How I repaired my Chinese 24V/15A Power supply.

Thought I'd share in case it helps anyone in future.
PLEASE DON'T MESS WITH POWER SUPPLY IF YOU DON'T KNOW WHAT YOU'RE DOING! 350Volts in there!

My Chinese 6040z died during a v bit carving. Gutted.
Quickly established that the 24v power supply was dead.

I opened it up and started checking things. Fuse had blown, indicating fault was in high voltage side. Long story short...

Bridge rectifier partially shorted out, taking a power transistor and fuse with it. I always replace PWM Controller when power transistors have blown, just to be sure.

The diode bridge, PWM and Transistors were all Chinese clones of already cheap parts. I replaced them with more trustworthy original parts. The PWM got a slight upgrade as well.

Attachment 23515


Diode Bridge: KBU808 (8A/800v), replaced with genuine KBU1010 (10A/1000V)

Power Transistors: clones replaced with genuine FJA13009TU

PWM: cloned KA7500B Replaced with genuine KA7500C. The newer C version is more accurate and stable and a direct drop in replacement.

Schottky Diode: This diode was okay, but I included it as it is a likely failure point. It's running close to the supposed spec and as it's a Chinese brand, it's on probation. I would have replaced it, but didn't have a suitable part handy.

Total cost of parts £4.(€6)

Anyway- it's running fine now. Steppers sound more even toned when parked and power supply actually runs a fair bit cooler now.

Hope it helps someone.

Replaced partsAttachment 23516

Thanks for talking the time to post the fixing procedure and the parts you use.