LG 47inch TV turns on but backlight shuts off quickly

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  • Lithium_Tonic
    New Member
    • Jul 2014
    • 3
    • US
    #1

    LG 47inch TV turns on but backlight shuts off quickly

    Hey Everyone,

    I have an LG 47ls4500 and had an issue come up in the last couple days.

    When I turn it on it appears perfect. Nice and bright normal good picture but then after about 3-4 seconds the backlight just turns off. I can see that the screen has video on it but it's to dim to make anything out. The TV operates perfectly normal just no backlight. I tried turning it off and back on several times and it consistently does the same exact thing.

    I know there is three boards in the back. The power supply/LED board (which I checked for bad caps and they all looked fine), the main board and the T-Con board.

    From what I've read this can likely be fixed relatively cheap but my biggest concern is which board is the actual problem.

    I appreciate any help on this.

    Thanks,

    Steve
    Tags: None
    • mann935
      New Member
      • Feb 2013
      • 3
      • Canada
      #2
      Re: LG 47inch TV turns on but backlight shuts off quickly

      This is a led tv and by the details you have given it seems you have a pic. but it is dim,if that is the case ,on menu pressing is it ok?

        Comment

        • Lithium_Tonic
          New Member
          • Jul 2014
          • 3
          • US
          #3
          Re: LG 47inch TV turns on but backlight shuts off quickly

          Originally posted by mann935
          This is a led tv and by the details you have given it seems you have a pic. but it is dim,if that is the case ,on menu pressing is it ok?
          Hey thanks for the response. When I press the menu button I can see that the menu comes up, however the backlight is still off. If I shine a flash light at it I can see that there is a picture.

            Comment

            • budm
              Badcaps Legend
              • Feb 2010
              • 40746
              • USA
              #4
              Re: LG 47inch TV turns on but backlight shuts off quickly

              How about posting good clear and well focused pictures of the back of the TV and also straight shot pictures of each boards?
              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

                • geminidpr
                  Member
                  • Dec 2011
                  • 41
                  #5
                  Re: LG 47inch TV turns on but backlight shuts off quickly

                  Hi Guys. I'm having the exact same problem with the exact same model (LG 47LS4500). It turns on and looks and sounds great for just a few seconds then the backlight goes off but sound stays on. I put a flashlight to it and I can see video so definitely a backlight problem.

                  The power supply has an LED that is blinking 4 times. I believe this is an error code but I don't know the error codes for this model. Does anyone have the error codes for this TV?

                  Thanx.
                  Attached Files

                    Comment

                    • budm
                      Badcaps Legend
                      • Feb 2010
                      • 40746
                      • USA
                      #6
                      Re: LG 47inch TV turns on but backlight shuts off quickly

                      We need to find out if the BL-ON (DRV-ON) signal to keep the backlights on is still present when the backlights drop out, so you need to check DCV on connector P201 DRV-ON to see if it has >2.5VDC at that pin when TV is on and when the backlights drops out.
                      This TV has 12 LED strings controlled by 12 circuits. You will have to check the DCV of each pin of the LED connectors P202, P203. You MUST provide the pin names and follow by the DCV reading for EACH pin.
                      Lg eay62512701 (eax64310401).
                      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

                        • Diah
                          Badcaps Legend
                          • Feb 2013
                          • 6343
                          • Germany
                          #7
                          Re: LG 47inch TV turns on but backlight shuts off quickly

                          Originally posted by geminidpr
                          Hi Guys. I'm having the exact same problem with the exact same model (LG 47LS4500). It turns on and looks and sounds great for just a few seconds then the backlight goes off but sound stays on. I put a flashlight to it and I can see video so definitely a backlight problem.

                          The power supply has an LED that is blinking 4 times. I believe this is an error code but I don't know the error codes for this model. Does anyone have the error codes for this TV?

                          Thanx.
                          this PWB even if you disconnect the LED plugs the green indicator will turn on flashing . also its possible you have bad soldering ... if there no bad soldering then you have one shorted edge LED
                          Last edited by Diah; 09-15-2016, 02:25 PM.

                            Comment

                            • geminidpr
                              Member
                              • Dec 2011
                              • 41
                              #8
                              Re: LG 47inch TV turns on but backlight shuts off quickly

                              Drv-on is at 3.3v when BL comes on and stays exactly the same when BL goes off.

                              LED + (P210) is at 36v when power is switched on and when BL comes on it goes to 56v then drops slightly to 53v when BL goes off.

                              Connectors P201 and P202 voltages are all at 7v when BL is on but jumps to 18-19v when the BL goes off.

                                Comment

                                • geminidpr
                                  Member
                                  • Dec 2011
                                  • 41
                                  #9
                                  Re: LG 47inch TV turns on but backlight shuts off quickly

                                  Originally posted by Diah
                                  this PWB even if you disconnect the LED plugs the green indicator will turn on flashing . also its possible you have bad soldering ... if there no bad soldering then you have one shorted edge LED
                                  Thanx Diah. I resoldered any suspicious connections and replaced main filter and C263 (100uf at 150 volts) and still the same so maybe it is LED array.

                                    Comment

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