40" Philips 40pfl4706/f7 No Power

[samehms]

Hi all,

I have an LED TV that died suddenly. It lost power completely. I tried the Remote Control and the power switch, getting no LED light or any response. The service center diagnosed it as a bad mother board and wanted to charge me $350. I think I can do this job by myself and save some money, but I am not sure which board is defective. It might be the power board or the mother board i guess. Any help is greatly appreciated.

[tom66]

Re: 40" Philips 40pfl4706/f7 No Power

Do you have a digital camera to take pictures of the boards, and a digital multimeter to take measurements of various items?

[samehms]

Re: 40" Philips 40pfl4706/f7 No Power

Yes ... I have both... I know from previous post to measure STB5.3V, I measured it on standby, and I got 5.2 volt. but I don't have other than standby since the system is not turning on at all.

[tom66]

Re: 40" Philips 40pfl4706/f7 No Power

OK, there's a pin legend next to the connector going to the main board (the main board is the one with the video inputs on it.) Can you either get a picture of this legend or tell us what the labels are?

[samehms]

Re: 40" Philips 40pfl4706/f7 No Power

[tom66]

Re: 40" Philips 40pfl4706/f7 No Power

OK, check in standby voltage on P-ON pin, same as done with 5.3V.
Then press power button while checking it, does it change? Does it go to 2V or more?

[samehms]

Re: 40" Philips 40pfl4706/f7 No Power

I didn't get any voltage on standby or even when I pressed the power button.

[tom66]

Re: 40" Philips 40pfl4706/f7 No Power

OK, this indicates the diagnosis of the TV repair shop is correct. Main board (=motherboard) is bad.

To rule out the power board completely you can try jumpering the P-ON signal, you will need a resistor of value from 100 to 470 ohms. Do you have one, can you get one easily? Wire it between the 5.3V and P-ON, with the connector disconnected from the main board, 12V should then be made available on the P-ON12V pins.

[samehms]

Re: 40" Philips 40pfl4706/f7 No Power

I don't have a resistor handy, but I will give it a try and let me know. Should I order a main board now, or wait for this test?

[samehms]

Re: 40" Philips 40pfl4706/f7 No Power

" let you know " .. sorry for the typo..

[tom66]

Re: 40" Philips 40pfl4706/f7 No Power

Wait for the test just so we can rule out a power board fault.

[samehms]

Re: 40" Philips 40pfl4706/f7 No Power

Alright... Thank you very much,, I really appreciate your help. I will let you know once I get this test done.

[samehms]

Re: 40" Philips 40pfl4706/f7 No Power

I am still looking for a resistor 100-470 ohm. Should I buy it? Can I make one, or how can I find it? Thanks

[tom66]

Re: 40" Philips 40pfl4706/f7 No Power

You can buy one from RadioShack, Fry's, etc. Make sure to get a through hole one-quarter watt 5% type. Value in range of 100 to 470 ohms, for example 330 ohms, 270 ohms are also acceptable. Buy more than one, they are easy to lose.

[samehms]

Re: 40" Philips 40pfl4706/f7 No Power

I just got the resistors today. I did the test, I shorted P-ON with the 5.3V (Pin #3 and Pin# 6 starting from the red wire) with 300 ohm resistor. I unplugged the cable from the main board and plugged the power cable, but I got NO voltage on the 12 volt pins!!

[tom66]

Re: 40" Philips 40pfl4706/f7 No Power

OK, this is interesting, it might NOT be a main board fault.
Was that with the connector disconnected from the main board end?

[samehms]

Re: 40" Philips 40pfl4706/f7 No Power

Yes. it was disconnected. I used that cable end to connect the resistor and check the voltage. i still get 5.2 voltage at P-ON and 5.3V while connecting the resistor.

[tom66]

Re: 40" Philips 40pfl4706/f7 No Power

OK, do you want to try repairing the power supply (you will need component testing experience, good soldering skills) or just replace it?

It is quite possible both the main board and power board are bad, because the main board should still try to make P-ON go high. Could be a victim of power surge damage.

[samehms]

Re: 40" Philips 40pfl4706/f7 No Power

I checked online, there is boards for about $25. Do you think that I should take the risk and try to replace only the power board for now? I connect the TV to surge protector, I don't know how I got that. It was working perfect and suddenly turned into black screen.

[tom66]

Re: 40" Philips 40pfl4706/f7 No Power

You can replace just the power board for now, with no risk to it or other components.
Surge protectors do nearly nothing to prevent damage to equipment through HDMI ports or the antenna/cable connection, unfortunately.