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    55ub850v no picture

    Hi

    I could do with some advice.

    Ive got a 55ub850v tv which turns and stays on, with backlights and sound but no picture.

    The fuse on the the tcon has 11.78v on both sides.

    There is also voltages on I assume test points at the bottom right hand corner of the tcon. There is also voltage present on the bottom left corner which fluctuate.

    I have checked the (as much as I can) the components on the screen boards. They seem fine.

    The psu output voltages are fine. The chips on the tcon is not very warm- whilst the main chip on the main board is hot-ish.

    I was wondering if anyone could advise on what to check next or what they suspect is faulty?

    I was going to change the main board.

    Thanks in advance
    Attached Files

    #2
    Re: 55ub850v no picture

    What do you get on the screen if you have only one ribbon cable connected one at a time between T-CON and the tab boding board?
    BTW, pictures are too out of focus to see Voltage test points on that T-CON board.
    Last edited by budm; 04-30-2018, 09:45 PM.
    Never stop learning
    Basic LCD TV and Monitor troubleshooting guides.
    http://www.badcaps.net/forum/showthr...956#post305956

    Voltage Regulator (LDO) testing:
    http://www.badcaps.net/forum/showthr...999#post300999

    Inverter testing using old CFL:
    http://www.badcaps.net/forum/showthr...er+testing+cfl

    Tear down pictures : Hit the ">" Show Albums and stories" on the left side
    http://s807.photobucket.com/user/budm/library/

    TV Factory reset codes listing:
    http://www.badcaps.net/forum/showthread.php?t=24809

    Comment


      #3
      Re: 55ub850v no picture

      If I remove the one ribbon or both of them the screen still remains blank - I hope the attached photo of the voltages for the test points on the tcon (bottom right hand corner).

      If I remember correctly they read between 1.2v to 13.9 and were static but not 18v.

      There are no voltages written on the bottom left hand corner of the tcon.

      When I removed the two ribbon cables from the tcon the voltages read the same.

      Sorry really struggled to get clear focused photos
      Attached Files
      Last edited by thuss; 05-01-2018, 04:25 AM.

      Comment


        #4
        Re: 55ub850v no picture

        Bottom Left hand side of tcon
        Attached Files

        Comment


          #5
          Re: 55ub850v no picture

          Check the LVDS with an oscilloscope. See if the main board puts anything out. Also check to see if the panel is getting any power.

          Comment


            #6
            Re: 55ub850v no picture

            no havent got a scope - the main board is getting power and then in return feeds power to the tcon hence the 11.8 v on the fuses.

            Would the next step be to remove the Lvds and supply 12v to tcon fuse and connect vcc to pin 41?
            Last edited by thuss; 05-01-2018, 06:00 PM.

            Comment


              #7
              Re: 55ub850v no picture

              https://www.badcaps.net/forum/attach...3&d=1525142506
              https://www.badcaps.net/forum/attach...0&d=1525170610
              I still cannot see much test points on that inverter board, I cannot read the P/N on the barcode sticker and the P/N as printed on the board.
              BTW, what brand is this 55ub850v?
              Last edited by budm; 05-01-2018, 10:27 PM.
              Never stop learning
              Basic LCD TV and Monitor troubleshooting guides.
              http://www.badcaps.net/forum/showthr...956#post305956

              Voltage Regulator (LDO) testing:
              http://www.badcaps.net/forum/showthr...999#post300999

              Inverter testing using old CFL:
              http://www.badcaps.net/forum/showthr...er+testing+cfl

              Tear down pictures : Hit the ">" Show Albums and stories" on the left side
              http://s807.photobucket.com/user/budm/library/

              TV Factory reset codes listing:
              http://www.badcaps.net/forum/showthread.php?t=24809

              Comment


                #8
                Re: 55ub850v no picture

                its a lg tv and please see attached photo where I tested the voltages on the tcon

                The part number is also on the photo
                Attached Files

                Comment


                  #9
                  Re: 55ub850v no picture

                  as far as I can make out the p/n 6807-0502c thats all there is on the board there is no additional stickers.

                  The second part number maybe 6871E - 3703M?

                  I assumed they were test points
                  Attached Files
                  Last edited by thuss; 05-02-2018, 09:39 AM.

                  Comment


                    #10
                    Re: 55ub850v no picture

                    LG 6871L-3703M (6870C-0502C) T-Con Board.
                    There many power supplies Voltages that need to be tested.
                    Pictures provided by shopjimmy.
                    Attached Files
                    Never stop learning
                    Basic LCD TV and Monitor troubleshooting guides.
                    http://www.badcaps.net/forum/showthr...956#post305956

                    Voltage Regulator (LDO) testing:
                    http://www.badcaps.net/forum/showthr...999#post300999

                    Inverter testing using old CFL:
                    http://www.badcaps.net/forum/showthr...er+testing+cfl

                    Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                    http://s807.photobucket.com/user/budm/library/

                    TV Factory reset codes listing:
                    http://www.badcaps.net/forum/showthread.php?t=24809

                    Comment


                      #11
                      Re: 55ub850v no picture

                      Thank you for that - would they range from say 1v up to a max of 24V?

