Sharp LC-52LE830U no backlight

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  • 73buick
    Member
    • Mar 2011
    • 41
    • USA

    #1

    Sharp LC-52LE830U no backlight

    Getting the one long one short blink. If I do the force start, I get picture, but no backlight.

    With above and LED connector plugged in, meter on LED1-4+ starts at 40VDC (maybe higher, but that is after 5-10 seconds after the force start) and then slowly drops stays around .1VDC. LED1-4- show 0VDC.

    With unit off, ohm reading on LED1-4+ are about 2.7MOhms, LED1-4- around 1.9MOhms.

    LED connector unplugged, ohm readings off PSU board pins the same. Power reading, this time on LED1+ I caught it starting at about 120VDC, but again slowly was dropping.

    Bad PSU board? I should be getting steady high VDC (150-200 I assume) out of the LED+ pins from it with the LED connector off, right?
  • R_J
    Badcaps Legend
    • Jun 2012
    • 9535
    • Canada

    #2
    Re: Sharp LC-52LE830U no backlight

    The actual voltage depends on how many led's and there configuration. The led supply also detects if there is a problem and shuts down if it detects a fault.
    You need to have your probes on the +led then turn on the tv as the voltage will come up then drop if an error is detected.
    You can not check the led strings with a ohm meter. I would suspect you have one or more bad led's in the panel.
    Last edited by R_J; 07-21-2018, 09:36 PM.

    Comment

    • budm
      Badcaps Legend
      • Feb 2010
      • 40746
      • USA

      #3
      Re: Sharp LC-52LE830U no backlight

      How about the Voltage readings on the LED- (Cathode return) for each LED -? You will have to leave the probe on the pins while turning the TV ON.
      Pictures of the boards an what we are dealing with?
      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

      • 73buick
        Member
        • Mar 2011
        • 41
        • USA

        #4
        Re: Sharp LC-52LE830U no backlight

        Here is the board in question. Just did this test. Plugged in, lamp error flash. Meter on LED1+, 0VDC. Leaving probe on LED1+, did a force start. Meter stayed at 0VDC. Tried on LED2+ as well, same thing.
        Attached Files

        Comment

        • budm
          Badcaps Legend
          • Feb 2010
          • 40746
          • USA

          #5
          Re: Sharp LC-52LE830U no backlight

          "With above and LED connector plugged in, meter on LED1-4+ starts at 40VDC (maybe higher, but that is after 5-10 seconds after the force start) and then slowly drops stays around .1VDC." So you were getting 40V on the LED+ and now you are getting Zero?
          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

          • 73buick
            Member
            • Mar 2011
            • 41
            • USA

            #6
            Re: Sharp LC-52LE830U no backlight

            The first time I wasn't measuring right away. Not sure if that would make a difference. I am going to test again both ways to be sure.

            Comment

            • budm
              Badcaps Legend
              • Feb 2010
              • 40746
              • USA

              #7
              Re: Sharp LC-52LE830U no backlight

              You need to leave the probes in place before tuning on the TV, then you will watch the meter to see how high the Voltage jumps up to when the TV is turned on and how low it goes down to after 10 seconds.
              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

              • 73buick
                Member
                • Mar 2011
                • 41
                • USA

                #8
                Re: Sharp LC-52LE830U no backlight

                Okay, did it again. These readings are going from lamp error state to forced start up state. Probes are set on pins from the get go.

                LED1+: Takes 3-5 sec from the relay click to jump to 140VDC for a second, then starts dropping. After about 10 sec, its around 20-40 VDC and still dropping.
                LED2+: Same
                LED4+ Same

                LED1-: Again about 3-5 sec from the relacy click and jumps to about 70VDC for a second and starts dropping right after.
                LED4-: Same

                With LED connector off, +/- pins stay at 0VDC.

                Comment

                • 73buick
                  Member
                  • Mar 2011
                  • 41
                  • USA

                  #9
                  Re: Sharp LC-52LE830U no backlight

                  Bump. Bad LED?

                  Comment

                  • budm
                    Badcaps Legend
                    • Feb 2010
                    • 40746
                    • USA

                    #10
                    Re: Sharp LC-52LE830U no backlight

                    Originally posted by 73buick
                    Okay, did it again. These readings are going from lamp error state to forced start up state. Probes are set on pins from the get go.

                    LED1+: Takes 3-5 sec from the relay click to jump to 140VDC for a second, then starts dropping. After about 10 sec, its around 20-40 VDC and still dropping.
                    LED2+: Same
                    LED4+ Same

                    LED1-: Again about 3-5 sec from the relacy click and jumps to about 70VDC for a second and starts dropping right after.
                    LED4-: Same

                    With LED connector off, +/- pins stay at 0VDC.
                    You have four LED strings so what happen to LED2-, LED 3+, LED3-?
                    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

                    • 73buick
                      Member
                      • Mar 2011
                      • 41
                      • USA

                      #11
                      Re: Sharp LC-52LE830U no backlight

                      Sorry, same readings for the others, too.

