TV Phillips 42PFL4307H/12 power supply with LED driver problem

[darkoan]

Hi everyone

I am trying to repair LED LCD Phillips 42PFL4307H/12 with PSU problem. I already replace suggested components U101 FSL106HR integrated high voltage PWM switch and U501 L6599 high voltage resonant converter and also Q581 STK0160 with no luck.
I measure output voltages and I have only two outputs:
3V3stdby = 3.3V
Standby = 2.6V
+12V = 0V
+Vsnd = 0V
I check voltage at main filter cap C646 and I only have steady 320V and not 380V ~ 400V as I expect from PFC stage.
Also Vcc voltage is missing and no Vcc to U601 SCY99102BDR2G PFC controller and both U101 and U501.
What is good to check or measure next to get Vcc voltage?

[CapLeaker]

Re: TV Phillips 42PFL4307H/12 power supply with LED driver problem

To get Vcc you have to force on the PSU first. The PFC isn't turned on in STBY mode. So if you put 3.3v to STBY through a 1k resistor, you should get Vcc. If you don't, check around Q101 and Q301. The STBY pin isn't a output. It is the STBY input, to tell the PSU a to fully turn on. THere will be no 12V or backlights until the PFC is working and you get like 380V DC on the main filter cap.

[dskall]

Re: TV Phillips 42PFL4307H/12 power supply with LED driver problem

Your PFC voltage is to low. I cannot see back of board good enough but on your U601 there is a feedback terminal there should be several smd resistors in series. You need to check resistance one or all to low.

[darkoan]

Re: TV Phillips 42PFL4307H/12 power supply with LED driver problem

Thanks for your replays.
I put 3.3V to STBY pin through a 1k resistor and nothing happened, no Vcc.
Can I measure some voltage on optocouplers PC101 and PC102 close to Q101 and Q301?
I only get +1.06V on diode side of PC101 optocoupler...

[budm]

Re: TV Phillips 42PFL4307H/12 power supply with LED driver problem

If you look at the schematic, switched Transistor Q301 is PNP, so for the rest of the power supply to turn on, you have to GND STBY pin, it is ACTIVE LOW circuit, the Base Voltage has to be lower than the Emitter for that PNP to be on.
You also need to test PFC diode D601/601A to make sure they are not shorted out or have low resistance reading.

[budm]

Re: TV Phillips 42PFL4307H/12 power supply with LED driver problem

BTW: your post 1:
'Standby = 2.6V' That should go low when TV is turned on.

[darkoan]

Re: TV Phillips 42PFL4307H/12 power supply with LED driver problem

Sorry guys to make such a confusion here budm was right... (Thanks budm for make this things clear now.)
I am able to turn power supply on with GND and STANDBY pins and get right value from PFC on the main filter cap around 325V to 390V.
And voltages on connector 1M95:
3V3stdby = 3.3V
Standby = 2.6V and go low (as expected)
+12V = 12.32V
Vsnd = 12.32V
BL-ON = 0V
BL-DIMM(Vsync) = 0V
BL-I-CTRL= 7.64V
POK = 0V

And on connector 1M11:
+12V_AL = 12.32V

Is this values good or can be somewhere different?
What else can I test next?

[budm]

Re: TV Phillips 42PFL4307H/12 power supply with LED driver problem

"BL-ON = 0V" The backlights ON signal does not change state at all, it stays LOW?
It should go high.

[darkoan]

Re: TV Phillips 42PFL4307H/12 power supply with LED driver problem

I put power supply unit back to TV and I hear high frequency noise on large transformer which seems to me like at normal operation.
+12V line is on for around 40 seconds than stops for 3 seconds and the cycle is repeating and it looks like enable some sort of protection circuit.
Now with PSU inside TV signal BL-I-CTRL is 3.6V and BL-ON is not changing just a couple of millivolts.

[budm]

Re: TV Phillips 42PFL4307H/12 power supply with LED driver problem

BL-ON, PS-ON (STBY), DIM are from main board.
Need to look at the POK signal to find out if it is low = normal or high = normal.

[darkoan]

Re: TV Phillips 42PFL4307H/12 power supply with LED driver problem

Sorry for a delay in the meantime I also found block diagram and step by step info to check PSU. (see attachments)
I follow these steps and everything seems fine to me but the problem remains...

[budm]

Re: TV Phillips 42PFL4307H/12 power supply with LED driver problem

Sorry for a delay in the meantime I also found block diagram and step by step info to check PSU. (see attachments)
I follow these steps and everything seems fine to me but the problem remains...

Pot 9: "BL-ON is not changing just a couple of millivolts." So how can it be fine when the BL-ON is in milliVolt instead of what you should have per your chart?

[darkoan]

Re: TV Phillips 42PFL4307H/12 power supply with LED driver problem

Sorry but I understand this chart obviously wrong to pull pin BL-ON to HIGH (3.3V) by myself to start-up power supply and get reference voltage 5.96V at pin 25 on LED driver (U401).
As I see these 4 inputs are from the main board and other outputs are from the power supply unit:
2 - Standby,
11 - BL-ON-OFF,
12 - BL-DIM(Vsync),
13 - BL-I-CTRL.

[darkoan]

Re: TV Phillips 42PFL4307H/12 power supply with LED driver problem

Sorry but I understand this chart obviously wrong to pull pin BL-ON to HIGH (3.3V) by myself to start-up power supply and get reference voltage 5.96V at pin 25 on LED driver (U401).
As I see these 4 inputs are from the main board and other outputs are from the power supply unit:
2 - Standby,
11 - BL-ON-OFF,
12 - BL-DIM(Vsync),
13 - BL-I-CTRL.

What I want to say in other words that I think the problem is very likely in the main board itself, because BL_ON has to become from here (specifically from standby controller PNX85500)...

[budm]

Re: TV Phillips 42PFL4307H/12 power supply with LED driver problem

I indicated that in post #10, it is a matter of trying to fix the main board which without the correct diagram then it will be very difficult so all you can do is to do really good visual inspection and may be check the Voltage regulator ICs, etc.