Philips 47" LCD TV.. Dead..Model # 47PFL3704D/F7

[MisterD]

This TV was given to me and the guy said it went out during a thunderstorm, so I'm assuming lightning or power surge. He said he replaced the power supply board himself and that didn't fix it so he didn't want to mess with it. I have checked dc output voltages on the power supply in marked locations on pin connectors, has 3.3v standby and 12v present. I could not find anything marked PSON anywhere, it does have a small multi-wire connector going from the IR Board to the main board and the 3.3v is present there as well. I didn't see any small fuses on the Mainboard, at this point I think the problem is on the Mainboard, not sure if the board can be diagnosed and repaired or if I may end up having to buy a replacement board. I would appreciate any help and guidance I can get. I attached some pictures. Thanks in advance

[budm]

Re: Philips 47" LCD TV.. Dead..Model # 47PFL3704D/F7

Philips will sometime use 'STBY' instead of PS_ON.
Can you take close up pictures of the two white connectors on the top right of the power board? You may be correct that the Main board is damaged. Try disconnecting the T-CON board connector to see if the TV will start.
The surge may have come through the antenna connector which can easily wipe out the main board and T-CON board.

[MisterD]

Re: Philips 47" LCD TV.. Dead..Model # 47PFL3704D/F7

Disconnected T-CON board, TV still not powering on. here are the close up pictures of Power Bd. Connectors.

[MisterD]

Re: Philips 47" LCD TV.. Dead..Model # 47PFL3704D/F7

I don't know if Philips uses a Standby Light in the front like Vizio, but anyway I did not see any light at all.

[budm]

Re: Philips 47" LCD TV.. Dead..Model # 47PFL3704D/F7

OK, the STBY is the PS_ON pin, you should see it goes or goes down when you hit the power switch since Philips may use reverse logic for turning on the power supply.
Most TV will use anything more than 3VDC = ON, Philips some time will use > 3VDC as off and 0V for ON. But no matter what you should see the voltage at this pin changes when you turn the TV ON/OFF.
What is the chassis number of this TV Model?

[MisterD]

Re: Philips 47" LCD TV.. Dead..Model # 47PFL3704D/F7

Okay, on the connector in the left picture above, at the bottom 1st pin is labeled 3V3 STBY and the 2nd pin is just labeled STBY, the 3V3 STBY has 3.3 volts no matter what, hitting the power switch or using the remote power does nothing, no change in voltage. The other pin 2nd pin up labeled STBY does Not have any voltage at all, power switch does not affect it.

DID NOT SEE CHASSIS # but SERIAL # starts with YA2B100

[MisterD]

Re: Philips 47" LCD TV.. Dead..Model # 47PFL3704D/F7

Does anyone know what this is? it is very small and also almost looks clear on top with a round yellow ball or dot inside. It is located on the Mainboard of this Philips TV, it checks open both directions on 400 ohm scale.

[MisterD]

Re: Philips 47" LCD TV.. Dead..Model # 47PFL3704D/F7

I removed and inspected the Main board, didn't see any fuses or anything obvious,this looks like another one where I will have to purchase a new/used Main board as a process of elimination, not getting much help, Since the Power Supply board was already replaced I assume it is good...looks like I'll have to remove the complete chassis from where it mounts just to get to the TCON board if it's bad. Any advise would be greatly appreciated.

[budm]

Re: Philips 47" LCD TV.. Dead..Model # 47PFL3704D/F7

" the 3V3 STBY has 3.3 volts no matter what, hitting the power switch or using the remote power does nothing, no change in voltage." 3.3V standby is OK, but the main board is not sending out any turn on signal. So main board is bad some where.
What you can do to see if the backlights inverter is working or not, you can remove that connector (3.3v, stby) from the power supply board and use 1k resistor to jump between the 3.3V pin and the STBY pin next to it, and another 1k resistor between 3.3v and the BL_ON pin on the other connector, the backlights then should come on, that way you will not get a surprise that you also have bad backlights.

