Samsung UE32F4510 Red led blinking

[electrocuted]

I hear you, next time I will surely know where to start from...

[nomoresonys]

Yep, the one time I didn't give the solder joint speech early, that's why the simple things should not be overlooked. Would have been a shame to tear down to backlights and or buy a new powerboard, just for a bad solder joint that's fixed with a quick check and a little solder.

[electrocuted]

Thank you too, I just could not believe that it was something simple as that!

[vinceroger69]

Glad you managed to fix the tv in post 18 i mentioned might be a bad solder joints some are certainly hard too spot expecially when were diagnosing over pictures

[electrocuted]

This is the spot that was faulty!

[nomoresonys]

[electrocuted]

Well, congratulations to both of you, it was a cold soldering on the negative pin of CM851. I guess this was "informing" power supply that the led inverter was operational and it would not turn on. Thanks again for the help!

[electrocuted]

ok thanks, I'll look into that

[Davi.p]

So it's bad circuitry prior the mosfet, no you cannot make the short forever

[electrocuted]

Good news!!! the tv works with shorted DS on mosfet. I guess the noise is not harmful... what happens if I make the short permanent?

[Davi.p]

you did not well things, if backlight comes on on the last test then you have to check also main board psb outputs, if them ok then is highly difficult that jumpering A5v to power on did not turned outputs on.. THE QUESTION: have you ever tested a tv power supply?!

[nomoresonys]

Try to isolate the location of noise, maybe try a straw or rubber hose.

[nomoresonys]

Make sure all solder connections are good on bottom of board, search for bad solder joint images if needed.

[electrocuted]

Done, the backlight comes on with the cable to the main board disconnected! If it is connected nothing happens. A strange high pitch noise is heard from power supply...

[electrocuted]

I'll try that tonight because I have removed the power board from tv. If the led array is defective will it affect the inverter circuit?

[electrocuted]

N-Channel MOSFET - AOD4186

[Davi.p]

if ps-on is high, qm853 gate must be low, i guess is P channel, or not? before any other test you can jumper D-S of mosfet and plug everything, then plug tv to mains and see if it works..

[electrocuted]

I tried with ps_on to ground with same result. Seems it has no effect on the operation of the power supply, only a load on A5V "can" switch it on. I will recheck nearby items around QM853. ps_on unconnected measures 3.3V.

[Davi.p]

in Samsung led tv there is an internal pullup resistor that keeps high the ps-on with no main board, in your last photo the qm853, its gate connects to the bottom network, must check every resistor/diode/transistor for short/open, must also check ps-on V at unconnected PSB.

[electrocuted]

Sure, that's correct but how did the ps turn on without using the ps_on line?