Riden RD6006 strange failure

[bogdan2014]

My Riden RD6006 power supply has failed in a weird way. I was powering a circuit and something shorted out on the PCB, then the PSU died. Upon inspection, there's no blown fuse, the switching transistor and diode are fine, but the auxiliary rail is shorted out. I removed most of the ICs but it's still there. Also checked the bigger diodes. There's no blown components, no burn marks, nothing really apparent.



I guess I'll have to start checking the smaller components...

[DavidAlfa]

Connect another power supply to the aux power, setting the nominal voltage, and start increasing the current.
At some point the shorted part will start to heat up. Ceramic capacitors like to do that sometimes.

But, just in case, take quality pictures where every part can be read. If the damaged part blows up, and the number is no longer readable, it'll be much harder!

[fixy88]

.... Ceramic capacitors like to do that sometimes....

Shorted MLCCs seem to be the new leaky electrolytic.... Super common fault.

[perieanuo]

i doubt it's a shorted cap, after how the short was caused, but the method of injecting dc with current limited and increased (i was lazy and i applied the nominal DC voltage on the rail with minimum 8 amps capability, the shorted component was quickly hot or even smoked)
i had a feeling not to buy riden seems i was right, they don't support those type of dut that shorts suddenly
maybe the schematic i attached seems close to yours

[edit] they say R22 should be replaced with something between 68K-100K if not already done, maybe you already know this
i added also the pdf's it's easier to follow the short

[bogdan2014]

I think I found the culprit, this small regulator heats up. There's no short at its output, so I guess it failed. On my board it's marked B6289P, but it has the same pinout as the one in the schematic.

[perieanuo]

so you have those 8.4V on output (my schematics and yours point that same voltage)?
https://www.olimex.com/Products/Breadboarding/BB-PWR-3608/resources/MT3608.pdf

[bogdan2014]

Haven't actually measured since even with a few volts at its input the current shoots up and the IC heats up. I assume that with the full 12V it will blow up and I don't want that. But I applied 8V at its output and there's no short.

[perieanuo]

just disconnect that ic input from the 5V rail and apply 5V from another power supply, you'll got either 8.4V either some burnt mt3608
i suppose you verified D1, C13, but my bet is mt3608 kicked the bucket  https://www.sigmanortec.ro/Modul-ridicator-tensiune-MT3608-5-28V-2A-p158720114

[perieanuo]

Haven't actually measured since even with a few volts at its input the current shoots up and the IC heats up. I assume that with the full 12V it will blow up and I don't want that. But I applied 8V at its output and there's no short.

actually, it's the other way: smaller the input voltage, higher the dissipated power, so power him with 5.3V like in the schematics, this will reduce power dissipation if the ic works correctly, dissipated power is (output voltage-input voltage)*current, i suppose current drawn is determined by your load and that load is not shorted. you need to verify if load on 8.4v rail is ok