Samsung UE32F4510 Red led blinking

[Davi.p]

so this means the feedback circuit is normally connected only to 5v line and you can't load only the 12v..

I see two power mosfets (D4186)

this is wrong name, D stays for diode, i see 2 power diodes coming in to power enabling mosfet QM853 (smd) , check it if good and follow its path to the connector..

[electrocuted]

Put an 1A approx. load to the A5V and see if it drops.. if yes replace the shunt regulator 431 similar.. check also the 400v big cap..

Tried it and voltage stays solid 5.2V. The strange thing is when I put the load, the voltages B5V and B12V are there on the connector! (ps_on unconnected) In fact the more amperage on the A5V line, the more voltage on B12V.
A5V B12V

0.5A 7V
>1A 13V

[Davi.p]

Put an 1A approx. load to the A5V and see if it drops.. if yes replace the shunt regulator 431 similar.. check also the 400v big cap..

[electrocuted]

It's difficult without diagram but I see two power mosfets (D4186) to switch on B5V and B13V. The B13V output is used to turn on B5V but both fets gates are 0 Volts! Inputs on these read 5.2V and 24V(!). When I connect a 24V led bulb the voltage drops to 15.5 and the bulb lights pretty low. Then when grounding ps_on it goes even more dim! I will continue tracking...

[electrocuted]

As far as I see for the first two transistors it seems ok. To change the voltage on these, power on input needs connection to ground (0V) and not A5V.

This service manual might help.

This is quite similar but not the same model. I can't find the exact same diagram for the power supply. This is the closest one I got:

[vinceroger69]

This service manual might help.

[Davi.p]

check the voltage on every axial diode on secondary, there will be, i guess, 5,2v, 12v, 17v , then check the path of the power on signal, first a resistor, then probably a prefinal transistor, then those power mosfet smd solder side.. eventually remove old solder and put new..

[electrocuted]

https://www.youtube.com/watch?v=azUHkApvQUI
https://www.youtube.com/watch?v=S_ZHOHUzxwg

Thanks, I've seen the video but this is not my case! Diodes test ok and they have voltage on their cathode. Tried to turn on power supply with leds disconnected, same zero voltages accross connector.

[yokoono]

https://www.youtube.com/watch?v=azUHkApvQUI
https://www.youtube.com/watch?v=S_ZHOHUzxwg

[electrocuted]

No, I had the leds connected. Let me try again and see.

[vinceroger69]

Measuring the voltage on the 3 large diodes (left side of transformer) I get 5.2V and 17v. It seems that the power on "fails"! Could it be a protection cancelling the power on procedure?

failed leds might cause protection circuit too kick in (did you have leds disconected when you jumped the two pins to test psu)

[electrocuted]

Measuring the voltage on the 3 large diodes (left side of transformer) I get 5.2V and 17v. It seems that the power on "fails"! Could it be a protection cancelling the power on procedure?

[electrocuted]

BN44-00604F

[vinceroger69]

I have read a thread on this forum where budm metioned on these power supplies the transformer suffers from bad soldering so this may be worth having a look at/re solder

[Davi.p]

why you posted a partial photo of the p. board? Post at least a link to a good photo, and better also of the soldering side..

[electrocuted]

Thanks for the help, shorted pin 12 with 14 (A5V and power on) but all voltages on connector still 0 volts!

[nomoresonys]

It's a samsung ue, pretty sure these have pull-up resistors, so unplug cable from powerboard to mainboard, plug powercord in, if backlights do not come on and stay on, the problem is with powerboard or backlight circuit which includes leds and the connections.

[Davi.p]

to test the psb at bench >jumper A5v + Power on, then apply dummy loads and test voltages, another road is to get a fixed PC power supply and feed the tv with it, 12v & 5v, you will not see the bright image due to BL off but you can test a bit..sound, dark images..

[electrocuted]

Done, all voltages are 0 volts except pin 12 (5.2V) and pin 14 (3.3V)

[vinceroger69]

can you check all the voltages like in post 3 of this thread Samsung ue32f4570ss with power supply BN44-00604F - Badcaps
I am not sure what pins need to be linked to test this power supply get us those voltages first then hopefully a more experienced member will tell us how to test just the psu output voltages