Korad KD3005D Power Supply - Fan Problem

[CarsonReidDavis]

I had been using my Korad for a few weeks when I realized that the fan never seemed to run. I listened in the back and it was making a odd humming sound.

So I took the unit apart and fed the fan voltage directly from a power supply and it worked fine. Then I metered the board output to the fan and it gave a reasonable voltage that should run the fan.

Confused, I hooked the fan back up to the board and measured the voltage the board produced under load. This time the board failed to produce nearly enough voltage to power the fan and the fan made that same sad humming sound.

Here is an album with various pictures of the PCB and descriptions from my testing https://imgur.com/a/xNmjzks.

Any ideas what I should be looking for to fix?

[Mosaic]

The fan is run by a temperature triggered circuit. Probably from a thermistor feeding the wiring harness running to the front panel from where the fan gets its power.
Simplest solution is to tie the fan directly to a 12V power rail and let it run when the unit is on.

My Korad died after 15 minutes of first use while figuring out how the CC mode worked.
Blew the main fuse.
So I put in a larger fuse and heard the Transformer doing a loud buzz. Yet the front display came up.

Something was loading it severely, when I removed the heavy  4 pin high current connector to the rectifier board from the xformer the buzz went away.
So I let the buzz continue for about 30 sec and out popped the magic smoke near the bridge rectifier.

Tested the rectifier and the two NPN power bipolars and the rectifier had 2 shorted diodes. NPNs were fine.

Popped in a 35A aluminum block type bridge I had and wired it into place screwing it into the bottom of the Alum heatsink. Overkill , but I had that for years from a  electronic goldmine promo sale waiting for a purpose.

Unit is fixed and fine now.