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LG TV has weird flickering blue cast on picture

Recently, my LG49UH610T 4K TV started flickering - it isn't the backlight but one of the colours flickering on and off, leaving the screen with a mostly blue colour.

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This flickers on and off constantly (but these days it is mostly blueish)

Weirdly, there is a narrow stripe at the top of the screen that is still the right colours:

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I have already tried reattaching all the ribbon cables on the boards, and then bought a T-Con board off e-bay but that didn't fix it (actually, maybe it made it worse, so perhaps it was a dud). I then replaced the controller board but that made no difference.

My question then is what to try next - should I get another T-Con board and hope that it works? Or is it likely to be something else going on?

Edit - adding some photos of the boards.

6870-584B T-CON board

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EAX66943504 main controller

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EAX66923201 Power supply board

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Overall arrangement:

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Closeup of T-CON board

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Connection to screen

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Update 1 Mar 2023

After replacing the T_CON board, the screen is not flickering, however the colours remain distorted.

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There is a narrow strip along the top of the screen which is uncorrupted

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Update 2 Mar

Here is the screen when removing one of the pair of ribbon cables coming out of the T-CON board.

1 Removing the cable on the left

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2 Removing the cable on the right

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cwthorpe under any other circumstance, I would go with a T-con board as well. This looks like a bad Gamma IC. Now depending on your panel, there can also be a Gamma IC on those boards. Those are the boards that are directly connected to the panel. The ones the T-con board connects to. Let us know which board your changed here "I then replaced the controller board". I am not certain what you mean by controller board. Anyhow, try another T-con board,. After that we need some really good pictures of the LCD driver boards to see if we can identify if this one has a Gamma IC,

Update (02/07/2023)

cwthorpe I marked the points with red arrows. Let's see if we can find out whats going on with this.

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14 Comments:

thanks. I have just ordered another T-con board 6870C-0584B from a different supplier, maybe it will work :)

Will upload some photos of the boards. The "controller board" is the main CPU board. I didn't touch the boards connected directly to the LCD - they are under the bottom edge of the TV.

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@cwthorpe okay so the one you replaced is the main board. Yes, those boards under the bottom edge are the once we may have you take a look at. Those are a pain since they are attached to the panel via a special process and are not meant to be replaced/fixed/etc. by the DIY'er :-( but nobody says we cannot get you to replace an IC :-))

If you have a multimeter and a steady hand, we might be able to get the Gamma Voltages for your T-con board. You could see if it has the right voltages. We need a really good clear picture of the T-con board. OR we could just wait till you get the new board :-)

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Hi @oldturkey03, thanks - I have updated some clearer pictures. I do have a multimeter but nothing more, so could make some measurements if that would help.

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Here are the measured voltages:

VGL1 -6.9V

VGL2 -15V

VGH 28V

Vcc 3.3V

Vcore 1.22V

VDD 16.4V

Vcc18 1.8V

F1 12.8V

VGH_even flips between 28 and -15V about every second

VGH_odd same

Vcom1 4.6V

Vcom2 4.6V

VcomRFB 4.68V

Do these measurements indicate anything?

Cheers!

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@cwthorpe VDD is the Gamma IC control and it has the correct voltage. The rest looks pretty close to the data I have Vcom lines are a little lower than what I have. I get between 5.9 and 5.6 but that may be negligible. Glad the voltages are there but we'll just have to see what your new board shows.

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cwthorpe will be eternally grateful.
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