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42lg3000-za No Picture but got sound

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    42lg3000-za No Picture but got sound

    I got hold of a 42LG3000, it has sound but no picture. Ive removed all the boards, did a visual check & cant see anything wrong.

    I like some help into how i can test the boards to see they are all working correct.

    I did try get the schematic but cant get to download as the page wont load for me? It was working for me the other day when i downloaded a schematic from the same site.


    I dont know were to put the probes on the board, an what the readings should be on my meter.

    I have not got a camera, but i most def will be getting one, i know it is well needed in these types of situation.

    #2
    Re: 42lg3000-za No Picture but got sound

    Hi Pictures are really important as probably most of us will not have seen inside this set.
    Did you try and download from here http://elektrotanya.com/lg_42lg3000_.../download.html you can only download two items per day unless registered and if you are impatient and double click then thats it. Try again switch off an adblockers and wait a minute after the page has loaded then click get manual near the bottom right hand side.
    First sort of test might be to test for expected voltages on all the power supply output voltages. With it all connected up and switched on Meter on vDC200 black probe on chassis ground screw check each pin with red probe. report results like
    CN1
    Pin 1 24v actual 24.1
    Pin 2 12v actual 11.5v
    PSON actual 3.2v etc etc

    Care do not touch heatsinks or primary side with body or probes. I have not got the sm downloaded but will do it later. May have a troubleshooting section you can work through and post the results.
    My usual greeting is
    Welcome to the forum-
    We can help a lot more if you please post good clear pictures of the whole chassis, and then pictures of each board, front and back and close up of connectors, (max resolution 2000x2000 and 2MB) using the manage attachments button, which is found by clicking "go advanced" under quick reply.

    Please do not post inline and offsite as they slow down the loading of pages.

    Examples of what is needed
    https://www.badcaps.net/forum/attach...1&d=1290283049

    https://www.badcaps.net/forum/attach...7&d=1280167246

    It will be useful if you can say what the supposed fault was and a bit about yourself - skills tools etc.
    Please upload pictures using attachment function when ask for help on the repair
    http://www.badcaps.net/forum/showthread.php?t=39740

    Comment


      #3
      Re: 42lg3000-za No Picture but got sound

      Thanks selldoor, had to go get a decent multimeter, when you say pin1, pin2 where do i look for these points.

      Only thing i notice was i did a voltage check on the leads going to the inverter boards, they say 24.5v, the first 5 pins of that connecter (Both master & slave).

      I was told it has no picture, it does have sound. Plugged in an checked.
      About me im a real novice in electronics, hobbist.

      Comment


        #4
        Re: 42lg3000-za No Picture but got sound

        I was hoping you would have the Service manual to work off.
        There should be a connector to the main board list the voltages on that.
        Is it labelled
        Please upload pictures using attachment function when ask for help on the repair
        http://www.badcaps.net/forum/showthread.php?t=39740

        Comment


          #5
          Re: 42lg3000-za No Picture but got sound

          Like were it says output:

          5.2v - 6.5a
          12v - 2.25a
          16.5 - 1.3a
          24v - 7.5a

          Comment


            #6
            Re: 42lg3000-za No Picture but got sound

            did you get the schematic

            Or do you mean like p204 Got 14 pins,
            pin 1 is a blue wire should be 24v
            pin 2 is grey 24v
            pin 3 is grey 24v
            pin 4 is grey 24v
            pin 5 is grey 24v

            Then the next 6 to 10 are GND
            pin 11 =BR1
            pin 12 =on/off
            pin 13 =pwd dim
            pin 14 =error

            Does this make sense?
            Last edited by Jahson; 05-30-2012, 12:39 PM.

