LG 42LV5500 TV - black screen, no sound, no image, no backlight

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  • russianbot
    Member
    • Jan 2019
    • 11
    • USA
    #1

    LG 42LV5500 TV - black screen, no sound, no image, no backlight

    My LG TV 42LV5500 no longer shows anything on the screen. There is no backlight, no audio from external input sources, and using a flashlight I can't see anything on the screen either. When powering on, the status LED changes color and it makes a faint click as usual, but nothing else happens.

    The problem happened unexpectedly - everything worked ok until one day it just doesn't show anything when powering on. I took the back cover off, there's a green board (I'm guessing the main board) and a brown board (probably the power board). Don't see any bulging or leaking capacitors. I checked the 3 fuses on the power board, and they're ok.

    Any ideas what can be the problem? What else can I check to diagnose the problem?

    I uploaded photos of the two boards, and closeups of the power board.
    Attached Files
    Tags: None
    • budm
      Badcaps Legend
      • Feb 2010
      • 40746
      • USA
      #2
      Re: LG 42LV5500 TV - black screen, no sound, no image, no backlight

      The connector on the power supply board that goes to the Main board has pin name for each pin, you need to check the Voltage on each pin when TV is OFF and when power switch is activated.
      You MUST put down the pin name and follow by the Voltage reading for each pin so we can easily see what the Voltages are.
      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

        • CapLeaker
          Leaking Member
          • Dec 2014
          • 7973
          • Canada
          #3
          Re: LG 42LV5500 TV - black screen, no sound, no image, no backlight

          Adding to budm request, turn the TV on and measure the 450V main capacitor. Be careful working there!

            Comment

            • neilc6
              Badcaps Legend
              • Nov 2015
              • 1550
              • Canada
              #4
              Re: LG 42LV5500 TV - black screen, no sound, no image, no backlight

              LV series suffers from BGA failure.on the main processor

              https://ebay.us/NkMDFB

              Main board failures our service covers:
              TV can be turned on and off, however no back-light appears, no picture, or sound
              TV turns on but picture has strange lines all all inputs and on menus
              TV Turns on, LG logo appears on screen, but then does not show any picture
              TV Turns on, but freezes on the LG Logo
              HDMI Ports have no signal

                Comment

                • russianbot
                  Member
                  • Jan 2019
                  • 11
                  • USA
                  #5
                  Re: LG 42LV5500 TV - black screen, no sound, no image, no backlight

                  I measured the voltage across the 450V capacitors, they show about 400V when the TV is powered on.
                  Measured the voltages on the 24 pin connector from the power board to the main board. Here are the voltages listed below for each pin when the unit is in standby mode and when powered on. Some pins have a small AC voltage, so I listed those too.

                  Pin_____OFF_____ON
                  NC______0_______0____(0.6 - 1V AC 120Hz)
                  12V_____0_______11.89
                  12V_____0_______11.89
                  12V_____0_______11.89
                  GND_____0_______0
                  GND_____0_______0
                  3.5V____3.5_____3.5
                  3.5V____3.5_____3.5
                  GND_____0_______0
                  GND_____0_______0
                  24V_____0_______24.4
                  PWN-ON__0_______3.4
                  ERROR___0_______0
                  PWM_____0_______3.2
                  NC______0_______0____(0.6V - 1V AC 120Hz)
                  DRV-ON__0_______0.04
                  VSYNC___0_______0____(0.6V - 1V AC 120Hz)
                  GND_____0_______0
                  3.5V____3.5_____3.5
                  3.5V____3.5_____3.5
                  GND_____0_______0
                  GND_____0_______0
                  24V_____0_______24.4
                  24V_____0_______24.4



                  I might try reflowing the CPU on the main board with a heat gun, I heard some people fixed their TV that way.

                    Comment

                    • nomoresonys
                      Badcaps Legend
                      • Jan 2013
                      • 12079
                      • U.S.
                      #6
                      Re: LG 42LV5500 TV - black screen, no sound, no image, no backlight

                      Looks like you're not getting proper drv-on voltage from the mainboard.

                        Comment

                        • nomoresonys
                          Badcaps Legend
                          • Jan 2013
                          • 12079
                          • U.S.
                          #7
                          Re: LG 42LV5500 TV - black screen, no sound, no image, no backlight

                          Try unplug cable from powerboard to mainboard, plug tv back into outlet turn on tv, see if backlights come on and stay on.

                            Comment

                            • CapLeaker
                              Leaking Member
                              • Dec 2014
                              • 7973
                              • Canada
                              #8
                              Re: LG 42LV5500 TV - black screen, no sound, no image, no backlight

                              your main board isn't sending DRV-ON signal (back lights).

                                Comment

                                • neilc6
                                  Badcaps Legend
                                  • Nov 2015
                                  • 1550
                                  • Canada
                                  #9
                                  Re: LG 42LV5500 TV - black screen, no sound, no image, no backlight

                                  Originally posted by nomoresonys
                                  Try unplug cable from powerboard to mainboard, plug tv back into outlet turn on tv, see if backlights come on and stay on.
                                  I believe this test only works with Samsungs. LGs dont have pullup resistors.

