Author Topic: GWInstek PST-3202 Power Supply Repair  (Read 150 times)

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Offline Nebukad

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GWInstek PST-3202 Power Supply Repair
« on: May 13, 2021, 03:26:45 pm »
Hey guys!

I just wanted to tell you about a faily easy repair I recently did on a GWInstek PST-3202 Bench Power Supply.

I was completely dead - you could hear the transformer humming when switched on, but there was no beep, the fan was off, the LCD was dark and it did not communicate on any of the interfaces.

After some measurements, it turned out, the logic supply on the "logic board" behind the front panel was not reading any useful voltages.

It took me a while to figure it out - please have a look at the picture:

Some black "gunk" aka. adhesive was used to keep C209 and C214 from "flapping around in the breeze". Sadly, over the years this black gunk went corrosive and atacked all metal it touched - as can be seen where the black gunk got in contact with the heatsink at the top.
Some of that gunk found its was under C209. The copper traces are protected by the solder mask, but right around the positive pad for C209, the gunk ate away the connection between the trace and the pad. As a consequence, the power from the transformer could not find its way to the capacitor and the rest of the circuit, so the whole logic was dead. I scraped away all the black gunk, reinforced some partially corroded points with fresh solder, ran a jumper wire to the capacitor and this time used some proper silicone adhesive, to keep the caps in place.

This brought the unit back to life.

Since this type of gunk was likely used on many if not all of these power supplies, I suspect, this failure mode might be or become typical for these supplies. If it does, I hope, some ppl. find this post and might also be able to fix their units rather reasily.
 
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