diode right inside the front cover across the output terminals fried into a short circuit. Clipped it out and power supply works great.

Yeah, mine worked without the diode (i.e. after removing the old one and before adding the replacement) too, but I think there's some safety concern in operating without that diode.
 

HighTechLab

Small Business Owner
Joined
Sep 23, 2019
Messages
641
that diode is a reverse polarity clamping diode - if you do exactly what you did, it clamps the rail down to 0v so that it can't go negative and cause upstream damage
 

DJSmiley

Solar Addict
Joined
Aug 13, 2020
Messages
555
It works fine without that diode. But that diode is to prevent frying the powersupply.

It did it's job, but if you don't replace it and just remove it... the next time the supply is fried. Better install a new diode to prevent the next f*ckup to do more damage.
 
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