LG 47LS4500 not powering on, has standby light

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  • AcGeorgiegirl
    Badcaps Veteran
    • Jun 2013
    • 202
    • USA

    #1

    LG 47LS4500 not powering on, has standby light

    I'd posted(another posting) about this tv, but then everything changed, so I'm starting another thread, if that's ok. First, here's what was previously wrong:

    It was powering on, with sound and backlight- no picture, no menu shown, no matter what input was chosen. Sound worked on whatever input I tried.
    I tested the t-con's smd fuse, got 11.85 v on each lead. The P201 connecting power board to logic board has all 3 12-volts present, as well as all other voltages correct except the "Pwr-On", which I couldn't get a reading of(was at 0). I assumed one of the 12v pins supplied power to the t-con, going through the Logic board. I'd disconnected each of the panel ribbons, one at a time, and found that when the right ribbon was disconnected, I got half-screen of black with colored lines dispersed unevenly. When I disconnected the other side, the entire screen was glowing as before, when BOTH ribbons are connected.

    So...now this has all changed, and it no longer powers on. It does have a standby light(steady red). When I try turning it on, the standby light blinks 3 times slowly, stays off a couple of seconds, then goes back to steady red.
    Testing the P201 again, I find that no voltages are present except the 2 3.5v's.
    *I did cause a spark once, while testing the P201 the first go-round, and I'm worried I may have caused the set to now be shorted, or something, and not power up. The spark happened because I crossed more than one pin at the same time, I believe.
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  • CapLeaker
    Leaking Member
    • Dec 2014
    • 8133
    • Canada

    #2
    Re: LG 47LS4500 not powering on, has standby light

    Follow the 3.5V rail from the connector back on the PSU, though J96 back to the diode D201 and check it.
    Last edited by CapLeaker; 10-02-2016, 04:16 PM.

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    • AcGeorgiegirl
      Badcaps Veteran
      • Jun 2013
      • 202
      • USA

      #3
      Re: LG 47LS4500 not powering on, has standby light

      Originally posted by CapLeaker
      Follow the 3.5V rail from the connector back on the PSU, though J96 back to the diode D201 and check it.
      I'm not sure what you mean, sorry....are you saying to basically test the D201 diode?..or is there something else along the "way"?

      Comment

      • AcGeorgiegirl
        Badcaps Veteran
        • Jun 2013
        • 202
        • USA

        #4
        Re: LG 47LS4500 not powering on, has standby light

        D201 is reading 184 in diode mode.

        Comment

        • CapLeaker
          Leaking Member
          • Dec 2014
          • 8133
          • Canada

          #5
          Re: LG 47LS4500 not powering on, has standby light

          test that diode both ways. Check fuse F501, D510, D502, ZD503, ZD501 D501 (primary of the STBY voltage rail). That 3.5V rail should be always on, as it is your STBY voltage rail. No STBY voltage and your TV is dead as a nit, since it feeds the main board.

          The secondary side of the 3.5V rail really only has a that diode, an inductor and a capacitor and a few jumpers. So if that diode is good, the problem has to be on the primary section. So then we make sure these diodes I mentioned are good, the fuse is good and IC501 is getting power. If you still didn't find anything bad, I'd be replacing IC501.

          Hope that it isn't too complicated to follow.
          Last edited by CapLeaker; 10-02-2016, 05:16 PM.

          Comment

          • johnboy1313
            Badcaps Legend
            • Nov 2012
            • 1959
            • USA

            #6
            Re: LG 47LS4500 not powering on, has standby light

            https://www.badcaps.net/forum/showthread.php?t=44945

            Comment

            • AcGeorgiegirl
              Badcaps Veteran
              • Jun 2013
              • 202
              • USA

              #7
              Re: LG 47LS4500 not powering on, has standby light

              Originally posted by CapLeaker
              test that diode both ways. Check fuse F501, D510, D502, ZD503, ZD501 D501 (primary of the STBY voltage rail). That 3.5V rail should be always on, as it is your STBY voltage rail. No STBY voltage and your TV is dead as a nit, since it feeds the main board.

              The secondary side of the 3.5V rail really only has a that diode, an inductor and a capacitor and a few jumpers. So if that diode is good, the problem has to be on the primary section. So then we make sure these diodes I mentioned are good, the fuse is good and IC501 is getting power. If you still didn't find anything bad, I'd be replacing IC501.

              Hope that it isn't too complicated to follow.
              Thank you, CapLeaker...I think I've "got" what you are saying...helps to understand the primary/secondary thingy. I'm going to do a little reading so I understand better, then get started in the morning. I'll let you know!

              Comment

              • AcGeorgiegirl
                Badcaps Veteran
                • Jun 2013
                • 202
                • USA

                #8
                Re: LG 47LS4500 not powering on, has standby light

                Excellent "match", it seems, for my tv's issue. Thanks!

                Comment

                • CapLeaker
                  Leaking Member
                  • Dec 2014
                  • 8133
                  • Canada

                  #9
                  Re: LG 47LS4500 not powering on, has standby light

                  Pretty easy. You just follow everything backwards on the board until you hit power. Just remember for voltage measurements on the primary side, the ground reference point of your DMM (negative lead) is the negative leg of the main filter capacitor (not chassis GND!). As for the ground reference point for the secondary, that is chassis GND or any GND point on the secondary side. Good luck!

                  Comment

                  • AcGeorgiegirl
                    Badcaps Veteran
                    • Jun 2013
                    • 202
                    • USA

                    #10
                    Re: LG 47LS4500 not powering on, has standby light

                    All the diodes are good(all have OL on reverse polarity)
                    D501- 506
                    D502- 510
                    D510- 510
                    ZD503- 694
                    ZD501- 684

                    The F501 fuse is good, as well as the other 2 fuses on the primary.

                    Comment

                    • AcGeorgiegirl
                      Badcaps Veteran
                      • Jun 2013
                      • 202
                      • USA

                      #11
                      Re: LG 47LS4500 not powering on, has standby light

                      Well, I went ahead and also tested the rest of the diodes on the primary side, and found that D607 is shorted. Kudos to JohnnyBoy13...after all! CapLeaker, what do you think...should I try other tests to make sure the IC is ok, or can that even be done? I've never attempted that before. I've just replaced ic's as you've indicated, when the diodes and fuses all are good.

                      Comment

                      • AcGeorgiegirl
                        Badcaps Veteran
                        • Jun 2013
                        • 202
                        • USA

                        #12
                        Re: LG 47LS4500 not powering on, has standby light

                        Originally posted by AcGeorgiegirl
                        Well, I went ahead and also tested the rest of the diodes on the primary side, and found that D607 is shorted. Kudos to JohnnyBoy13...after all! CapLeaker, what do you think...should I try other tests to make sure the IC is ok, or can that even be done? I've never attempted that before. I've just replaced ic's as you've indicated, when the diodes and fuses all are good.
                        My DMM was low battery, so I replaced it and retested everything. The D607 isn't shorted
                        ....so I'm back to replacing the IC, I suppose. Is there any testing to be done to make sure it's ONLY the IC? I've checked all of the board's diodes, fuses, and what I recognize as transistors.

                        Comment

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