            Comment


              #7
              Re: 42lg3000-za No Picture but got sound

              No - I think that must be in the middle of the board somewhere - remember I have never seen one of these. It will be a connector on the edge somewhere if the boards are still on the chassis you may not see what the voltages are as the labels, may be on the underside (if there are any)

              No to schematic -no time to try- did you?
              Please upload pictures using attachment function when ask for help on the repair
              http://www.badcaps.net/forum/showthread.php?t=39740

              Comment


                #8
                Re: 42lg3000-za No Picture but got sound

                no label

                Comment


                  #9
                  Re: 42lg3000-za No Picture but got sound

                  Just to check - I dont mean a stuck on label I mean writing on the board silkscreened.
                  Not that it really matters - just start at one end and work along the pins- you might have to stick the redprobe in small holes along the side of the connector - it is sometimes quite difficult to get a connection
                  Please upload pictures using attachment function when ask for help on the repair
                  http://www.badcaps.net/forum/showthread.php?t=39740

                  Comment


                    #10
                    Re: 42lg3000-za No Picture but got sound

                    yea i did that, theres 3 connecters in total, 1 goes to master inverter, slave inverter, an the other to the av board if its called that the (board you connect scart, hmdi) this av connector slightly difference it has double row.

                    Comment


                      #11
                      Re: 42lg3000-za No Picture but got sound

                      that connection for av board

                      pin 1 should be 16.5 meter reads 15.6
                      pin 2 gnd
                      pin 3 should be 12 meter reads 12.3
                      pin 4 gnd
                      pin 5 should be 5 meter reads 5.1
                      pin 6 should be 5 meter reads 5.1
                      pin 7 gnd
                      pin 8 gnd
                      pin 9 ACD
                      pin 10 on/off meter reads 2.9
                      pin 11 pwm dim meter reads 0
                      pin 12 n.c meter reads 0

                      Comment


                        #12
                        Re: 42lg3000-za No Picture but got sound

                        selldoor does this make sense.
                        Dont know what i done but messed up my borrowed sealey mm20 meter.
                        tommorrow i have the pictures up, will be buying a camera.

                        Comment


                          #13
                          Re: 42lg3000-za No Picture but got sound

                          The voltages dont look too bad 16.5 is is a bit low.

                          Dont know what i done but messed up my borrowed sealey mm20 meter.
                          The battery may be low or youve blown the fuse - have you got insructions?
                          Available here:
                          Please upload pictures using attachment function when ask for help on the repair
                          http://www.badcaps.net/forum/showthread.php?t=39740

                          Comment


                            #14
                            Re: 42lg3000-za No Picture but got sound

                            With lights out in room does screen light up?

                            If so - T-con or main board, most likely T-con

                            If not - Inverter or PSU, most LG LCDs 42" and above integrate the inverter and PSU onto one board.
                            Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
                            For service manual, schematic, boardview (board view), datasheet, cad - use our search.

                            Comment


                              #15
                              Re: 42lg3000-za No Picture but got sound

                              hiya tom66 the meter is ok now many thanks yea i think it was the fuse.

                              With total darkness in room, cant see any lights on screen

                              Dont know if this helps but on start up the red standby light flashes 3 times?

                              I will mos def have a camera,and take some shots.

                              Comment


                                #16
                                Re: 42lg3000-za No Picture but got sound

                                Here the shots as promised
                                Attached Files

                                Comment


                                  #17
                                  Re: 42lg3000-za No Picture but got sound

                                  Too blurry to see anything really - does your camera have a macro mode?

                                  My 42LC46 flashes the LED a few times when first turned on, seems normal.

                                  I would suspect the inverter board.
                                  Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
                                  For service manual, schematic, boardview (board view), datasheet, cad - use our search.

                                  Comment


                                    #18
                                    Re: 42lg3000-za No Picture but got sound

                                    in pic 6 by the bottom white connector to the left of it theres a white fuse does that test ok?

                                    Comment


                                      #19
                                      Re: 42lg3000-za No Picture but got sound

                                      Same goes for Pic 5 White rectangle is probably a fuse.
                                      Test with meter on Ohms one probe to each side of fuse- should be the same as touching probes together.



                                      Probably need more light for photos - can you take outside for best natural light
                                      Last edited by selldoor; 06-02-2012, 10:36 AM. Reason: light
                                      Please upload pictures using attachment function when ask for help on the repair
                                      http://www.badcaps.net/forum/showthread.php?t=39740

                                      Comment


                                        #20
                                        Re: 42lg3000-za No Picture but got sound

                                        sorry for the blurry images, brought a real cheap camera and cant return it? unless its faulty.

                                        I think a soldering iron can fix that problem?

                                        Comment

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