                      Comment

                      • budm
                        Badcaps Legend
                        • Feb 2010
                        • 40746
                        • USA

                        #12
                        Re: Sharp LC-52LE830U no backlight

                        1) So to be clear, all four LED (-) Cathode return of the LED strings pins shows 70V after the relay clicks and then drops down right after. Correct? 70V reading on the Cathode return lines are high, typical value is around 20 ~30V range.
                        Need to do more investigation.
                        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

                        • 73buick
                          Member
                          • Mar 2011
                          • 41
                          • USA

                          #13
                          Re: Sharp LC-52LE830U no backlight

                          Okay, so I went and tested everything again. I had my intern doing it before and wanted to just do it myself. I did each test twice to confirm readings. So starting with TV unplugged and LED connector plugged in.

                          Plug in TV, lamp error flash and 0VDC on LED1-4 +/-.

                          Force power on: Relay clicks. LED1-4 +/- will jump about a tenth of volt for a second. After about 25-30 seconds, LED1-4 + jumps to 140VDC for a second, then relay clicks again, voltage drops by half and continues to drop and lamp error flash returns. LED1-4 - jumps to 70VDC for a second, and does the same thing.

                          One thing to note, when I first was testing this last week initially, before I had the back off, I could force power it on and it would stay on. It wouldn't click back to lamp error after 30 seconds.
                          Attached Files
                          Last edited by 73buick; 07-27-2018, 04:49 PM.

                          Comment

                          • 73buick
                            Member
                            • Mar 2011
                            • 41
                            • USA

                            #14
                            Re: Sharp LC-52LE830U no backlight

                            Bump. I have an LED tester on the way, too, just in case.

                            Comment

                            • 73buick
                              Member
                              • Mar 2011
                              • 41
                              • USA

                              #15
                              Re: Sharp LC-52LE830U no backlight

                              Okay, so I believe I confirmed bad LEDs. Using the LED tester, I unplugged the LED connector and tested LED1+/- through LED4+/-. LED1,3,4 are tested at around 70-72VDC and I could see areas of light brightening up on the screen. LED 2 at first went to around 85VDC, then after a few tests the tester just would drop from the default 327VDC to maybe 323VDC, a couple times would flucuate from 130 to 260 and back and forth, so I am assuming that LED string is bad.

                              Comment

                              • budm
                                Badcaps Legend
                                • Feb 2010
                                • 40746
                                • USA

                                #16
                                Re: Sharp LC-52LE830U no backlight

                                Yep.
                                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

                                • 73buick
                                  Member
                                  • Mar 2011
                                  • 41
                                  • USA

                                  #17
                                  Re: Sharp LC-52LE830U no backlight

                                  Okay, so I got the new LED strip in. Plug in, still on lamp error. Do force start and it turns on and lights up good. I can go into menu settings, etc, looks good. Unplug and plug in again, still on lamp error blinking. Force start, go into menu and do a reset. No change. Look up and see it probably needs to go into service mode to reset the lamp error code. Instructions I find online and in the service manual say to push Vol- and Input buttons on TV, then hit power and keep the first two pressed until I see the K icon show up. I have tried over a dozen times now, the K never shows up. The turns on, but no K icon. I tried once doing with TV unplugged first, but that just made it go back into error lamp mode. One thing I did notice is sometimes the touch buttons haven't been responding, but I don't know if that is just a normal thing if maybe the get touched too many times and it locks itself out for short time b/c when it does that, if I just wait 10-20 sec, then they work. I thought maybe I need to use the remote (I don't have it presently), but the service manual says to use the buttons on the tv.

                                  Comment

                                  • vinceroger69
                                    Badcaps Legend
                                    • Mar 2012
                                    • 6714
                                    • uk

                                    #18
                                    Re: Sharp LC-52LE830U no backlight

                                    have you retested the 4 led strips with your led tester what readings are you getting now

                                    Comment

                                    • 73buick
                                      Member
                                      • Mar 2011
                                      • 41
                                      • USA

                                      #19
                                      Re: Sharp LC-52LE830U no backlight

                                      All test same now, 70-72V using the LED powersupply/tester.

                                      Comment

                                      • budwich
                                        Badcaps Legend
                                        • Jul 2015
                                        • 3097
                                        • Canada

                                        #20
                                        Re: Sharp LC-52LE830U no backlight

                                        I think your issue is indeed, you have to get into the service menu to reset the counters. Your "words" on the process for getting there give me the impression that you are "hitting" the power button.... that's not what you have to do, you have plug into power while holding down the buttons that you indicated. That should get you there. Without resetting the error counters, your set will always be in "error" as a factory reset doesn't do anything for the counters.

                                        Comment

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