                      Comment


                        #12
                        Re: 55ub850v no picture

                        Originally posted by thuss View Post
                        Thank you for that - would they range from say 1v up to a max of 24V?
                        Voltage range of what test points?
                        Just report Voltages of all those test points, make sure to put down the name and follow by the Voltage reading.
                        Last edited by budm; 05-02-2018, 10:41 AM.
                        Never stop learning
                        Basic LCD TV and Monitor troubleshooting guides.
                        http://www.badcaps.net/forum/showthr...956#post305956

                        Voltage Regulator (LDO) testing:
                        http://www.badcaps.net/forum/showthr...999#post300999

                        Inverter testing using old CFL:
                        http://www.badcaps.net/forum/showthr...er+testing+cfl

                        Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                        http://s807.photobucket.com/user/budm/library/

                        TV Factory reset codes listing:
                        http://www.badcaps.net/forum/showthread.php?t=24809

                        Comment


                          #13
                          Re: 55ub850v no picture

                          will do thanks

                          Comment


                            #14
                            Re: 55ub850v no picture

                            Had two of this model both with the issues you describe in the last couple of months both were caused by faulty main boards. In both instances a replacement main board resolved the problem.Also from what I remember the 49" board will also work with no adjustments.
                            Hope this helps.

                            Comment


                              #15
                              Re: 55ub850v no picture

                              Hi

                              Sorry about the late response. The readings on the tcon were as follows

                              v18-1.6mv
                              v15-1.9mv
                              v14-1.7
                              v12-1.6
                              v10-1.6
                              v9-13.4
                              v7-13.5
                              v5-13.5
                              v4-13.7
                              v1-13.7mv
                              vdd- 1.74v
                              vcourfb- 1.7
                              vcc18- 1.6
                              vglI- 18.3
                              VIN- 11.78v
                              VGH - 1.5mv
                              VDD - 0.7
                              VCOM2- 22mv
                              VCOM1- 22mv
                              VCORE- 1.5mv
                              VGH_R- 1.4mv
                              VGH_even- 5.8mv
                              VGH_ ODD- 5.7mv


                              I think its the screen but any advice would be appreciated. I changed the main board still has the same symptoms. i.e No picture (the replacement board was out of a broken 49ub850v screen tv with a display).

                              Comment


                                #16
                                Re: 55ub850v no picture

                                I also swapped my main board (from 55ub850v) into the broken screen 49ub850v turns on and displays a broken picture.

                                I also swapped the tcon out of the broken screen 49yb850v into the 55ub850v but still no picture

                                Comment


                                  #17
                                  Re: 55ub850v no picture

                                  Originally posted by thuss View Post
                                  I also swapped my main board (from 55ub850v) into the broken screen 49ub850v turns on and displays a broken picture.

                                  I also swapped the tcon out of the broken screen 49yb850v into the 55ub850v but still no picture
                                  Guess it's possible that the tcon from the 49 isn't a match for the 55?
                                  Last edited by nomoresonys; 05-16-2018, 08:48 PM.

                                  Comment


                                    #18
                                    Re: 55ub850v no picture

                                    One thing to try, put the 49 tcon back in the broken screen and see if it still has the picture, a lot of times a bad panel will kill a tcon. Did you try the tcon from 55 into 49?

                                    Comment


                                      #19
                                      Re: 55ub850v no picture

                                      Originally posted by thuss View Post
                                      Hi

                                      Sorry about the late response. The readings on the tcon were as follows

                                      v18-1.6mv
                                      v15-1.9mv
                                      v14-1.7
                                      v12-1.6
                                      v10-1.6
                                      v9-13.4
                                      v7-13.5
                                      v5-13.5
                                      v4-13.7
                                      v1-13.7mv
                                      vdd- 1.74v
                                      vcourfb- 1.7
                                      vcc18- 1.6
                                      vglI- 18.3
                                      VIN- 11.78v
                                      VGH - 1.5mv
                                      VDD - 0.7
                                      VCOM2- 22mv
                                      VCOM1- 22mv
                                      VCORE- 1.5mv
                                      VGH_R- 1.4mv
                                      VGH_even- 5.8mv
                                      VGH_ ODD- 5.7mv


                                      I think its the screen but any advice would be appreciated. I changed the main board still has the same symptoms. i.e No picture (the replacement board was out of a broken 49ub850v screen tv with a display).
                                      T-CON board is dead, it has 12V feeding it but lots of Voltages are really really low. Do you get the same readings if the cables between T-CON and LCD panel are removed. The board may not be compatible with your screen, also can be bad panel that causes lots of Voltages on T-CON to be low.
                                      Never stop learning
                                      Basic LCD TV and Monitor troubleshooting guides.
                                      http://www.badcaps.net/forum/showthr...956#post305956

                                      Voltage Regulator (LDO) testing:
                                      http://www.badcaps.net/forum/showthr...999#post300999

                                      Inverter testing using old CFL:
                                      http://www.badcaps.net/forum/showthr...er+testing+cfl

                                      Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                                      http://s807.photobucket.com/user/budm/library/

                                      TV Factory reset codes listing:
                                      http://www.badcaps.net/forum/showthread.php?t=24809

                                      Comment


                                        #20
                                        Re: 55ub850v no picture

                                        Originally posted by budm View Post
                                        T-CON board is dead, it has 12V feeding it but lots of Voltages are really really low. Do you get the same readings if the cables between T-CON and LCD panel are removed. The board may not be compatible with your screen, also can be bad panel that causes lots of Voltages on T-CON to be low.
                                        +10 Bad panel sorry to say. With 12V supply coming in and getting only mV on several of those test points, it would appear that either the T-CON is not working as previously stated or the Panel. I suspect the Panel though.

                                        Comment

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