Bad T-con or bad panel??

[nomoresonys]

Re: Bad T-con or bad panel??

Here's Norcal diagnosing and dealing with a bad tab bond: https://www.youtube.com/watch?v=purk_SyiT44

[Alternet]

Re: Bad T-con or bad panel??

Ok, well that I think is normal, now try the other side if you get half a good picture with no distortion with each ribbon removed, then maybe it's not a panel issue.

will try that tonight and take pics.

[Alternet]

Re: Bad T-con or bad panel??

So a few questions before the results of the test.

Does anyone happen to know if this tv or tvs in general are color additive or subtractive?

I ask because when you unplug one of the sides that side goes white. Which means the R, G and B lcds are all set to 255 (or what ever number of bits tv's use now). That makes me think its color subtractive because no signal results in all colors (which equals white)

But when either side is plugged in that side goes black at boot up when the tv is showing which input is selected and the rest of the screen is black which means the R, G and B lcd's are all "closed" (not re-polarizing the light)

To me that would seem to indicate that every pixel on the screen is functional as it can operate both extremes.

Does this theory have any validity? Or are there other parts in modern panel circuitry that i'm not aware of?


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Now to the test results
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So when I first turned the tv on again I was fully expecting no picture (as I thought part of the issue might be that once things heated up thats what got things kind of working again)

I was wrong. The tv had full picture from cold boot but still half dark. But what I found more interesting was the OSD. It didn't seem to suffer from the darkness issue at all. (See pic1 and pic2)

What I also find interesting is that the darkness problem doesn't start exactly at half of the screen. It fades over. There is no hard line. (See pic1 and pic2)

Now once I popped the tv open and unplugged the "dark side" from the t-con I got pic3. I figured maybe there was a short again and it was just black. But slowly I started to see some sections of the screen changing. (See pic4)

It faded from pic3 to pic4 to pic5 over 2 seconds or so and I realized it is displaying the lg background pictures when no source is available. I waited a few seconds longer and it started to fade again (changing pictures). It faded in to pic6.


Side Note:

The fade effects of the OSD and pictures are standard, but I think they may be happening slower (or ghosting perhaps) on the "dark side". Its hard to tell since the picture is crappy



*****Edit*****

Also I forgot to mention something I found weird. While the power supply board makes a low buzzing noise (when the tv is on) which I attributed to the switching power supply noise. Once I turned the power off I noticed that both the large and smaller transformer made a ticking noise... while the tv is plugged in but powered off. I know there has to be standby voltage and there is power flowing. But I have never heard ticking like that when a tv is turned off. (see pic7 power board pic)

[budwich]

Re: Bad T-con or bad panel??

Your problem is that there is an issue with the drivers on the dark side. If the set had tabs on the panel along the side, then you would likely see / feel where the problem lies (ie. heating, burn marks, etc). However, on a set that has no side tabs, then the problem falls to signals (powering) not reaching embedded drivers on the panel itself. This is typically done with connections at each corner of the panel with connections associated with the bottom edge boards and the end bottom tabs. In your case, as your previous picture showed, there was a dark spot in the corner of the panel. This is the likely source of your problem. It is unlikely recoverable / repairable / saveable with any techniques discussed herein (ie. tape cutoff, tab removal). :-(

[nomoresonys]

Re: Bad T-con or bad panel??

Look at Norcal's video post #61, it's not a hard test and JUST may be your solution, I'm not ready to assume that it can't be fixed or at least able to render a decent display.

[Alternet]

Re: Bad T-con or bad panel??

Your problem is that there is an issue with the drivers on the dark side. If the set had tabs on the panel along the side, then you would likely see / feel where the problem lies (ie. heating, burn marks, etc). However, on a set that has no side tabs, then the problem falls to signals (powering) not reaching embedded drivers on the panel itself. This is typically done with connections at each corner of the panel with connections associated with the bottom edge boards and the end bottom tabs. In your case, as your previous picture showed, there was a dark spot in the corner of the panel. This is the likely source of your problem. It is unlikely recoverable / repairable / saveable with any techniques discussed herein (ie. tape cutoff, tab removal). :-(

I have questions.

***This is in no way trying to challenge what you have said. I just want to learn more then what I currently know***

The drivers manage to switch from black to white with no issue (which to me says they can drive all of the R, G and B's of each pixel. I would also assume that these two states don't rely on any feedback as its full on/full off kind of thing. Would this be correct?

Also when both sides are plugged in the OSD appears unaffected by what ever the issue is (the darkness). Does anyone have any idea why?

Also the biggest question I have that i'm hoping some one can answer. Why if its only displaying a very poor picture on that half of the screen when the good side is unplugged does it then start to display a completely valid picture that is just darker when the good side is plugged in?

When I saw this behaviour last night I started to think it was a feed back issue and that it cant adjust the colors properly to draw things due maybe a bad reference signal. (But again I do not have a background in lcd panel eng)

[Alternet]

Re: Bad T-con or bad panel??

