Author Topic: LG TV: image = No. sound = Yes  (Read 989 times)

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Snuf3

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LG TV: image = No. sound = Yes
« on: November 08, 2021,02:50:48 »
Hi Everyone
I have an LG 43UK6300 TV
After 2.5 years of use, the image disappeared all of a sudden but I can hear the sound (even the sound that comes from my PC /HDMI)

I want and I will repair it myself. But I need a small piece of advice.
I baked the motherboard at 200 degrees in the oven for 10 minutes (Utube Video) and the only result: I feel dumb  :57:- it didn't help.
When I opened the TV I saw that the LED lamps are working. They emit light
My next step: buying a Multimeter for checking the LEDs
I never worked with one. Will you think that this one should do the work?

 https://www.amazon.fr/Multimètre-numérique-AstroAI-amplificateur-tension/dp/B01ISAMUA6?ref_=ast_sto_dp

 
*If anyone has a suggestion / another step that I should follow - I will be happy to hear
*Should I check also other components with the Multimeter?

:c017:
« Last Edit: November 08, 2021,09:58:54 by Snuf3 »

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LG TV: image = No. sound = Yes
« on: November 08, 2021,02:50:48 »

downunder

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Re: LG TV: image = No. sound = Yes
« Reply #1 on: November 08, 2021,03:40:51 »

A multimeter would be a good step but not for checking the LEDs since you state the the LEDs are alight and therefore working, but it would be helpful to check if you're getting 12Volt on both sides of the fuse on the T-con board. The fuse will be tiny and located close by to where the flexi from the main board connects to the T-con.                Bruce

Snuf3

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Re: LG TV: image = No. sound = Yes
« Reply #2 on: November 08, 2021,09:56:38 »
Thanks, I will check it. After searching the net I think my situation is better described as "backlight but no display". When I turn the TV, it change to a shade of gray which mean that there is backlight. I have a question.
Since I never used a Multimeter:
1. can you tell me if the one I provided as a link is good for my needs?
2. Can it be that Most of the lamps are ok but there is a few defectives lamps that cause this problem?
3. I tried to "light torch the screen" test. I didn't see an image

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Re: LG TV: image = No. sound = Yes
« Reply #2 on: November 08, 2021,09:56:38 »

downunder

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Re: LG TV: image = No. sound = Yes
« Reply #3 on: November 09, 2021,02:23:40 »

Meter is fine. Yesterday all I got on the link was images of dogs. A faintly lit screen means that the backlights are working but no data is being fed to the screen from along the bottom of the panel -hence the need to check the fuse on
the T-con board. Unlikely that the backlights are faulty - a few dead LEDs will usually shut the backlights down due to current sensing. The torch test proves that no picture data is getting to the screen, so a faulty T-con or a faulty display are the likely scenario.

Snuf3

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Re: LG TV: image = No. sound = Yes
« Reply #4 on: November 14, 2021,10:38:33 »
 :c017:
I will open the TV and I will try to to the max tests possible.
Is there are some other test you suggest me to preform?

If I run over the different components . Can you confirm that my assumptions are correct?
LED: not causing the problem since I have a faintly lit screen + torch test that show no images
Power supply: I have sound, the TV is on. work perfect
Mother Board: Can/ should I test it?
T-Con: the first thing to test...

Snuf3

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Re: LG TV: image = No. sound = Yes
« Reply #5 on: November 14, 2021,13:31:31 »
Hi again
I saw some videos out there about the T con , fuse and some tests... But My T con doesnt look like a T con and it seems like I have 2 of them.
I attched some photos. You can see that the T con has the width of all the screen and also that I have two of them
Is this the T con? I am not really sure
Thnx

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Re: LG TV: image = No. sound = Yes
« Reply #5 on: November 14, 2021,13:31:31 »

Snuf3

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Re: LG TV: image = No. sound = Yes
« Reply #6 on: November 14, 2021,14:38:46 »
Well I guess that what I called the mother board is the T con but I want to aboard another subject.
I saw a video of someone who manage to FIX the problem by taking a pen and painting over the cable and blocking pins
When I do it I see that the right cable presnet half white screen image (dim, not strong white)
and the left one show no image. So I  think that the cables may be the problem.
Here is the video. I find his solution orginal. I can't do it myself since he didn't explained it in English
https://www.youtube.com/watch?v=NVyX5r_nPi8

downunder

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Re: LG TV: image = No. sound = Yes
« Reply #7 on: November 15, 2021,02:49:08 »

I see what you mean re T-Con - must be incorporated into the main board -copying Samsung. The panel itself may well be the problem. A defect on one half can cause the entire screen to blank out. May do well to try the "block-off" method in the video. Not sure what the artistry  was about but he was actually using sticky tape to isolate (block off) some of the contacts on the flexi cable.

