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Video Blog #036 - Digimess PM6003 Power Supply Repair

DISCLAIMER: This video is educational only, so if you decide to do the same yourself then you are on your own, I can't be held responsible for any problems/issues/damage/injury that may occur if you decide to follow this blog and try it yourself.


I purchased a Digimess PM6003 0-60VDC / 3A power supply from the manufacturer as faulty (beyond economical repair) and went to work to repair it myself.

Digimess schematic diagram here. Please note the diagram covers a few different models in the Digimess range, doesn't contain the display board details and also doesn't show any mods that were made to the pcb's (in my case a couple of caps were modded).

Not mentioned in the video, somebody asked about the TL494 function, as follows:
Looks like the TL494 ia acting as a pre-regulator. It's picking up the voltage "across" Q401 the main output FET (+ before, - after) and adjusting the duty cycle T202 in order to keep this to a minimal voltage......hence the small'ish heatsinks required considering it's a 60V/3A PSU. The voltage/current control is all done with the op-amps via the main Q401 FET. I've yet to confirm this by getting hands on again, but thats what it appears to be from the schematic.