Panasonic LCD TV: TX-L42ETW5 won't display anything

[lmhtb]

Symptoms:
Power On = green power LED flashing until it stays green. Any remote input turns the LED flashing then turns off. Trying to reset the TV, got me a 13 red code. (TV bought in 2013, wasn't used for a few months, tried to turn it on after that period, won't produce sound or video.)

What did I try?:
Google lead me here to threads stating that my "A board" has to be replaced. (I assume that's where all the video inputs are.) Have looked on platforms like Ebay for replacements board, didn't find anything.

So I wonder if I could repair it myself with your help?

Here are some pictures of the boards:

https://imgur.com/a/fB42rBl

[nomoresonys]

Re: Panasonic LCD TV: TX-L42ETW5 won't display anything

If you have a multimeter, try test number 3 below, try to do it just as instructed.

[Davi.p]

Re: Panasonic LCD TV: TX-L42ETW5 won't display anything

Try do detach the tcon board that is the one on the bottom hided by a pair of shields, and then turn on tv with antenna in and scroling channels to find one with sound.

[lmhtb]

Re: Panasonic LCD TV: TX-L42ETW5 won't display anything

@Davi.p

I've tried that and there was nothing. But I don't think that you can find any tv channel that way here in Germany, tho. They have changed the public tv channels to DVB-T2 few years ago.

@nomoresonys

I will do so as soon as I have a multimeter here.

[Davi.p]

Re: Panasonic LCD TV: TX-L42ETW5 won't display anything

Don't mismatch words, i've said to plug the antenna not to switch to analogue...

[lmhtb]

Re: Panasonic LCD TV: TX-L42ETW5 won't display anything

So finally I got a multimeter.

Here are my readings starting from Pin 1 to P2 to 15:

Power On
Power Off


16.13V
7mV and decreasing


16.13V
4.9mV and decreasing


16.13V
4.4mV and decreasing


-0.37mV
-3.7mV


5.27V
5.27V


-0.37mV
-3.7mV


2.49V
2.49V


3.3V
3.3V


3.3V
3.3V


67mV
67mV


0.08mV
0.8mV


~40-70mV
~40-70mV


5.2mV
5.2mV


~40-70mV
~40-70mV


0.00mV
-3.7mV

[dick_barton]

Re: Panasonic LCD TV: TX-L42ETW5 won't display anything

I found some information on your power supply (page 35) which may be of some use.
Check for 24V on P4 pins 7,8 and 9

[lmhtb]

Re: Panasonic LCD TV: TX-L42ETW5 won't display anything

OK I've checked P4 (1-12):

Power On
Power Off

5.1mV
0mV

0.8mV
0mV

67mV
3.28V

-4,3mV
0mV

-4.4mV
0mV

-4.3mV
0mV

24.7V
15mV and decreasing

24.7V
12mV and decreasing

24.7V
10mV and decreasing

3.3V
3.3V

3.3V
3.3V

-4.6mV
0mV

[dick_barton]

Re: Panasonic LCD TV: TX-L42ETW5 won't display anything

You have no BL_On signal (P4 pin 2 = backlight on signal) so you need to trace it.


Edit
It looks like it may well come from IC8000 which is an MN2W50250B, a large BGA device.

[lmhtb]

Re: Panasonic LCD TV: TX-L42ETW5 won't display anything

so if it is the ic8000, can I try to reflow it?

[dick_barton]

Re: Panasonic LCD TV: TX-L42ETW5 won't display anything

I would wait and see what others say but in the meantime you could do a search on BGA reflowing on the forum.

The manual I posted is not for your set but used the same power supply. Can you find the service manual for your set to confirm how BL_ON is controlled. It may be done differently on your set.

But what you have tested does show that the BL_ON is not being switched on.

[lmhtb]

Re: Panasonic LCD TV: TX-L42ETW5 won't display anything

I have found one on this site: http://televid-sib.ru/index.php?topi...7497#msg127497

[dick_barton]

Re: Panasonic LCD TV: TX-L42ETW5 won't display anything

That's the power supply board only and shows BL_ON link between P2 and P4 so not of any help.

Can you find the mainboard schematic TNPH0993 (TXN/A10WNUE). Can't see the number clearly.

[lmhtb]

Re: Panasonic LCD TV: TX-L42ETW5 won't display anything

I've found something here: https://****************/forum/86-85408-1
I am trying to register there and I am waiting for an email confirmation code, right now.

I've also tried heating up the ic8000 with a hairdryer for 10 minutes now, but nothing changed. I assume there was not enough heat. On this thread (same symptoms my TV has) one guy has been baking his whole A board which I could try too: https://www.badcaps.net/forum/showthread.php?t=22926

[Davi.p]

Re: Panasonic LCD TV: TX-L42ETW5 won't display anything

But the backlight is working? If yes try to change tcon, or if you can wait me to be back on the board i show you some tests to be made on tcon..

[lmhtb]

Re: Panasonic LCD TV: TX-L42ETW5 won't display anything

no, the backlight is not working. Anything I can test on the tcon board first?

Btw, I have failed the test on that stupid website, it's hard to answer 5 of 6 questions right when using google translator... Without passing that test I can't get the file. Had 2 tries my best was 4 of 6.......... At least, I can try it again the next day...

[nomoresonys]

Re: Panasonic LCD TV: TX-L42ETW5 won't display anything

IS there a map/legend of the P2 connector pins on the underside of the powerboard?

[diif]

Re: Panasonic LCD TV: TX-L42ETW5 won't display anything

no, the backlight is not working. Anything I can test on the tcon board first?

Btw, I have failed the test on that stupid website, it's hard to answer 5 of 6 questions right when using google translator... Without passing that test I can't get the file. Had 2 tries my best was 4 of 6.......... At least, I can try it again the next day...

There isn't anything useful in the zip file, just a slightly blurry photo of the mainboard without the big heatsink.

[lmhtb]

Re: Panasonic LCD TV: TX-L42ETW5 won't display anything

@nomoresonys

There is a screw I can't screw off... I've tried for 10 minutes (with pliers/drilling machine using different drilling bits and rubber). I will have to bruteforce it later...

@diif

thank you

[nomoresonys]

Re: Panasonic LCD TV: TX-L42ETW5 won't display anything

Oh shit, lol, be careful not to damage it.