Maybe he was lucky, or found the defective line before he made the video, because I spent 3 days last week on a similar Samsung 65 inch trying to achieve a similar outcome. Eventually I had to scrap it. An additional problem with the Samsung is that if you remove either flexi, the TV will not start. Good luck - Bruce

Snuf3

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Re: LG TV: image = No. sound = Yes
« Reply #8 on: November 17, 2021,09:33:26 »
Thanks Bruce.
your answers help me and motivate me to not give up.
You said that a defect in one half can cause this problem and this is what I am going to check
Is there a way to isolate the source of the problem?
Can I do a test to see if it's the cable that is the source?
maybe to switch the right with the left?
My goal is to eliminate component by component till I find the problem.
(I am starting with the cable since it's the comp. that is less complex) .

Thnx
« Last Edit: November 17, 2021,09:35:39 by Snuf3 »

downunder

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Re: LG TV: image = No. sound = Yes
« Reply #9 on: November 18, 2021,03:26:00 »

Hi Snuf3. You can try removing one of the two flexi cables (LVDS cables) while the TV is OFF. Switch on and observe the screen. If the panel is OK you should get a clean white screen on half the panel (disconnected side). Then refit the flexi and disconnect the second one and power on again.
Report your results. This works on conventional LED TVs that have a separate T-Con but some TVs like the Samsung with no T-Con board cannot be tested this way because an SOS signal is generated via the LVDS cables to disable the TV.

Snuf3

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Re: LG TV: image = No. sound = Yes
« Reply #10 on: November 20, 2021,07:04:47 »
Hi Bruce
thanks for your test. I did it and you can see the results in the pictures: the cables config. and the result
I will describe it also:
when the red cable was connected and the white was disconnected = Nothing. Black Screen, sounds NotOk.
when only the white LVDSi s connected = > half panel is in white, sounds OK.
(The white in the picture is more strong the in reality).
Tell me what do you think. and something to wonder about - if this test teach us that the panel is NotOK. is it possible that the panel is OK and I'am dealing with a faulty cable?

Thanks
Adam
« Last Edit: November 20, 2021,07:07:00 by Snuf3 »

downunder

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Re: LG TV: image = No. sound = Yes
« Reply #11 on: November 21, 2021,02:10:03 »

You've done well with that test. So it looks like one half of the panel is dragging down the whole screen. Only thing left to do is to remove the covers on the two long strips along the bottom of the panel and check all the surface mount capacitors on the bad half for shorts. Both boards will have a fair similarity so you can do comparisons. If you come up blank with that, then almost certainly the panel is faulty.            Bruce

Snuf3

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Re: LG TV: image = No. sound = Yes
« Reply #12 on: November 23, 2021,10:20:05 »
Hello Bruce
Listen I have a vocabulary issue. It's the first time I open a TV (but I am doing quite well thnx to you)
I attached a picture with the way I call the components, can you indicate which of the components is the panel?
after I will understand which part I need to check -I will check it. I imagine the it's done with the multimeter. is it's so - should I test for voltage or for the test with the beep sound?
I have also attached a photo of my idea of capacitor :)

Thnx again

downunder

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Re: LG TV: image = No. sound = Yes
« Reply #13 on: November 24, 2021,02:52:36 »

OK, so where you've written "end point", after you remove the speakers and the wi-fi module, you'll find usually 2 metal strips. Remove these as well and underneath you'll find 2 thin long circuit boards attached to the display panel (= panel). This also is the entry point for the 2 large flexies which are removable here if necessary.

These 2 long boards feed data into the display panel and it's on these that you'll find the capacitors, not the type you've pictured but tiny chips (chips) which are surface mounted and designated C---. Usually quite a few on each board. While you are there, make sure no liquid has found its way down the screen front and caused corrosion at the many flexies that are bonded into the panel base. This is bad news for a display panel and can also cause "no image". See how you go with that.

Snuf3

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Re: LG TV: image = No. sound = Yes
« Reply #14 on: November 28, 2021,11:36:34 »
Hi Bruce
first of all - have a nice weekend.
I took off the speakers so I can have access to the long boards. 1 picture == 1000 words so...
Pic No 1. I just verify that we are on the same page and this is the part.
Pic 2. The black arrow is what I understood to be a capacitor (tiny chip with cxxx). 
the part I circled with purple color is something I checked for the "bip" test (it was ok)
the red arrow. should I check that? I see that at the end of each one there is a gold circle (is it for test?).
Pic 3. This is were I am puzzled  . I don't know what setting I should have in the multimeter (what to check?)  and if my checking method is correct (one side on the capacitor the other side on a metal board) and most important of all - what values to expect? how  to know if I am in the correct range...
Hope I was clear. If not - tell me and I will clear things if I can.
Thnx Bruce

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Re: LG TV: image = No. sound = Yes
« Reply #14 on: November 28, 2021,11:36:34 »

 

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