Panasonic TC-L47E5 LED TV blinking red power light PLEASE HELP

[sfernandes]

Re: Panasonic TC-L47E5 LED TV blinking red power light PLEASE HELP

Ok I measured the pin 13 on connector A02 on the A board which is supposed to be the SUB-ON and it measures 2.475 at power on then when the fault occurs it drops to 0. Any idea anyone? Tom please give me a hand if your around.

[tom66]

Re: Panasonic TC-L47E5 LED TV blinking red power light PLEASE HELP

When SUB ON is high (>2V) do you have 24V?
Others around here can help too. Not just me.

[sfernandes]

Re: Panasonic TC-L47E5 LED TV blinking red power light PLEASE HELP

When SUB ON is high (>2V) do you have 24V?
Others around here can help too. Not just me.

I get positive 2v. no when sub on is high I get 0.038 not 24v. I have already replaced the ps with same result. I know others can help, but not much people helping me with this one.

[tom66]

Re: Panasonic TC-L47E5 LED TV blinking red power light PLEASE HELP

So, to recap:
Sub ON low: 24V measures LOW
Sub ON high: 24V still measures LOW

LOW: significantly smaller than rating.

Right? If so isolate the LED driver to make sure it's not shorted. But I think you do have a P board fault.

I'm going to say you probably got a dud board. Did you get the part off eBay?

Probably it is repairable if you're prepared to make some measurements and tests.

[sfernandes]

Re: Panasonic TC-L47E5 LED TV blinking red power light PLEASE HELP

So, to recap:
Sub ON low: 24V measures LOW
Sub ON high: 24V still measures LOW

LOW: significantly smaller than rating.

Right? If so isolate the LED driver to make sure it's not shorted. But I think you do have a P board fault.

I'm going to say you probably got a dud board. Did you get the part off eBay?

Probably it is repairable if you're prepared to make some measurements and tests.

correct, I have already replaced the led driver as well and same problem I got the board from a place called payless components it is a used board, but it is supposed to be tested and working. what kind of tests can I do on the ps?

[tom66]

Re: Panasonic TC-L47E5 LED TV blinking red power light PLEASE HELP

Ha, tested and working. Big lie, they don't test them. But anyway, ignoring that... Let's check a few more things.

Do you have 5VS? 5V standby. Pin 5 of P2, power board.

Do you have 16V? Check before & after SUB-ON goes high. Pin 1 of P2, power board.

Can you access the leads of capacitor C7422 on power board? Check voltage ACROSS that. Expect ~12V standby/24V after SUB-ON high.

Can you access the leads of capacitor C7514 on power board? Check voltage ACROSS that. Expect ~6V standby/12V after SUB-ON high.

This power board appears to drop the supply voltages in standby to save power. Everything runs at about half nominal rating in standby.

[sfernandes]

Re: Panasonic TC-L47E5 LED TV blinking red power light PLEASE HELP

Ha, tested and working. Big lie, they don't test them. But anyway, ignoring that... Let's check a few more things.

Do you have 5VS? 5V standby. Pin 5 of P2, power board.

Do you have 16V? Check before & after SUB-ON goes high. Pin 1 of P2, power board.

Can you access the leads of capacitor C7422 on power board? Check voltage ACROSS that. Expect ~12V standby/24V after SUB-ON high.

Can you access the leads of capacitor C7514 on power board? Check voltage ACROSS that. Expect ~6V standby/12V after SUB-ON high.

This power board appears to drop the supply voltages in standby to save power. Everything runs at about half nominal rating in standby.

Yes I have 5v standby

Yes I get 16v when sub is on high I get both the 2v on sub and the 16v at the same time then when sub goes down so does the 16v.

C7422 I get 26v, the cap is at 26v no matter if sub-on is high or low its always 26v

c7514 is good get 6v standby and 12v after sub on

[tom66]

Re: Panasonic TC-L47E5 LED TV blinking red power light PLEASE HELP

Great. Next step, the fault is around Q7402 then.

You will need to remove the board to get to the surface mount side and do some resistance/diode checks there with your meter. Please locate Q7402 on the bottom surface mount side (green side) and get a picture of that area so we can see the components around it.

In particular we need to see the ref-des (reference designator: Q7402, R832 etc.) of the components where possible.

Different design to what I expected. Appears to use the transformer differently depending on the output power. In standby like a flyback of sorts, when running like an LLC (resonant inductor-tank circuit.) Clever stuff. Cheap to make & low power in standby.

[sfernandes]

Re: Panasonic TC-L47E5 LED TV blinking red power light PLEASE HELP

Great. Next step, the fault is around Q7402 then.

You will need to remove the board to get to the surface mount side and do some resistance/diode checks there with your meter. Please locate Q7402 on the bottom surface mount side (green side) and get a picture of that area so we can see the components around it.