Look at Norcal's video post #61, it's not a hard test and JUST may be your solution, I'm not ready to assume that it can't be fixed or at least able to render a decent display.

Ok i'll give it a shot tonight. I'll post results again tomorrow.

Any other tests I can run?

I'm also going to test all the resister and cap values on each panel driver board tonight and see if there is a difference between the bad and good side

[nomoresonys]

Re: Bad T-con or bad panel??

I'm thinking based on the picture that it's a bad/loose tab bond just a hunch not an assumption, never assume OR you make an ass out of u and me: a-s-s-u-m-e.

[Diah]

Re: Bad T-con or bad panel??

OOPPS.. i just take a look on yours others threat which described yours TV type LG UHD which it had tabs on the panel along the left and right side..you have panel fault .no fix for it :-(

[Alternet]

Re: Bad T-con or bad panel??

OOPPS.. i just take a look on yours others threat which described yours TV type LG UHD which it had tabs on the panel along the left and right side..you have panel fault .no fix for it :-(

Yes this tv has tabs that connect to nothing on the sides and tabs that connect to the panel driver which connect to the t-con on the bottom

So your thinking its garbage?

[Diah]

Re: Bad T-con or bad panel??

hope nothings are garbage to you... when it display some how pictures which could be satisfied one by trying around.. when you cover pin 44 the dark side become very bright.. trace the line of pin 44 on the tab boards of the panel dark side.. open the traced line and try to add resistances start with 1K .. you can use more or less res you may have brightness match the other side... this is theory i had never did it before.. because such fault always to me no fix for customers.

[Alternet]

Re: Bad T-con or bad panel??

I have another question... Say one of the tabs is bad and I had the skill to solderer and replace it. Is it possible to acquire one? or would you only be able to get one from another screen that is broken?

[Diah]

Re: Bad T-con or bad panel??

I have another question... Say one of the tabs is bad and I had the skill to solderer and replace it. Is it possible to acquire one? or would you only be able to get one from another screen that is broken?

well i do admire your spirit and will.. with this question am sure you could find way to fix yours panel .. always private users found many ways & Idea to others never try or thought about them,,, from my side wish you really good luck and successful.

[nomoresonys]

Re: Bad T-con or bad panel??

I see where diah is coming from, right it is considered unfixable for resale, what I'm trying to do is get a decent display and save it from the landfill if possible, I'm using a tv as monitor right now that I shimmed 5 years ago and gets used all day long, still going strong, doesn't have to be what's wrong with yours of course but it had the exact same shadow/ghost display.

[budwich]

Re: Bad T-con or bad panel??

Yes this tv has tabs that connect to nothing on the sides and tabs that connect to the panel driver which connect to the t-con on the bottom

So your thinking its garbage?

post a picture of the side tabs that you are referring to. There is some hope.

[nomoresonys]

Re: Bad T-con or bad panel??

It may also be a candidate for side tab removal, which Neil mentioned some 40 posts ago, that is if it has tabs on both sides, which is not reversible, there's a little light reading: https://www.badcaps.net/forum/showthread.php?t=49281

[nomoresonys]

Re: Bad T-con or bad panel??

There's a cof jumpering/bypass, not that hard once you grasp the principle, there's many many videos in all different languages, some explain better than others of course: https://www.youtube.com/watch?v=8o1WNiLr4_M

[budwich]

Re: Bad T-con or bad panel??

IF you have side tabs WITHOUT edge boards, then your problem is that the signals / voltages to the side tabs travel thru the panel "circuitry" from the bottom edge boards. You posted a picture a way back showing a "black spot" at the bottom corner of the panel. It is likely that area is causing problems for both the bottom and side. However, it is possible that you can get a "full image" with the removal of the side tabs as they appear to be "lacking drive" which then loads down the drivers on the other side of the panel. This results in the "dark side" that you are seeing. Once those side tabs / drivers are removed and are no longer loading down the opposite side, it is quite possible you may get a "full picture" that might be "relatively viewable" (ie. not golden eye"), assuming the forementioned spot is not a major panel issue (crack or otherwise).

[Alternet]

Re: Bad T-con or bad panel??

Sorry everyone. I had a super busy weekend and didn't get a chance to test the tv. Will test tonight and post results tomorrow

[Alternet]

Re: Bad T-con or bad panel??

So I tried to poke at the all the tabs and no such luck with anything.

I also noticed while doing this that there is most definitely lcd timing issue.

While poking all the ribbons on the side I noticed that when the stock lg background display picture changed I could see that some pixels close to the edge of the "dark side" took much longer to change then anywhere else.

For an idea of what this looks like, think of a the sweeping effect from one side to the other. Picture first changes on the one side and the change sweeps towards the other side.

Now this doesn't happen for the whole picture but as you go further and further towards the edge of the "dark side" thats what it looks like is happening. Depending on the picture I watch some pixels take as long as 5 seconds before they were updated with the rest of the screen.


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Also the attached picture show the side of my screen with the tabs that are connected to nothing. (as requested)