Mulja tv repair portal
Equipment Repairs => LCD TV forum => Topic started by: Snuf3 on November 08, 2021,02:50:48
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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
(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:
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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
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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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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.
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: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...
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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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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 (https://www.youtube.com/watch?v=NVyX5r_nPi8)
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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
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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
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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.
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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
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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
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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
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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.
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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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Those are the boards. The circled part is just a piece of fancy foam to prevent the board touching the metal strip. There are quite a few capacitors on each board, each soldered to the board at both ends. .These are the cap. terminals across which you need to measure. The gold spots are likely test points but I have no idea what they're used for. I see you have a digital meter so use ohms or the beep function. A reading below 100 ohms is suspect. If you find any, reverse the meter probes and recheck. It may read OK the other way. You'll likely find a matching cap on the other boards so you may compare reading. A totally shorted one would be a bonus as it will probably be your offender.
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Hi Bruce
How are you?
I checked the capacitors and they seems fine.
I took a bit of alcohol and I washed off the blue marker that was on the red cable(It came like that from the factory). It had an impact. By doing so and by blocking some stripes with a tape, the red cable show strong white input {{see image attached}}.
stronger than the white cable which give a weak and fade signal. By connecting the red and the white cables I managed to see a bright full screen.
Another thing that I think may help. There is a buzz sound from the motherboard. It continue also after turning off the TV. it dies only by taking the power cable out of the socket.
I feel like advancing. I finally got the red cable to show life signals and I found out about the noise.
it comes exactly behind the metal bar the I guess hide the integrated t-con.
Do you have a guess?
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Are you saying the buzz is coming from the Main board (the one with all the AV inputs on it)? And have you noticed the buzz before? I can only suggest that perhaps by blocking some stripes it has somehow upset the T-con on the main board. Is the buzz affected by finger pressure?
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Yes the buzz is coming from the main board. I haven't noticed the buzz before but it may be due to the fact that I didn't listened to noises . I think that I tried to press the metal cover of the T con and nothing happened. I would love to uncover that T con but the it's a bit tricky. there are 2 plastic screws with a Spring mechanism well I have a tendency to break things when I don't understand how they work so maybe I will save it for later
there is also a strange behavior: when I turn on the tv I see:
first I see only the left side which is really dim.
After 20 second a stripe appear on the right side
then the left side become bright almost perfect white!
and after that the right side become bright but more gray in color
there is a timing notion. I imagine it because of the blocked stripes on the cable
this is a 10 seconds video I made that describe 1 min of reality
I speed it up so it won't be boring to watch
https://youtu.be/6OuithZyBNg (https://youtu.be/6OuithZyBNg)
would you say that the fact that I advanced from no image to very bright image is improvement? or am I at the same stating point?
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Well, it's an improvement of sorts. So the metal cover I suspect is the heat sink for the microprocessor. The plastic "screws" are usually press-in from the top side.
On the reverse side you'll see a bulge in the plastic pin which you squeeze with long-nose pliers and work the pin out. Doubt if you need to do that though as all you'll mostly see is the top of the microprocessor. Does that metal cover get super-hot to touch and have you ever had an actual picture on the screen in its current state. Have you tried heating the main board in a household oven for 10 min. @ 180 deg. This used to recover LG main boards -albeit temporarily - but it doesn't seem to work on more recent LG tvs. Watched the video and my conclusion is main board or panel faulty, most likely panel if taping has resulted in some change to the display - not the Christmas joy you wanted.
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Hi Bruce
I wanted to thank you a lot for the time, the energy, and for being next to me in this journey of trying to fix a TV with no skills/tools on my part.
I kept a Beer in my fridge for 2 months and I said that I will open it when I will have a new TV
I don't have a new TV but I opened the beer yesterday since I manage to fix my broken TV. I am sure that without your advice and help I would have given up a long time ago.
the fix was: blocking 2 stripes on the Red cable after a lot of trying an error to find out which is the faulty stripe.
Thanks again, pal. I am proud of myself and also proud that there are good people like you.
Have a nice year
Hug.
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Glad my input was of help. Nothing wrong with that picture. Now it's beer o'clock but it looks like you've been at it already - that bottle looks like its been cracked open. Blocking LVDS strips is a somewhat arduous task. If I find it soon enough, then its too bad, so sad. Bruce