Vertical line/ribbon on LG TV

Scott_128

Commendable
Dec 21, 2016
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My TV is randomly doing the thing shown in the above pictures. It shows up at random and stays on for anywhere from a few seconds to a few minutes. And as can be seen in the second picture, it shows up even over top the popup menu at the bottom of the screen.

I contacted LG since my TV is still under warranty, and they gave me the name and phone # of a local repair shop to contact directly. They came out and replaced the main board but as can be seen in the above pics taken earlier this evening, the problem stiil exists.

It is an LG 50UH5530 if that makes any difference

I'll be contacting LG/repair company again but was wondering if anyone knew what the problem likely is?
 

maxwellmelon

Honorable
Oct 2, 2013
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this is a bad lcd panel. a basic tv has a main board that feeds a TCAS board. the TCAS board breaks down the main signal into sections and feeds it to the appropriate lcd driver/decoder. These drivers/decoders which are along the edge of the lcd panel itself (if you were to open it up they would be the little black areas along the flexible circuit ribbon that on the lcd panel edge because they connect directly to the pixel paths and cannot be replaced individually. in this case one has failed. the whole lcd panel will have to be replaced. if the TCAS circuit board failed your whole screen would look like that one stripe and would be a simpler fix

these drivers decoders exist because it uses less wires going from the mainboard to the lcd panel. otherwise the mainboard to lcd panel would have to have a wire for each vertical and horizontal row. its just simpler for them to feed the data to decoders in serial format.

and actually the decoder has not failed or there would be no image in that stripe so its just starting to fail.
 

maxwellmelon

Honorable
Oct 2, 2013
171
0
10,910
52
this is a bad lcd panel. a basic tv has a main board that feeds a TCAS board. the TCAS board breaks down the main signal into sections and feeds it to the appropriate lcd driver/decoder. These drivers/decoders which are along the edge of the lcd panel itself (if you were to open it up they would be the little black areas along the flexible circuit ribbon that on the lcd panel edge because they connect directly to the pixel paths and cannot be replaced individually. in this case one has failed. the whole lcd panel will have to be replaced. if the TCAS circuit board failed your whole screen would look like that one stripe and would be a simpler fix

these drivers decoders exist because it uses less wires going from the mainboard to the lcd panel. otherwise the mainboard to lcd panel would have to have a wire for each vertical and horizontal row. its just simpler for them to feed the data to decoders in serial format.

and actually the decoder has not failed or there would be no image in that stripe so its just starting to fail.
 

Scott_128

Commendable
Dec 21, 2016
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1,510
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Thanks, I figured that's what it was.

The repair company said originally on the phone is was probably a bad panel and that they would have to send someone out here to confirm it before LG would let them order it. Then they called me up to schedule the service appointment and said they were going to come out and replace the main board.

Guess they got pressured by LG to do try a cheap solution first to see if it would work since LG was going to have to foot the bill for this since it's under warranty.
 

Scott_128

Commendable
Dec 21, 2016
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1,510
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Now that line extends all the way to the right edge of the screen when it pops up...

So heard back from the repair company today via email, below is what they said word for word.

"Yesterday I spoke with TCC at LG regarding your TV problem. Explained what we attempted and they advised us to replace the LVDS ribbon cable. So I have ordered that LVDS 4/3."

What is the purpose of this LVDS ribbon cable?
 

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