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LG 55LW5600 No Video No Sound

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    LG 55LW5600 No Video No Sound

    I'll start by saying I'm not much of a techy, but my TV is dead and thought I'd pull the thread of repairing it. So keep in mind my electronics knowledge is very limited.

    I've spent the last few days reading threads and doing research on what might be wrong with my TV. I did try a reflow (both heat gun and oven) of the main board based on a number of people with similar symptoms with no change.

    So there is no "standby light" on when the TV is just plugged in but off. I believe there used to be but I can't be 100% sure. When I turn the TV on (touch panel or remote) I get a "click", the power indicator lights up red, fades off, lights up red again, fades off, then lights up blue/white and stays on. No screen flashes and I can't see any signs of an image with a flashlight in a dark room. I get a "click" when I turn it off.

    I have a multimeter and checked P201 (power out from power board to main board) while the TV was on.

    L Column/R Column/Voltage(measured)
    N.C./Error
    12v/PWM/~12v
    12v/N.C./~12v
    12v/DRV-ON/~12v
    GRD/VSYNC_IN
    GRD/GRD
    3.5v/3.5v/~3.5v
    3.5v/3.5v/~3.5v
    GRD/GRD
    GRD/GRD
    24v/24v/~24v
    Power-On/24v/~3.3v

    Rather than hope that my symptoms where "close enough" to others and keep tinkering, I was hoping to get advice from the experts here. Any help is appreciated. I'll add pictures in a bit.

    #2
    Re: LG 55LW5600 No Video No Sound

    Can you post pictures of your boards and voltage measurements are easier to read if posted similar to the following.
    Without the set in front of us, the more information you can provide the better chance of finding a solution.
    Attached Files
    Last edited by dick_barton; 07-28-2018, 09:09 AM.
    Willing to help but I'm no expert.

    Comment


      #3
      Re: LG 55LW5600 No Video No Sound

      Originally posted by dick_barton View Post
      Can you post pictures of your boards and voltage measurements are easier to read if posted similar to the following.
      Without the set in front of us, the more information you can provide the better chance of finding a solution.
      I have attached some pictures of the set. In your example, are those readings on each end of the ribbon or what? I was a bit confused on what the tho columns meant. At any rate, the only that jumped out as odd to me was the last one. Labeled as 24v and I measured 3.3v.
      Attached Files
      Last edited by mtskibum16; 07-28-2018, 02:13 PM.

      Comment


        #4
        Re: LG 55LW5600 No Video No Sound

        The connector on the power supply board that goes to the main board has 24 pins.
        The exposed pins you can see from the top side of the board are the ODD number pin, if you look at the board you will see Black Triangle marking which indicates pin1 of the connector.
        To get to the EVEN number pins you have to use the skinny probes to probe the pins from the wire entrance side of the connector.
        L Column (ODD). R Column (EVEN)
        pin 23: N.C. pin 24: Error
        pin 21: 12v. pin 22: PWM (Dimming)
        pin 19: 12v. pin 20: N.C. (No Connection)
        pin 17: 12v. pin 18: DRV-ON (same as BL-ON)
        pin 15: GRD. pin 16: VSYNC_IN
        pin 13: GRD. pin 14: GRD
        pin 11: 3.5v. pin 12: 3.5v
        pin 9: 3.5v. pin 10: 3.5v
        pin 7: GRD. pin 8: GRD
        pin 5: GRD. pin 6: GRD
        pin 3: 24v. pin 4: 24v
        pin 1: Power-On. pin 2: 24v
        Last edited by budm; 07-28-2018, 03:10 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


          #5
          Re: LG 55LW5600 No Video No Sound

          Originally posted by budm View Post
          The connector on the power supply board that goes to the main board has 24 pins.
          The exposed pins you can see from the top side of the board are the ODD number pin, if you look at the board you will see Black Triangle marking which indicates pin1 of the connector.
          To get to the EVEN number pins you have to use the skinny probes to probe the pins from the wire entrance side of the connector.
          L Column (ODD). R Column (EVEN)
          pin 23: N.C. pin 24: Error
          pin 21: 12v. pin 22: PWM (Dimming)
          pin 19: 12v. pin 20: N.C. (No Connection)
          pin 17: 12v. pin 18: DRV-ON (same as BL-ON)
          pin 15: GRD. pin 16: VSYNC_IN
          pin 13: GRD. pin 14: GRD
          pin 11: 3.5v. pin 12: 3.5v
          pin 9: 3.5v. pin 10: 3.5v
          pin 7: GRD. pin 8: GRD
          pin 5: GRD. pin 6: GRD
          pin 3: 24v. pin 4: 24v
          pin 1: Power-On. pin 2: 24v
          Thank you for the info! SO on the wire entrance side, there are two rows of wires (so 24 total). Are the even pins the top or bottom row of wires? I hope that makes sense.

