Fried DC PS QW-MS605D

[dxk3355]

I was using my power supply (QW-MS605D) for some electrolysis when the connection shorted out after I did an adjustment and the PS went dead. I opened the case and can't see anything like a blown cap or resistor, but the back end near the power plug smells like burned stuff. Every time I swap the fuse (250V F5AL) it pops the fuse the instant I turn it on so the smell could be lingering from the last fuse. There's an older thread on here from where someone else burned theirs's out but they had obvious issues, I can't really see anything that looks burned out on mine which makes this a bit annoying. The board layout is here too from that other thread but I don't think I'd be able to figure from that likely sources of the issue. Any help would be appreciated.

[harp]

Check with dmm all semiconductor for short, dont just replace fuse... marking on resistors also must be intouch, clear...

[dxk3355]

Thanks, I got out my DMM and got readings from every resistor and did a better visual check and they seem fine. I also checked the diodes and they appear to be functioning as well.

[harp]

The bridge rectifier, transistors and mosfet also has correct reading, no shorted? Then check electrolitic capacitor for short... there is some path that drow current a lot...

[прямо]

Diodes can be measured as ok with DMM but in reality they maybe not. I just repaired an ATX PSU a few days ago that had a Zener diode failure. It failed to clamp the dropped high DC voltage and gave me a random low voltage below the minimum voltage to start the PFC+PWM IC, but the diode itself is measured ok with DMM. Still is in fact. 0.7V voltage drop and OL the other way around. But it simply doesn't work. After I replaced it with a new Zener diode from my stash, the PSU is working again.

To stop the fuse from keep blowing up, use a dim bulb in series with the mains.

Like harp said, you should check the bridge rectifier and the main switching transistor/MOSFET.

99% of the time when they are shorted, they will keep blowing the fuse.