Faulty Samsung PSU (BN44-00427A)

[subserver]

Hi everyone, I am new here so please forgive me if I have not formatted this correctly


I had a samsung TV where by it keeps clicking on/off but there is image when it does so. I opened it up to check for bad caps but they all visually appear fine. So I found this thread related to checking the mosfets:
https://www.badcaps.net/forum/showthread.php?t=22919

While checking to see if the gates were letting voltage through I noticed that if I put my volt meter from ground to the middle pin of either of the mosfets in the image indicated, the TV operates fine.

As such, I pulled the mosfets out thinking they would need replacement, but they seem to test fine (charge/shorting the gate enabled/disables throughput for the drain.

I also noted that unlike in the thread above, I still have the same issue if I entirely remove my mosfets.

Any assistance making sense of what is going on here would be greatly appreciated!

[dick_barton]

Re: Faulty Samsung PSU (BN44-00427A)

Initially I would touch up all the solder joints in that area and see if that improves things.
Can you post a clearly focused picture of the underside of the power supply in that area.

[budm]

Re: Faulty Samsung PSU (BN44-00427A)

I the other thread the OP has one shorted out MOSFET for the PFC circuit, you can get the TV to work when you touch the probe with the Voltmeter, but what did you use for ground? It can also be due to bad solder joints as suggested.
I would at least check the Voltage between the two legs of the main filter cap to see if the PFC Boosted Voltage (380 ~ 400VDC) is present or not when TV is turned on or you can run the board by itself without having cable between the main board and the power supply board connected, then check and see if you have >2V at the PS-ON, if you do then the PFC Boosted Voltage should be present.