          Comment


            #6
            Re: LG 55LW5600 No Video No Sound

            Bottom.
            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


              #7
              Re: LG 55LW5600 No Video No Sound

              Originally posted by budm View Post
              Bottom.
              Originally posted by dick_barton View Post
              Can you post pictures of your boards and voltage measurements are easier to read if posted similar to the following.
              Without the set in front of us, the more information you can provide the better chance of finding a solution.
              This is the connector discussed above. Hopefully that means something to you guys.
              Attached Files

              Comment


                #8
                Re: LG 55LW5600 No Video No Sound

                DRV_ON is missing which I believe turn the backlights on and is controlled by the main board.
                On some sets if you disconnect the main board from the power supply and switch on, the backlights come on and stay on?
                Are you certain you have no picture. Keep pressing the menu button on the remote and check the screen carefully.
                Willing to help but I'm no expert.

                Comment


                  #9
                  Re: LG 55LW5600 No Video No Sound

                  I don't see the screen. Just got the room nice and dark and inspected again with a flashlight. I don't see anything.

                  I tried unplugging the main board and the TV doesn't turn on. I read somewhere about jumping certain pins (maybe with a resistor?) to get the backlights to come on.

                  So what is the most logical way to diagnose this? Is the no standby light and or the blinking red light in startup any indication of anything?

                  Comment


                    #10
                    Re: LG 55LW5600 No Video No Sound

                    You could try disconnecting the main board from the power supply and connect any of the 3.5V pins to DRV_ON pin at the power supply end using a 1K resistor and see if backlights come on and stay on.

                    You may also have to connect 3.5V to Power_On pin if the 12V & 24V are not present using a second 1K resistor.
                    Last edited by dick_barton; 07-29-2018, 10:47 AM.
                    Willing to help but I'm no expert.

                    Comment


                      #11
                      Re: LG 55LW5600 No Video No Sound

                      Have a read through this. Troubleshooting Page 53 onwards
                      Attached Files
                      Last edited by dick_barton; 07-29-2018, 10:57 AM.
                      Willing to help but I'm no expert.

                      Comment


                        #12
                        Re: LG 55LW5600 No Video No Sound

                        Ok I'll try that and read through the info. There are two connectors going from the power board to main board. Do I disconnect both or only the connection P201 I posted?
                        Last edited by mtskibum16; 07-29-2018, 11:30 AM.

                        Comment


                          #13
                          Re: LG 55LW5600 No Video No Sound

                          Ok, I jumped DVR-ON to 3.5v and Power-On to 3.5v. Plug the TV in to the wall and the back lights come on and stay on.

                          Comment


                            #14
                            Re: LG 55LW5600 No Video No Sound

                            It does look as though you have a mainboard fault with DRV_ON not switching. Can you post photo's of your main board.
                            Check the voltages on Q504 on the mainboard (Page 76)
                            Last edited by dick_barton; 07-29-2018, 12:43 PM.
                            Willing to help but I'm no expert.

                            Comment


                              #15
                              Re: LG 55LW5600 No Video No Sound

                              Originally posted by dick_barton View Post
                              It does look as though you have a mainboard fault with DRV_ON not switching. Can you post photo's of your main board.
                              Picture of the mainboard is pic 3 in post 3. I can get better pics of anything specific. Also page 71 of the link you posted has details on it. I'm working on reading through that.

                              I have attached the readings for Q504 with the TV off and TV on.
                              Attached Files
                              Last edited by mtskibum16; 07-29-2018, 01:26 PM.

                              Comment


                                #16
                                Re: LG 55LW5600 No Video No Sound

                                +3.3V_ Normal appears to be missing. Can you check what voltage is on pins 2, 6, 7 & 8 of IC505 (Page 73)
                                Willing to help but I'm no expert.

                                Comment


                                  #17
                                  Re: LG 55LW5600 No Video No Sound

                                  This is assuming counter clockwise around the component from pin 1 marked with the dot on page 74.
                                  Attached Files

                                  Comment


                                    #18
                                    Re: LG 55LW5600 No Video No Sound

                                    Originally posted by mtskibum16 View Post
                                    This is assuming counter clockwise around the component from pin 1 marked with the dot on page 74.
                                    Yes that is correct. It looks as either the IC has failed and is not giving out the +3.3V_Normal required to drive the backlights on via DRV_ON or since
                                    this supply goes to many other parts of the circuit as shown on Page 104, one part may be pulling this supply low.

                                    With the set powered off can you measure the resistance in ohms of IC505 pin 8 (+3.35V OUT) to pin 1 (GND)

                                    What is the part number written on top of the IC505
                                    Attached Files
                                    Last edited by dick_barton; 07-30-2018, 03:48 AM.
                                    Willing to help but I'm no expert.

                                    Comment


                                      #19
                                      Re: LG 55LW5600 No Video No Sound

                                      Plugged in (but off): 162.5 ohms
                                      Not plugged in: 12.3 ohms

                                      I'll have to bring an inspection glass home from work tomorrow for the part number. I can't make it out with the naked eye. My wife thinks it's as follows, but I'll verify tomorrow.

                                      Z1024DI
                                      ZA1012

                                      Comment


                                        #20
                                        Re: LG 55LW5600 No Video No Sound

                                        Originally posted by mtskibum16 View Post
                                        Plugged in (but off): 162.5 ohms
                                        Not plugged in: 12.3 ohms

                                        I'll have to bring an inspection glass home from work tomorrow for the part number. I can't make it out with the naked eye. My wife thinks it's as follows, but I'll verify tomorrow.

                                        Z1024DI
                                        ZA1012
                                        Is it 12 Ohms readings in both directions of the probes?
                                        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

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