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2022 Model TCL LCD TV with Roku interface

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TCL 75" 5 series TV (S555) with one quarter of screen dead.

Hello guys. I'm sorry that I don't know all the terminology, but I have a problem that I hope won't be too involved. Also, this this TV was in a factory where it almost definitely has been sprayed with water.

I have a 2022 TCL 75 inch 5 series LCD TV model 75S555 with a display problem that would manifest itself in different ways. Sometimes only the left half of the display was totally black, and other times it would flicker with white lines throughout. During a little troubleshooting I found that the ribbon cable from the TConn board (I think that's what it is. It is centrally mounted and has 1 ribbon cable leading from another board and 2 larger ribbon cables leading toward the bottom of the TV) had some corrosion on 4 or 5 of the pins. I cleaned the corrosion from the ribbon cable and I cleaned the connector as well as possible with contact cleaner. During testing I found that the problem then affected the whole screen. When disconnecting the ribbon cable in question I found that the right half of the screen functioned normally and when I reconnected the cable it would take out the whole screen. The faulty cable led to a board with several permanent ribbon cables which seem to lead to the actual LCD panels, and it also had a "jumper" ribbon cable connecting it to another nearly identical board. When disconnecting the "jumper" I found that the right 3/4 of the display worked normally. So the problem is definitely the board which serves the left-most quarter of the screen. I'm afraid the the LCD panel itself is trashed, but my question is whether this sounds like something that can be repaired. I will attach some photos of the components in question, and thank you all for your time.

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Edit 3/17/24

@oldturkey03 advice, I masked off the smaller groups of wires one at a time until the rest of the screen functioned fine. In my case it was the third small group of contacts from the center. Unfortunately I did not take a picture of the tape placement while the ribbon cable end was detached, and I'm scared to touch it again, but I will attach a photo to the original question showing the installed cable and which set of pins I taped off. Hopefully this might help someone else in the future.

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Beantwoord! Bekijk het antwoord Dit probleem heb ik ook

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@travisgray93425 those long skinny boards are your LCD driver boards. You are right, those ribbon cables connect right to your :LCD those boards are not replaceable by a DIY'er and are considered part of the panel. The second picture shows the LED driver board (where the screwdriver points to). That is basically what provides the power to light up your screen.

Those ribbon cables in picture number 4 look rough. I would actually consider replacing them. If I understand your narrative correctly, it works okay until you connect the left driver board. Then it all goes downhill. If so, you know the issue is on the Left driver board. It looks like there are small ribbon cables that connect the driver boards. Those can tear as well and are known to cause issues like the one you describe. If you can, post a couple more pictures of the driver boards and let us know if there are 2,4 or 6. Also, one more picture of the board where those two black ribbon cables originate from. I predict that you have no separate T-con board but your T-con circuitry is integrated into the main board.

A tape-off may actually fix this (85% chance)

Update (03/16/24)

@travisgray93425 not a legend just an old dude trying to safe the world :-) You can't use a multimeter for those ribbon cables since they are data lines. We would need an oscilloscope and the proper information about what data goes over those lines.

Check the flex cables that daisy chain the driver boards (like the one in your image CS F04-1). Those love to tear and shorten out the data lines as well. Do not forget to clean the inside of all of the the connectors. Use either some +90% isopropyl alcohol; or some non-conductive contact cleaner on the one that you know is trouble already.

A tape off refers to blocking the signal on the faulty data lines with a strip of tape. It's not an exact science and works about 85% of the time. It's time consuming since you would have to tape off the data lines on the side that is known to give you trouble (left in your case). Check the YT videos https://www.youtube.com/watch?v=pfrRhw7-... and https://www.youtube.com/watch?v=atNmhu7H... for an idea about the Tape-off

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Thank you very much for the quick response! I actually recognize your user name from several Google searches and I'm honored to be talking to a legend. You understand correctly; the right 3/4 of the screen look fine when the last driver is disconnected and then they go out when I connect it. I had planned to replace the ribbon cable because in addition to the corrosion, the pins seem to have delaminated from the substrate on the cable and are finicky to get seated without bending out of place.

There are a total of 4 driver boards. The main board connects to the two inner boards, and each of the inner boards daisy chains to an outer board. The corroded socket is actually on the inner board where it connects to the main board, though that particular board and its portion of the display work fine so I suspect the socket will be okay, and every other ribbon cable looks like new. When you say tape-off, I assume you mean there is a short in one of the circuits and I need to isolate it?

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Is it possible to test each for continuity to ground (or some kind of 0V?) rather than by using trial and error? I'll add the additional photos as soon as I can see how. Thank you again.

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@oldturkey03

Thank you so much! You just helped me save a 10 month old TV from going to the trash. I masked off the smaller groups of wires one at a time until the rest of the screen functioned fine. In my case it was the third small group of contacts from the center. Unfortunately I did not take a picture of the tape placement while the ribbon cable end was detached, and I'm scared to touch it again, but I will attach a photo to the original question showing the installed cable and which set of pins I taped off. Hopefully this might help someone else in the future. Thank you again!

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@travisgray93425

No! don't touch it :-) Leave well enough alone!!!! Glad you got it fixed and glad we kept another device from going to the landfill. Awesome job!

Repair is War on Entropy!

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Travis Gray zal eeuwig dankbaar zijn.
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