Hi everyone
I have a problem with Longwei K3010D power supply. It shows permanent 0V and 0A and CC led is lit. No reaction to V and A knobs.
I have found similar topic, read it and tried to follow suggestions.
https://www.eevblog.com/forum/testgear/problem-power-supply-tech-star-k3010d/What i have checked:
- there is no short on output, the resistance is ~160Ohm (two 330Ohm RA, RB in parallel for discharging output cap)
- power mosfets and schottky are ok
- 12V supply is ok
- VR and AR pots are ok, they are correctly wired to the mainboard
- U4 supply voltage is ok, reference voltage is ok
- TL084 (LM324) seems to be ok, input voltages changes with V and A knobs
- there is no output on SG3525, permanent zero with repetitive glitches, therefore the is no switching on power mosfets
- U4 pin 1 is 0.6 to 2.5V sensitive to VR, pin 2 1.2 to 2.2V sensitive to VR, pin 9 is 0.7V,
And I have no more ideas what to check.
After switching on the fan starts spinning for a while (less than 1 sec). And then power supply is dead. One can hear the coil(s) sound and its frequency changing with current knob.
Thanks for any ideas
The mainboard is K305D revision from 2019 so it is a little bit different than the one from the schematic. I observed that U1-B seems to be unused and there is no Q8, Q9, Q10, W2. U4_2 connected to R44 and D4_C