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LG 65UJ6300 no backlight unless TCON disconnected.

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    #1

    LG 65UJ6300 no backlight unless TCON disconnected.

    Full model of the TV is 65UJ6300-UA.BUSYLOR. TV was given to me by a relative as non-operational so I'm trying to get it working so I have a nice cheap upgrade for my living room. This is my first TV repair so if it sounds a little like I know what I'm talking about, I don't.

    TV turns on and has audio, but backlight doesn't turn on. Getting 230v from LED+ to chassis. Also can't see anything with flashlight test. Another forum suggested I replace the LED strips because that's the most common failure on LG TV's and the flashlight test doesn't always show results.

    Replaced LED strips. Powered TV on with TCON disconnected so I can test to see if the LED's were working before reinstalling panel, and they came on. Reassembled TV. Same problem as before. Disconnected TCON from main board again, backlights come on. Reconnected TCON to main and then tried disconnecting the two cables from TCON to panel. No lights.

    So basically the backlights only come on with the TCON disconnected from the main board.

    So....bad TCON?

    I tried finding a schematic for this TV and came up with nothing. I did find a repair manual for one that uses the same power supply board and did voltage tests according to that and everything seems in spec. Any help would be appreciated.
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    #2
    Re: LG 65UJ6300 no backlight unless TCON disconnected.

    what are the voltages BLon and DIM signals? It does appear a TCon fault. If you can find a cheap Tcon, try it!

    Comment

      #3
      Re: LG 65UJ6300 no backlight unless TCON disconnected.

      Disconnect cables from Tcon to panel one at the time. And make sure they are connected properly.

      Comment

        #4
        Re: LG 65UJ6300 no backlight unless TCON disconnected.

        Originally posted by CapLeaker View Post
        what are the voltages BLon and DIM signals? It does appear a TCon fault. If you can find a cheap Tcon, try it!
        I don't know where the BLon and DIM signals are. The only thing I was able to find is a repair manual from a different TV that happens to use the same power supply board (image attached). There's only the single 12 pin connection going between the power board and the main board and none of the pins are labeled backlight or dim. Maybe it's the MS level pin on pin 11? Idk. Or more likely PDIM on Pin 12 but I don't know what it's supposed to be. All of those voltages the manual describes at least check out in any case except P801 1-7 which makes sense because the backlight isn't on.

        Also it should be noted that TV who's repair manual I'm using doesn't appear to use a TCON board (must be all built into the main board) so there aren't any helpful diagnostics I can use.

        Originally posted by alfatv
        Disconnect cables from Tcon to panel one at the time. And make sure they are connected properly.
        Tried that already.


        I'm just going to go ahead and order the 3-board set and see what happens. It's cheap enough.
        Attached Files

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          #5
          Re: LG 65UJ6300 no backlight unless TCON disconnected.

          Originally posted by BakaMonogatari View Post
          Tried that already.


          I'm just going to go ahead and order the 3-board set and see what happens. It's cheap enough.
          And the result was? If the driver board is at fault then you're just wasting money buying boards.

          Comment

            #6
            Re: LG 65UJ6300 no backlight unless TCON disconnected.

            Originally posted by diif View Post
            And the result was? If the driver board is at fault then you're just wasting money buying boards.
            The result was the same. Left one only disconnected, right one only disconnected, both of them disconnected. Same result. No backlight.

            Comment

              #7
              Re: LG 65UJ6300 no backlight unless TCON disconnected.

              I just changed backlights on the same TV.
              I also saw no backlights and TV turning off after connecting LCD.
              Besides cables from T-Con, there are 2 other flex cables connecting sections of long boards to LCD.
              Make sure all cables are connected properly, it worked for me.

              Comment

                #8
                Re: LG 65UJ6300 no backlight unless TCON disconnected.

                Just figured I'd post the conclusion. It was the TCON. Works perfectly now. Wish I didn't put myself through the trouble of changing the LED's for no reason but that was a $30 and a couple of hour mistake. At the end of the day it cost me less than $100 to fix this TV I got for free so I'm happy.

                Comment

                  #9
                  Re: LG 65UJ6300 no backlight unless TCON disconnected.

                  Originally posted by BakaMonogatari View Post
                  Just figured I'd post the conclusion. It was the TCON. Works perfectly now. Wish I didn't put myself through the trouble of changing the LED's for no reason but that was a $30 and a couple of hour mistake. At the end of the day it cost me less than $100 to fix this TV I got for free so I'm happy.
                  Hey there what was the model number for the T-Con board and where did you get it?

                  Comment

                    #10
                    Re: LG 65UJ6300 no backlight unless TCON disconnected.

                    6870C-0689A was the one that was in my TV and I got it from shopjimmy.com. Be aware that the TV can also come with 6870C-0750A which is incompatible. You need to check which number you have and make sure you get the right one.

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