[MisterD]

Re: Philips 47" LCD TV.. Dead..Model # 47PFL3704D/F7

Didn't have any 1k resistors to try, you are saying to disconnect the connector on the main board side so it leaves a way to slide the resistor leads into the connectors on the power supply and to jump as you have indicated, I tried that with some 500 ohm resistors when jumping the 3.3V pin and the STBY pin next to it, I still had the 3.3v but when I used another 500 ohm resistor between 3.3v and the BL_ON pin on the other connector the 3.3 dropped to 1.8 and no backlights, I did notice when I had the connector from ps to main bd. unplugged that the other STBY pin next to the 3.3v pin had 2.5 v but would drop to zero volts when the connector was back on the main board.

does that mean when applying approx 3.3 volts the BL_ON on pin on the power supply bd. that it should make the backlights come on by switching on the 24 volts to them?

[budm]

Re: Philips 47" LCD TV.. Dead..Model # 47PFL3704D/F7

It drops to zero because the switching transistor on the main board is stuck low, that is why you have to remove the cables (2) between the main and the power supply. I am surprised that the 3.3V standby drops down to 1.8V with 1k and 500 ohms load. That 3.3V power supply should be able to drive slightly less than 500 Ohms load with no problem and stay at 3.3V

[MisterD]

Re: Philips 47" LCD TV.. Dead..Model # 47PFL3704D/F7

Is it possible to just jump the 3V3 standby that has the 3.3 volts present to the other pin next to it on the same connector that is labeled standby to see what will happen. in other words is there a way to force the tv to power on or start up the power supply, but not knowing if there are any shorted components on the main or TCON Board?

[tom66]

Re: Philips 47" LCD TV.. Dead..Model # 47PFL3704D/F7

Usually it won't work because the microcontroller is stuck in some other mode waiting for some other condition, and this isn't being satisfied. Can be worth a shot though, sometimes it can kick other things into action...

[MisterD]

Re: Philips 47" LCD TV.. Dead..Model # 47PFL3704D/F7

I'm not where I can get to the TV right now, will be tomorrow sometime, I just want to isolate the problem, I can see a black mark on the chassis after removing the PS Board, the guy I got the tv from replaced the ps board himself after a thunderstorm, I'm wondering if the main board was damaged also. trying to figure out if I should go ahead and order a mainboard and get it on the way.

[budm]

Re: Philips 47" LCD TV.. Dead..Model # 47PFL3704D/F7

"The other pin 2nd pin up labeled STBY does Not have any voltage at all, power switch does not affect it." The main board is not working for sure.

[MisterD]

Re: Philips 47" LCD TV.. Dead..Model # 47PFL3704D/F7

I did notice when I had the connector from ps to main bd. unplugged that the other STBY pin next to the 3.3v pin had 2.5 v but would drop to zero volts when the connector was back on the main board.
Is that STBY voltage next to the 3.3v supplied from the main board or supplied from the power supply, or does it come from the power supply then go to the main board and then in turn the main board turns it on via the power switch?

[budm]

Re: Philips 47" LCD TV.. Dead..Model # 47PFL3704D/F7

The pull up resistor can be on the power supply board or on the main board, the signal will be kept at 0V when TV is in standby mode, transistor is on, when TV is turn on, the processor will turn the transistor off which will make the Collector pin of the transistor to go up toward the VCC which will turn on the power supply. That is why I ask you to put the 1K between the 3.3v and the STBY pin, this will turn on the 12v POWER SUPPLY section. So, do you get 12v output when the resistor is installed, disregard the other resistor for now.

[MisterD]

Re: Philips 47" LCD TV.. Dead..Model # 47PFL3704D/F7

I get 12.3 volts at the power supply anyway without installing a resistor on 3 pins of one connector and 2 pins on the other connectors shown on post # 3.

Also If I remember correctly while measuring some voltages on the power supply board I got either 18 or 24v on the cathode of the 2nd black diode marked 31DG going left to right from the word cold at the top of the PS Board.

[budm]

Re: Philips 47" LCD TV.. Dead..Model # 47PFL3704D/F7

Hmm, it sounds like this TV has 3.3V and 12v standby power supply.
So do you have the chassis number of this TV? I need to look for service manual for it.

[MisterD]

Re: Philips 47" LCD TV.. Dead..Model # 47PFL3704D/F7

DID NOT SEE CHASSIS # but SERIAL # starts with YA2B100