In particular we need to see the ref-des (reference designator: Q7402, R832 etc.) of the components where possible.

Ok ill get a picture for you in a few min. Don't know if this is related, but the ps has a silver like box that makes a click sound as the voltages drop. its a very low volume sound. Also don't know if this set has relays that click when you turn it on. because I don't get any relay clicks at all.

[sfernandes]

Re: Panasonic TC-L47E5 LED TV blinking red power light PLEASE HELP

Great. Next step, the fault is around Q7402 then.

You will need to remove the board to get to the surface mount side and do some resistance/diode checks there with your meter. Please locate Q7402 on the bottom surface mount side (green side) and get a picture of that area so we can see the components around it.

In particular we need to see the ref-des (reference designator: Q7402, R832 etc.) of the components where possible.

Different design to what I expected. Appears to use the transformer differently depending on the output power. In standby like a flyback of sorts, when running like an LLC (resonant inductor-tank circuit.) Clever stuff. Cheap to make & low power in standby.

Here is a picture of the area.

[tom66]

Re: Panasonic TC-L47E5 LED TV blinking red power light PLEASE HELP

OK pin 1 of Q7402 is marked with a yellow triangle.

Pins are then counted counterclockwise as so:
1 ... 8
2 ... 7
3 ... 6
4 ... 5

Test resistance (2000 ohm range) from 1 to 4 and from 5 to 4. I'm expecting to see infinite (your meter reading should not change, except perhaps very briefly.)

Then check what appears to be fuse PA7401. It should appear shorted (<3 ohms) on the same range.

[sfernandes]

Re: Panasonic TC-L47E5 LED TV blinking red power light PLEASE HELP

OK pin 1 of Q7402 is marked with a yellow triangle.

Pins are then counted counterclockwise as so:
1 ... 8
2 ... 7
3 ... 6
4 ... 5

Test resistance (2000 ohm range) from 1 to 4 and from 5 to 4. I'm expecting to see infinite (your meter reading should not change, except perhaps very briefly.)

Then check what appears to be fuse PA7401. It should appear shorted (<3 ohms) on the same range.

The fuse tests -2.800 and just keeps dropping. I have my meter on auto range. On the Q7402 how do I test that do I use both leads on my meter? if so where does the negative go and where does the positive go?

[sfernandes]

Re: Panasonic TC-L47E5 LED TV blinking red power light PLEASE HELP

The fuse tests -2.800 and just keeps dropping. I have my meter on auto range. On the Q7402 how do I test that do I use both leads on my meter? if so where does the negative go and where does the positive go?

Never mind I think I figured it out all the tests of the q7402 were infinity they didn't change they were all 0.2 ohms except for pin 4 which was 45.5 ohms but always stayed there and didn't move.

[tom66]

Re: Panasonic TC-L47E5 LED TV blinking red power light PLEASE HELP

For now, you can do it either way. The power board is disconnected while you make these checks right? Did not realise you have autorange meter. If so, please set it to continuity mode, which beeps when probes are shorted.

[tom66]

Re: Panasonic TC-L47E5 LED TV blinking red power light PLEASE HELP

Never mind I think I figured it out all the tests of the q7402 were infinity they didn't change they were all 0.2 ohms except for pin 4 which was 45.5 ohms but always stayed there and didn't move.

Huh?
Please check resistance between these two combinations 1-4, and 4-5. No more for now please.

[sfernandes]

Re: Panasonic TC-L47E5 LED TV blinking red power light PLEASE HELP

Huh?
Please check resistance between these two combinations 1-4, and 4-5. No more for now please.

I get 0.3 ohms. and if I put it on the continuity function it beeps. I hope im doing this right cause im not to sure.

[sfernandes]

Re: Panasonic TC-L47E5 LED TV blinking red power light PLEASE HELP

I'm confused about the numbering of the pins

I know pin 1 has the triangle, then not sure if pin 2 is below it or to the right of it

[tom66]

Re: Panasonic TC-L47E5 LED TV blinking red power light PLEASE HELP

My diagram is accurate for the orientation shown

>1 ... 8
<2 ... 7
<3 ... 6
<4 ... 5

[sfernandes]

Re: Panasonic TC-L47E5 LED TV blinking red power light PLEASE HELP

My diagram is accurate for the orientation shown

>1 ... 8
<2 ... 7
<3 ... 6
<4 ... 5

Ok but when you say test pins 1-4 do you mean one probe on pin one and the other on pin 4?

[tom66]

Re: Panasonic TC-L47E5 LED TV blinking red power light PLEASE HELP

I mean one probe on 1 and one probe on 4.
If you get continuity between 1 and 4, the MOSFET Q7402 is failed.