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RCA LED65G55R120Q No Backlight

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    RCA LED65G55R120Q No Backlight

    hello, I picked this TV up for free and started to diagnose it. I assume either a main board issue or shorted LED's. When I power it on, my voltages come up correctly and the LED's light for a split second. Then the entire system shuts down. No voltage anywhere. I assume shorted LED's forcing the PSU into protect so I disconnected the LED connector, powered on again, and the same issue occurred. Voltages came up for a second and then everything shut down. Any ideas?
    You Can't Succeed Until You're Willing to Fail

    #2
    Re: RCA LED65G55R120Q No Backlight

    Try disconnect powerboard from mainboard, turn it on see if backlight come on and stay on, always good practice to have tv unplugged from wall outlet before unplug any connector then plug tv in and try.

    Comment


      #3
      Re: RCA LED65G55R120Q No Backlight

      Pictures of what we are dealing with will help.
      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


        #4
        Re: RCA LED65G55R120Q No Backlight

        Originally posted by budm View Post
        Pictures of what we are dealing with will help.
        What connection should I remove on the main board?
        Attached Files
        You Can't Succeed Until You're Willing to Fail

        Comment


          #5
          Re: RCA LED65G55R120Q No Backlight

          "When I power it on, my voltages come up correctly and the LED's light for a split second."
          So what DC Voltages do you have on the control pins of the power supply board connector CN2: ADJ, BK, and PS?
          What Voltages do you have on the LED connector pins with LED connector in place? You need to leave the probe on each pin and then Turn on the TV to see how high it goes up to then wait 5 seconds to see how low it goes down to, do that on each pin of the LED connector, black probe on the chassis GND, you have two LED (+) and two LED (-) so 4 tests total.
          Last edited by budm; 01-23-2019, 11:34 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


            #6
            Re: RCA LED65G55R120Q No Backlight

            Voltage checks are a must as budm has indicated. A year ago I had set from friend of friend with similar problem except logo displayed. Power board and LEDs checked out OK by forcing them on. That left me with likely eeprom corrupted on main board. That set 65" Polaroid similar to RCA was recently given to me and I will first be trying freeze spray on the eeprom.

            Comment


              #7
              Re: RCA LED65G55R120Q No Backlight

              Originally posted by budm View Post
              "When I power it on, my voltages come up correctly and the LED's light for a split second."
              So what DC Voltages do you have on the control pins of the power supply board connector CN2: ADJ, BK, and PS?
              What Voltages do you have on the LED connector pins with LED connector in place? You need to leave the probe on each pin and then Turn on the TV to see how high it goes up to then wait 5 seconds to see how low it goes down to, do that on each pin of the LED connector, black probe on the chassis GND, you have two LED (+) and two LED (-) so 4 tests total.
              Sorry for the delay. I'm in WI and its been a rough week! Finally got voltages for you.

              PS-5Vs: 5.1v always

              ADJ-BK: 1.6v when turned on, drops to 0

              5V+5V: 4.9v once powered on, then drops to 0

              LED Connector (left to right)
              +: 285V drops to 0 in five seconds
              -: no reading

              +: 135V drops to 0 in 5 seconds
              -: no reading
              Last edited by zacheriaj; 01-30-2019, 04:59 PM.
              You Can't Succeed Until You're Willing to Fail

              Comment


                #8
                Re: RCA LED65G55R120Q No Backlight

                This is the typical Backlight failure issue.

                Comment


                  #9
                  Re: RCA LED65G55R120Q No Backlight

                  Originally posted by Andrew F. Ali View Post
                  This is the typical Backlight failure issue.
                  I assume the low voltage string is bad?
                  You Can't Succeed Until You're Willing to Fail

                  Comment


                    #10
                    Re: RCA LED65G55R120Q No Backlight

                    The higher voltage string is showing the same symptom. By displaying 0V on the both (-) pins say the Backlights are faulty and if you want to fix it then you would have to open up the Panel and test the Backlight Strings.

                    Comment


                      #11
                      Re: RCA LED65G55R120Q No Backlight

                      Originally posted by zacheriaj View Post
                      Sorry for the delay. I'm in WI and its been a rough week! Finally got voltages for you.

                      PS-5Vs: 5.1v always

                      ADJ-BK: 1.6v when turned on, drops to 0

                      5V+5V: 4.9v once powered on, then drops to 0

                      LED Connector (left to right)
                      +: 285V drops to 0 in five seconds
                      -: no reading

                      +: 135V drops to 0 in 5 seconds
                      -: no reading
                      You count the pins wrong for the connector CN2. It has 18 pins total. The expose pins you see from the top side of the board are ODD number pins, the even number pin you will have probe from the bottom side of the board or via the wire entrance side of the connector.
                      Pin name assignment for example: Pin 17 is ADJ (DIM control), Pin 18 is BK (BL-ON).
                      1) So to troubleshoot the problem we will need correct data first.
                      2) I need the pictures of the bottom side of the power supply board to see if the two LED strings are connected in series or not.
                      This looks to be the same as your board:
                      https://www.shopjimmy.com/rca-re46hq...led-board.htm#
                      RCA RE46HQ2120 Power Supply / LED Board
                      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


                        #12
                        Re: RCA LED65G55R120Q No Backlight

                        Hi, Any chance someone could post some high resolution pictures of the solder side of the power supply RE46HQ2120.
                        Thanks

                        Comment

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