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LG OLED 55b7v No video

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    #1

    LG OLED 55b7v No video

    Hello all

    My first post here.
    I have a LG OLED 55b7v which suddenly getting problem with no video.
    I have opend the TV up and found that the 24 v is missing on the output from the Power board.

    I have seen alot of posts related to similar problems but my Tv seems to behaves a little bit different
    I can turn the TV on via the remote and the TV starts to consume about 55 W but nothing happend. I can also turn it off via the remote via the remote.

    The Tv stays on when I turn it on. I cant see any red light from the optical output.

    As far as I can can mearure all outputs to the main board seems to be correct.

    Anyone having any ides how to resume the trouble shoooting .

    Isssues with powerboard, mainboard or Tcon card?? I do hope someone having any clue how to solve the problem. Anyone knowing common issues with those boards
    Attached Files
    Tags: None
    #2
    Re: LG OLED 55b7v No video

    plug out the 24V socket from T-CON driver boards side and turn on check the optical come on red or not.

    Comment

      #3
      Re: LG OLED 55b7v No video

      No differnce when disconecting the 24 V from the Tcon card
      I acctually noticed also that Im only able to turn off the panel via the remote about 30 secound after I started the TV.
      When I wait longer nothing happend and the TV remains turned on. I also notice tat the standby LED does not light anymore

      I suppose I need to meaurse the input to the main board again to verify input

      I suppose this is a indication of problem in the main board

      Comment

        #4
        Re: LG OLED 55b7v No video

        when you disconnect the 24V socket from T-CON side... you need to measure the 24V on power boards if it exist or not... if not you need first to take the power boards out and test it as stand alone to be sure it supply all needed voltage.

        Comment

          #5
          Re: LG OLED 55b7v No video

          Hmm, I erformed som measurements on the board but do not know what the correct values should be and if it concludes anything related to the problem.

          In operating mode:
          DPC = 0V
          ACD = 3,5 V
          PWR _ON = 3,5 V
          12 VM = 12 V
          20 VS = 20 V
          DRV_on = 0,07 V


          In standby

          DPC = 0V
          ACD = 0 V
          PWR _ON = 0 V
          12 VM = 7,6 V
          20 VS = 0 V
          DRV_on = 0 V

          My feeling is that the problem is related to the DRV_on signal which does not turn on the 24 V.

          Does this indicate anything which part to replace?
          What can I do to narrow this down more to replace the correct part or fixing the board?

          Comment

            #6
            Re: LG OLED 55b7v No video

            its okay... only you dont have DRV_ON which are responsible to turn on the 24V line.

            so if you want to check this 24V. you need just plug out the cable ( single wire ) from the socket 201 of DRV_ON .. and feed the pin of DRV_ON 3.5 V from PWR_ON ( 3.5V ) then turn on if the line 24V okay... it will exist.. and the screen will turn on too .... in case the screen had issue for example you can see it too.

            Comment

              #7
              Re: LG OLED 55b7v No video

              You have probably a bad standby software, must check for 25Q eprom and its dump

              Comment

                #8
                Re: LG OLED 55b7v No video

                Originally posted by Davi.p View Post
                You have probably a bad standby software, must check for 25Q eprom and its dump
                what standby software.... from where you got this name..... his tv turn on and there 3.5V PWR_ON. learn please before you give wrong advice.

                his issue related to MICOM. cut off DRV_ON. this can be bad panel or bad MB. if he disconnect the LVDS both... and the 24V come back then bad panel.... but some OLED can be repaired ( self test repair) if they got the 12 / 24V.
                Last edited by Diah; 03-18-2023, 04:26 PM.

                Comment

                  #9
                  Re: LG OLED 55b7v No video

                  When looping the 3,5 V from pwr_on to drv_on I got 24V from the powerboard so quite sure the powerboard is ok.

                  I noticed that I do nt have any power to the Optimal output or the USB connectors and no power to the standby led either so I suppose the issue is related to a bad main board.

                  Or could the T-con board be involved anyway in the problem?

                  Comment

                    #10
                    Re: LG OLED 55b7v No video

                    you have issue at 5V line on MB which it go to front LED wifi / BT. you need to check for short first at those module or terminated them one by one from system. then check.....

                    BTW i wrote before... disconnect the both LVDS and check
                    Last edited by Diah; 03-18-2023, 04:53 PM.

                    Comment

                      #11
                      Re: LG OLED 55b7v No video

                      I can add that the panel was replaced by LG due to burnt in issues just two year ago so it is a quite new panel. Ofcourse it could be broken .

                      Now I also tried to disconnect all cables between the T-con board and my mainboard and still no power to usb or optical output..

                      Is t possible to reset the main board sw in some way incase it went into some bad state?

                      Comment

                        #12
                        Re: LG OLED 55b7v No video

                        yes in case it response on IR signal from outside.... send IN_STOP command with IR DIY or mobile with IR and follow it with code 0413 it should go to STB plug iut from wall 1 minute then turn it on

                        Comment

                          #13
                          Re: LG OLED 55b7v No video

                          Service Manual
                          Attached Files

                          Comment

                            #14
                            Re: LG OLED 55b7v No video

                            atleast it respond to power on / off via the remote.

                            Hmm sorry Im a real rookie when it come to TV repair. Could you advise me what I need.
                            I have some old mobiles which I think support IR, Can I download an app doing the trick

                            Sorry for my beginner questions

                            Comment

                              #15
                              Re: LG OLED 55b7v No video

                              try this from my old post

                              Comment

                                #16
                                Re: LG OLED 55b7v No video

                                Diahrrea don't break my balls i know what i wrote, i have to learn nothing by you, i confirm my diagnosis, i've seen now the mb photo, there is probably a standby mpu near switch SW300 , so no 25Q chip, that it must be rewritten, how? You need a programmer that manage it, if not mb replacement, bye
                                Last edited by Davi.p; 03-19-2023, 03:43 AM.

                                Comment

                                  #17
                                  Re: LG OLED 55b7v No video

                                  Hmm, I have performed some measurments . It does not seem to be any shortcut to ground , atleast nothing I found but still no 5V power on the board
                                  I have verified bot 12v and 20 v incoming on the board.
                                  Anymore advise what to check or do I need a new mothercard?

                                  Comment

                                    #18
                                    Re: LG OLED 55b7v No video

                                    can you program??

                                    Comment

                                      #19
                                      Re: LG OLED 55b7v No video

                                      slightly but I do not think I manage on this level..
                                      Do you know anyone which have the knowledge...

                                      Comment

                                        #20
                                        Re: LG OLED 55b7v No video

                                        Originally posted by nicke74 View Post
                                        slightly but I do not think I manage on this level..
                                        Do you know anyone which have the knowledge...
                                        disconnect socket P4000 on the MB.. and plug it in... you need to follow all part with FL name.. measure from both side with reference to TV chassis

                                        any strange reading marked it on photo to the part section and upload here.

                                        Comment

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