Tektronix PS2520 triple output power supply repair and calibration

[feedback.loop]

Check out this video. These supplies aren't bad at all. Two channels 0-36V up to 1.5A, the third channel 0-6V up to 3A. I saw good ones on eBay for less than $150.
It turned out this supply needed a fuse, a DAC, and a calibration.

https://youtu.be/q3bn7r77yDY

[siggi]

I recently bought one of those. Mine needed a lot of TLC.
There was shorted logic on the display board, which took out the rectifier and fuse. Some of the optos weren't making grade on the current transfer ratio, and didn't make the logic thresholds on the far end. There was a broken schmitt trigger on one of the channels, and all the DACs were bad (shorted gate to source).
I found it ... interesting .... to find damage across all four galvanically isolated domains in the thing.


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[Len]

At 11:05 do I see you using an unlicensed copy of DaveCAD(TM)? 

[feedback.loop]

I recently bought one of those. Mine needed a lot of TLC.
There was shorted logic on the display board, which took out the rectifier and fuse. Some of the optos weren't making grade on the current transfer ratio, and didn't make the logic thresholds on the far end. There was a broken schmitt trigger on one of the channels, and all the DACs were bad (shorted gate to source).
I found it ... interesting .... to find damage across all four galvanically isolated domains in the thing.

Sounds unbelievable. What are the chances of so many components failing at the same time? It must have been struck by lightning.

[siggi]

Sounds unbelievable. What are the chances of so many components failing at the same time? It must have been struck by lightning.

Yeah, go figure.
It didn't look like it had been repaired or boards swapped either. All the pass elements were fine, and it calibrated right up after I fixed that litany.



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