It might be worth checking ZD2 and U2, this is an Overvoltage protection zener and opto-coupler, to prove it faulty lift out one leg of the zener, and see if it stops ticking.

Its still ticking...
I think I should drop this repair project now. Invested too much time with no success till but learned too many lessons.

 

Its never a waste of time when your learning and nothing to feel bad about scrapping it now.

 

How likely is it that the transformer will fail?

 

How likely is it that the transformer will fail?

Most unlikely. It is probably the most reliable component on the board.

 

This is why i give myself an hour to fix an smpsu, then it becomes Uneconomical, better to bin it now than getting sucked in with it..

Don't feel let down because you can't fix it, some you win some you loose...

God loves a tryer...

 

I reverse engineered the board.

 

I wasn't knowing the how the transformer was wound and multimeter didn't helped either because of too low resistances. So i drew it as it is numbering the pins.

 

The tag X1 is on pin1 of U1 and not after R14, although R14 is a zero ohm resistor it won't matter much anyways.

 

Now I am wondering if this supply is like a computer supply in needing some minimum load. An automotive headlamp with one section burned out, or a couple of them, should be a load of half the rating and ought to be good enough. That may or not give a clue and it should be easy to try. Another thing to do is to monitor the voltage across that filter capacitor after the bridge, which I am guessing is the big one on the board. If that voltage varies in time with the clicking let us know.

 

Now I am wondering if this supply is like a computer supply in needing some minimum load. An automotive headlamp with one section burned out, or a couple of them, should be a load of half the rating and ought to be good enough. That may or not give a clue and it should be easy to try.

Actually i have tried by connecting simple dc bulb to it... The 7.21 volts that is on output it drops to zero after loading. So i thought there must be something wrong with the feedback so i replaced tl431 after that alteration this ticking thing happened.

 

Another thing to do is to monitor the voltage across that filter capacitor after the bridge, which I am guessing is the big one on the board. If that voltage varies in time with the clicking let us know.

Around 150 volts on each caps and its going up n down 2 volts.

 

Looks a strange set up on pins 2, 3,. The TL431 opto usually goes to pin 2 Vfb directly no Q2??, and over voltage goes to the same pin, R11 from the output doesn't look right going to pin3 Cfb (Current) you may have drawn it wrong..

Good attempt well done for re-engineering, as a try remove the output Collectors of the opto-couplers, and see if it stops ticking and you should get maximum voltage output, then put back the TL431 opto, see what happens?

 

Good attempt well done for re-engineering, as a try remove the output Collectors of the opto-couplers, and see if it stops ticking and you should get maximum voltage output, then put back the TL431 opto, see what happens?

Then the output voltage may get very high, especially with no load, and convert the output capacitors into mortars - ka-boom.

 

I thought the same thing... If there wouldn't be any feedback then there is nothing to limit the duty cycle and the output will go as high as it can and may eventually burn things up.

 

may eventually burn things up.

And 'eventually' may be a short period of time.

 

What is the model number of this power supply?

 

What is the model number of this power supply?

YL338 03

 

I thought you said that was the number on the PCB? I'm asking what the actual power supply make and model are?

 

I thought you said that was the number on the PCB? I'm asking what the actual power supply make and model are?

 

https://m.aliexpress.com/item/32818...y8O6Wke-fzAE4DK8o0PTsdiZ6GWddLF31561046070653

What you guys think of this power supply... Its on sale... Should I buy?