2012 LG 55" - picture distorts every two seconds
 

Has anyone seen this on an LCD set and know what it is? The picture looks normal for 2-3 seconds then "pulls" down and distorts like there's a ghost image for another 2-3 seconds . This repeats indefinitely. The top 1/16th of the screen stays normal. If it's a problem with a board, I'll start looking for one, but if it's the display then I guess I need to say c'est la vie and get rid of it. It's model 55LS579C-UA. Any knowledge is appreciated!

Most likely a panel failure. gate driver on the left or right of the panel. Try removing one ribbon from tcon to panel. there should be two of them. If still an issue repeat on opposite side.

9Sometimes applying a little heat gently to the left and right of the panel will temporarily straighten it out.

But first, get an image on the whole screen. is there a vertical line where above or below this line it's fine and doesn't exhibit this issue?

Thanks for the tips. There's a fixed horizontal line about 1/16th from the top where everything above it stays fine, and everything below has the issue.

When I unplug the left ribbon of the tcon board (left facing the front of the set), the left of the screen is white, and the right continues on with the issue.
When I unplug the right ribbon, the right of the screen is white and the left is a colorful rainbow. When I reconnect them both, it returns to how it was. I powered the set off before disconnecting/reconnecting.

The pictures showing the full screen are from the picture test function in the menu.

There's a vertical line on the right side that's always there. The only time it wasn't visible was when I disconnected the right tcon cable.

I warmed up each side of the display (both front and back) with a hair dryer and it didn't help.

Is the line present on the left even through the colorful rainbow look? That's for sure a failed gate driver. (most likely on right side) on panel under the plastic trim a d a metal housing.

No. If it's present, it's not visible to me. I did notice that the vertical line on the right is barely visible when the right ribbon is disconnected, after all.

Then it's a shorted gate tab failure right side right where the line is. However in my experience with flatscreens (repaired about 200 or so), this may be repairable even though the lcd panel is defective.

You need to remove the bezel and the side metal shield from the panel, exposing the panel edges.

I put the set face down on three pillows, removed the bezel and right side metal shield, and this is what I see.

Flip it right side up carefully and pull up on the plastic clips in the area of the line. Then look for some driver attached to the side of the panel. Is there one there?

This is as much as I can see without removing more plastic clips.

Ok. This panel does not have the gate drivers. Its controlled by the vertical gate drivers that are embedded in the vertical drivers.


There is a crazy method of using scotch tape and putting it over a few pins on the right ribbon that goes into the panel from the tcon. It may work. You have to try to cover a few pins at a time starting from right to left. each time you go to remove the tape, turn the TV off first.

Hopefully this makes sense. essentially you will be removing the affected short by covering it up. The panel will then rely on the opposite gate to control the vertical timing signals.

You're a genius. Covering up some of the pins with tape stopped that repeating distortion, but it introduced some new artifacts. There are "sparkly" dots here and there throughout the picture and what look like wide scan lines on the right side.

Unfortunately the stationary vertical and horizontal lines are still present, so my guess is that those are there to stay, even if I could tweak the tape to eliminate the artifacts. If you think otherwise, I'll try again.

It's definitely watchable now, and I learned something, so thanks for the help! :thmbsp:

Unfortunately that's a drawback. now the panel relies on the opposite driver. The line is there to stay. It's the original dead spot now. The scan lines may be there for good now. Or one too many pins covered up. But most likely there to stay.

This "fix" shut down the horizontal timing signals of those particular drivers

Glad to hear it helped!

You could try tweaking the tape around but the vertical purple line that you see about 3/4 from the left may be the defunct driver, missing the horizontal gate signal and not passing it on to the next in series. but maybe you could get those sparkles out and the ghost lines better. It's a crapshoot with a panel that only has vertical drivers to scan the horizontal as well. Double the heat. Double the failure.

It's already put back together, and after watching it for a few hours last night, the purple vertical line is more distracting than the new issues, so I think I'll leave it as is. Like you said it's a crapshoot anyway. And if the vertical driver is running twice as hard to compensate, it's probably not a permanent solution, so out to the garage she goes. It'll make a good set for occasional use out there. Thanks again for helping me fix an unfixable set!