LG 50LN5750 bad back light and odd question.

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  • freakaftr8
    Badcaps Legend
    • Oct 2012
    • 3743
    • USA

    #1

    LG 50LN5750 bad back light and odd question.

    I got this TV in for repair last night. Typical shorted LED strip. Got the back lights up and running and noticed I have no control over backlight control on the menus. It stays just as bright no matter what I do. Also APS power save mode does not seem to do anything. This obviously is either a firmware issue or the power supply simply does not control PWM dimming.

    So I am going to do it manually by stepping up the resistor value. My question is has anyone run into an issue where you cannot control backlight dimming on one of these LG's yet?
    Did I leave the soldering iron on?
  • Andrew F. Ali
    Badcaps Legend
    • Jan 2014
    • 2450
    • Trinidad & Tobago

    #2
    Re: LG 50LN5750 bad back light and odd question.

    LGs normally have a 'backlight' control in the User menu. If this does not control the backlights then yes stepping up the resistor value is the only option available. I have a R-C Substitution box that I use for that purpose. It will work out. Go brave.

    Comment

    • freakaftr8
      Badcaps Legend
      • Oct 2012
      • 3743
      • USA

      #3
      Re: LG 50LN5750 bad back light and odd question.

      I'm just surprised the backlight control and the power save APS mode doesn't work..
      Did I leave the soldering iron on?

      Comment

      • neilc6
        Badcaps Legend
        • Nov 2015
        • 1550
        • Canada

        #4
        Re: LG 50LN5750 bad back light and odd question.

        User manual says there is backlight control http://www.lg.com/ca_en/support/supp...ct/lg-50LN5750

        Comment

        • britishbloke
          New Member
          • Oct 2011
          • 5

          #5
          Re: LG 50LN5750 bad back light and odd question.

          Could the TV be in store demo mode?

          Comment

          • Andrew F. Ali
            Badcaps Legend
            • Jan 2014
            • 2450
            • Trinidad & Tobago

            #6
            Re: LG 50LN5750 bad back light and odd question.

            'I have no control over backlight control on the menus'.
            Do you mean the backlight control is greyed out or is there no adjuster control showing?
            Could really be in DEMO Mode as britishbloke suggests. However, I doubt it. Could you get to do a factory reset?

            Comment

            • freakaftr8
              Badcaps Legend
              • Oct 2012
              • 3743
              • USA

              #7
              Re: LG 50LN5750 bad back light and odd question.

              No the backlight control is there is just not doing anything. However problem solved. I guess that you have to have it connected to an input in order to see the effects of the backlight control.

              Shady.
              Did I leave the soldering iron on?

              Comment

              • Andrew F. Ali
                Badcaps Legend
                • Jan 2014
                • 2450
                • Trinidad & Tobago

                #8
                Re: LG 50LN5750 bad back light and odd question.

                You got me there, Pardner......Glad you figured out the problem......Problem was the User...hee...hee...hee

                Comment

                • freakaftr8
                  Badcaps Legend
                  • Oct 2012
                  • 3743
                  • USA

                  #9
                  Re: LG 50LN5750 bad back light and odd question.

                  Yes stupid me lol however on the fault of LG's part, Backlights at full luminance no matter where you have it adjusted on the menus When there is no signal fed to the television
                  Did I leave the soldering iron on?

                  Comment

                  • Andrew F. Ali
                    Badcaps Legend
                    • Jan 2014
                    • 2450
                    • Trinidad & Tobago

                    #10
                    Re: LG 50LN5750 bad back light and odd question.

                    I think you may have to adjust the backlight separately for each input, as the setting for HDMI is not the same setting for Video or TV, etc.

                    Comment

                    • budm
                      Badcaps Legend
                      • Feb 2010
                      • 40746
                      • USA

                      #11
                      Re: LG 50LN5750 bad back light and odd question.

                      Originally posted by Andrew F. Ali
                      I think you may have to adjust the backlight separately for each input, as the setting for HDMI is not the same setting for Video or TV, etc.
                      +1. I have to do that on my LG and SAMSUNG.
                      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

                      • freakaftr8
                        Badcaps Legend
                        • Oct 2012
                        • 3743
                        • USA

                        #12
                        Re: LG 50LN5750 bad back light and odd question.

                        Right, Im aware of backlight adjustments in each input including the common adjustment to add values to all ports.

                        However with the backlights adjusted down to 60% which is about as far as I'm willing to take these LG's, If I disconnect the H DMI cable or disconnect a component cable or whatever input I'm on, The backlights will go back to full luminance Until the source is connected again.
                        Did I leave the soldering iron on?

                        Comment

                        • budm
                          Badcaps Legend
                          • Feb 2010
                          • 40746
                          • USA

                          #13
                          Re: LG 50LN5750 bad back light and odd question.

                          Hmm, I will try that with my LG tonight.
                          42" LG in my bed room is at 35, 47" for the living room is at 50 and both are still pretty bright to me.
                          BTW, you said it goes to full when input is removed so the Backlights indicator bar goes to 100?
                          Last edited by budm; 01-18-2018, 03:02 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

                          • freakaftr8
                            Badcaps Legend
                            • Oct 2012
                            • 3743
                            • USA

                            #14
                            Re: LG 50LN5750 bad back light and odd question.

                            No indicator bar stays at where I have it set, just luminance maxes out
                            Did I leave the soldering iron on?

                            Comment

                            • budm
                              Badcaps Legend
                              • Feb 2010
                              • 40746
                              • USA

                              #15
                              Re: LG 50LN5750 bad back light and odd question.

                              But luminance is not the same as the Backlights.
                              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

                              • freakaftr8
                                Badcaps Legend
                                • Oct 2012
                                • 3743
                                • USA

                                #16
                                Re: LG 50LN5750 bad back light and odd question.

                                Ok I meant backlight level.
                                Did I leave the soldering iron on?

                                Comment

                                • arenat
                                  Member
                                  • Nov 2015
                                  • 22
                                  • Argentina

                                  #17
                                  Re: LG 50LN5750 bad back light and odd question.

                                  I´ve had that issue several times with LGs . No control no matter what , some work after factory reset , some don´t . It´s a software issue . Two identical 32LB560B , one work fine , control with no signal at all , the other like the OP´s.

                                  Comment

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