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Thick black line down center of screen, PN50A400C2DXZA

I received a 55in QLED Samsung television. It has a vertical 3/4” black bar down the center of the screen. I have tried cleaning and re-seating every connector and tab on the back. At one point I produced horizontal lines but remedied them by cleaning the tabs an additional time. I’ve done every bit of clean up I can muster on the back, but the thick black line remains.

The line doesn’t flicker, doesn’t change color or size when pressing on the screen. The screen is glass, so massaging it doesn’t produce any results other than cleaning it further.

Running the pixel shift tool from the tv’s menu produced no results, line doesn’t budge.

Resetting to factory does nothing.

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This is a screenshot from a youtube video, however it looks to be exactly the same as the TV I was working on from the back. In the video, I’ve performed all the re-seating and cleaning this user suggests. link: https://www.youtube.com/watch?v=LRVZytbQ...

I am looking for any additional troubleshooting steps I may have missed and suggestions.

Thanks,

PlainText

Update (11/10/2019)

Thanks for the quick reply @oldturkey03.

The issue persists across all input and I’ve pushed on each of tabs circled in this picture, while it was on and saw no change. I’m not sure what to do next.

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Answer this question I have this problem too

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I have this wide vertical line going down the middle of my TV how did you fix yours I need the same

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@palanddd Thick black lines are commonly caused by a failed connection between the panel and the LCD driver board. What is your TV's make and exact model? Anything happen to that TV or did this just start all of a sudden?

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@plaintext87 The PN50A400C2DXZA should be a 720P plasma television not a QLED. You are describing the line as “running down” the screen (vertical) but everything else you refer to (video link etc.) is horizontal. Can you clarify this? Does it go up and down (vertical) or left to right (horizontal)? Most of the time a thick black line is caused by a total loss of communication between the board and the panel. The lines most likely originate from the E and F buffer boards. The connections from these boards to the PDP Panel are a bonded connection. Push on the TAB (flat ribbon cable) that enters the panel and see if it makes a difference. Of course you do want to check to make sure that you have this line with all input sources as well as your onscreen menu.

Update (11/10/2019)

@plaintext87 while I am looking over your images (your exact model correct? I noticed it’s a screen capture) I added a quick identifier for the boards. That way we are all on the same page. Check where I marked the ? mark since there are no clear X-buffer boards ( I believe Samsung refers to them as E, F and G buffers). I wonder what’s hiding under that area.

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I expect to see some buffer boards under there

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Quick explanation of the functions

SMPS(Switching Mode Power Supply)

 It is the supplier to provide voltage and current to work the drive voltage and panel in each board.

X-MAIN BOARD

 It makes the drive wave form by switching FETs to Timing Control coming from logic-board and supplies X electrode of panel with the drive waveform via connector.

The X-sus’ purpose is to create/deliver the picture in Vertical Bands. When those go bad, you get a normal picture, but you also get BANDS of vertical that are black or bands of noise about 2 inches wide.

Y-MAIN BOARD

 It makes the drive waveform by switching FETs to Timing Controller coming from the logic-board and provides Y electrode of panel with  the drive waveform via Scan Driver IC on Y buffer board  in order.

MAIN BOARD

It process image signal and performs buffering of the logic-main board (to create XY drive signal and output) and the address driver output signal. Then it supplies the output signal to the address driver IC(COF Module).

LOGIC BUFFER(E,F,G)

It delivers the data signal and control signal to the COF.

Y-BUFFER (Upper,Lower)

 It is the board to impress the scan waveform on the Y board and consist of 2 boards    (upper board and lower board).

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1 Comment:

Thanks for the reply, sorry for the slow get back to you about it. Holidays been crazy.

So I only mentioned horizontal lines because while cleaning the TV I created horizontal lines and were able to remove them by doing another cleaning.

My problem is a inch thick black bar that is vertically down the center of the screen.

As for the screenshot, yes in my post I mentioned this was a screenshot but it looks very similar to the tv while I had it open.

From your description it sounds like my X-Main Board needs replaced, as the picture is perfectly fine except for the thick black bar down the center.

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