Samsung UE40D5000 power board - 9.4V on B13V

[NoxiousPluK]

I'm strugling today with trying to fix a UE40D5000 power board.

A5V gives a nice 5V, B5V and B13V stay off until I short A5V to PS-ON, so far so good.

B5V comes up as a nice 5V as well but B13V gets me 9.4V max.

Also backlight doesn't get power, those pins stay at 0 even if I put 5V on BLU_ON (measuring across CH1+ and CH1- on CNL802).

After turning on PS-ON, I see about 165VAC going into TM801S; I'm not sure what voltage I should see there.

The caps next to CNL802 get 96VDC, which seems too low as well since CNL802 should be 268V. These caps are all in parallel.

I'm suspecting the input voltage to TM801S is too low, but I can't find what I should measure on the in- and outputs of this transformer.

Suggestions welcome, thanks a lot in advance!

Attached the circuit diagram for this specific board.

[lotas]

Re: Samsung UE40D5000 power board - 9.4V on B13V

When switching to operating mode, what is the voltage at the PFC output?
Should be around 400v DC.

[Davi.p]

Re: Samsung UE40D5000 power board - 9.4V on B13V

Try change ICM851 and PCM803, if doesn't work change ICM801, i guess you have correct 400vdc on PFC out. You cannot measure AC on TM801 because its a square wave
.

[dick_barton]

Re: Samsung UE40D5000 power board - 9.4V on B13V

What voltage do you have at each side of inductor L9801

[NoxiousPluK]

Re: Samsung UE40D5000 power board - 9.4V on B13V

When switching to operating mode, what is the voltage at the PFC output?
Should be around 400v DC.

I measured across CP803S because that should be the same voltage right? I get 320VDC both with and without PS-ON shorted to A5V.

Would that indicate something to be wrong on the hot side? I'm surprised the A5V is exactly 5V then tho.

Try change ICM851 and PCM803, if doesn't work change ICM801, i guess you have correct 400vdc on PFC out. You cannot measure AC on TM801 because its a square wave
.

I might not have the correct voltage on PFC out, see above!

What voltage do you have at each side of inductor L9801

I'm not sure where to probe for this; see attached images.

Thanks so much already

[lotas]

Re: Samsung UE40D5000 power board - 9.4V on B13V

Yes, your PFC does not work.
PFC is not related to STB 5v.
In the standby power supply, the PFC does not work and the output should be 320v, when switching to the operating mode, the PFC should give out about 400v.

[Davi.p]

Re: Samsung UE40D5000 power board - 9.4V on B13V

I tell you the following test, retest PFC out but right after test for the B13v, i suspect your ON command was not ok. 5V are stable because them are took from standby ps through a mosfet. If pfc again is low check M_Vcc, must be maybe something around 5-15v, if present replace ICP801

[lotas]

Re: Samsung UE40D5000 power board - 9.4V on B13V

What is the voltage across the CP811 capacitor?