                                    Comment

                                    • CapLeaker
                                      Leaking Member
                                      • Dec 2014
                                      • 7973
                                      • Canada
                                      #10
                                      Re: LG 42LV5500 TV - black screen, no sound, no image, no backlight

                                      then force the psu on. Unhook the main board from the PSU. Put a 1k resistor from STBY to PSon and another resistor from STBY to BLon.

                                        Comment

                                        • nomoresonys
                                          Badcaps Legend
                                          • Jan 2013
                                          • 12079
                                          • U.S.
                                          #11
                                          Re: LG 42LV5500 TV - black screen, no sound, no image, no backlight

                                          Yep, do what CapLeaker said, make sure cable from powerboard to mainboard is UNPLUGGED during test.
                                          Last edited by nomoresonys; 03-09-2019, 04:06 PM.

                                            Comment

                                            • nomoresonys
                                              Badcaps Legend
                                              • Jan 2013
                                              • 12079
                                              • U.S.
                                              #12
                                              Re: LG 42LV5500 TV - black screen, no sound, no image, no backlight

                                              Originally posted by neilc6
                                              I believe this test only works with Samsungs. LGs dont have pullup resistors.
                                              Works with any tv with pullup resistors. Didn't check this exact model, quick test, no results then force on per CapLeaker's instructions.

                                                Comment

                                                • russianbot
                                                  Member
                                                  • Jan 2019
                                                  • 11
                                                  • USA
                                                  #13
                                                  Re: LG 42LV5500 TV - black screen, no sound, no image, no backlight

                                                  Good news - I reflowed the processor on the main board, and the TV works as good as new. Thanks for everyone's help and advice.

                                                    Comment

                                                    • neilc6
                                                      Badcaps Legend
                                                      • Nov 2015
                                                      • 1550
                                                      • Canada
                                                      #14
                                                      Re: LG 42LV5500 TV - black screen, no sound, no image, no backlight

                                                      Results may only be temporary and board will likely fail in weeks or months. Reballing is the proper repair.

                                                        Comment

                                                        • snme
                                                          Member
                                                          • Feb 2016
                                                          • 26
                                                          • AU
                                                          #15
                                                          Re: LG 42LV5500 TV - black screen, no sound, no image, no backlight

                                                          I also have a LG 42LV5500-TA, failed whilst in operation.
                                                          AC on relay click, nothing more.
                                                          Test of backlight was ok.
                                                          Test of RBGW rotation by T-Con was ok.
                                                          So now trying to find a mainboard EBU61302301, EAX64104703 (1) without much joy.
                                                          I'm guessing from prior comments that a hair drier fan on the video processor might not be ample heat for reflow. Perhaps longer localized time?
                                                          I am in Australia Sydney.
                                                          Last edited by snme; 08-25-2023, 09:34 PM. Reason: More particularly Sydney

                                                            Comment

                                                            • nomoresonys
                                                              Badcaps Legend
                                                              • Jan 2013
                                                              • 12079
                                                              • U.S.
                                                              #16
                                                              Re: LG 42LV5500 TV - black screen, no sound, no image, no backlight

                                                              Do test in post #10.

                                                                Comment

                                                                • snme
                                                                  Member
                                                                  • Feb 2016
                                                                  • 26
                                                                  • AU
                                                                  #17
                                                                  Re: LG 42LV5500 TV - black screen, no sound, no image, no backlight

                                                                  Yes I have done that backlight test, also T-Con RGBW pattern test.
                                                                  Both good.
                                                                  To clarify, above tests were conducted after finding INV-ON = DRV-ON was low from mainboard.
                                                                  Last edited by snme; 08-26-2023, 06:07 PM. Reason: Clarification

                                                                    Comment

                                                                    • nomoresonys
                                                                      Badcaps Legend
                                                                      • Jan 2013
                                                                      • 12079
                                                                      • U.S.
                                                                      #18
                                                                      Re: LG 42LV5500 TV - black screen, no sound, no image, no backlight

                                                                      Ok, well sure looks like the same issue as the op had, check out the diy reflows on youtube, need to be careful with the temps, use flux, at least look at a few, a lot of the posters know what they are doing and some don't.
                                                                      Last edited by nomoresonys; 08-27-2023, 10:19 AM.

                                                                        Comment

                                                                        • nomoresonys
                                                                          Badcaps Legend
                                                                          • Jan 2013
                                                                          • 12079
                                                                          • U.S.
                                                                          #19
                                                                          Re: LG 42LV5500 TV - black screen, no sound, no image, no backlight

                                                                          here is a very smart young man doing one on his tv, note how he suggests the fan at the end: https://www.youtube.com/watch?v=O1XGwQszLrc

                                                                            Comment

                                                                            • diif
                                                                              Badcaps Legend
                                                                              • Feb 2014
                                                                              • 6978
                                                                              • England
                                                                              #20
                                                                              Re: LG 42LV5500 TV - black screen, no sound, no image, no backlight

                                                                              The last LV series LG is reflowed I did over 2 years ago and its still going well.
                                                                              Anything you want to know about reflowing just ask.

                                                                                Comment

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