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LG 42LN5700 issue

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    #1

    LG 42LN5700 issue

    Hello all, Just replaced all the LED strips in this set, during diagnostics I shorted out the power supply by arcing it against the chassis, so changed that too, the main board was missing one of the HDMI input connectors, so I changed that as well, I know, I know, should have just bought another set, this thing cost me $599 bucks, so I think it was personal. LOL, cost me around 120 for everything Iv'e done so far, But my issue is this. I have two wide strips of a yellow or bright hue going vertically on either side of the center, it's like racing strips if you will, it is so faint I'm not sure i can even get a picture of it to post, I was thinking the obvious t-con board, but could also be the LVDS cable, and other causes you can think of? would a bad panel cause this? when the led went out it literally seemed like it blew up with significant burning on the strip itself as well as the plastic strip cover, it also has burn marks. didn't know they could do that.
    Attached Files
    39 Soldering Iron burns And Counting
    Tags: None
    #2
    Re: LG 42LN5700 issue

    That is minor, I have seen them burn up the white plastic sheet in side the panel. I have also seen a samsung led strip short and shut down the power supply (but the power supply was ok)
    Check the cables between the panel and the t-con and make sure there is not a damaged conductor on the flat cable.
    But in this case I suspect you may have damaged the tab connection to the panel. Either the thin flex cable is bad or the cof ic is bad,

    Comment

      #3
      Re: LG 42LN5700 issue

      I was super careful with those tabs, I'll recheck the connections at the tcon and see what I get out of it, not sure how to repair bonded ic's
      39 Soldering Iron burns And Counting

      Comment

        #4
        Re: LG 42LN5700 issue PICS

        managed to get some pictures of it.
        Attached Files
        39 Soldering Iron burns And Counting

        Comment

          #5
          Re: LG 42LN5700 issue

          That does'nt look like a tab issue, it looks more like a diffuser issue, Are you sure you installed them back the same way?
          If it was a tab or driver issue, the edges of the bands would be sharply defined.
          Have you tried your original main board to see if it changes anything?
          Last edited by R_J; 02-12-2020, 11:25 AM.

          Comment

            #6
            Re: LG 42LN5700 issue

            have not tried original main board, will do that and reply. thank you I leaned everything against the wall behind the set when I replaced the led strips, stacking in order against the wall i should say, Making it nearly impossible to arrange diffusers in any sort of incorrect order. Kind of wondering if the back being off and some of the holes in the metal frame letting light escape in certain area's, anything like that sound possible? just spit balling here. LOL
            Last edited by LITEZONER; 02-12-2020, 11:48 AM.
            39 Soldering Iron burns And Counting

            Comment

              #7
              Re: LG 42LN5700 issue

              The obvious question here is are your strips mounted vertically and if so does the colour shift line up with where the strips are ?

              Also were there any plastic spacers under the screen and were they replaced ?
              Last edited by mmartell; 02-13-2020, 04:26 AM.

              Comment

                #8
                Re: LG 42LN5700 issue

                no spacers in there, strips mount horizontally and are staggered from strip to strip which I found odd, the others Iv'e done all the led's lined up in rows vertically in line
                39 Soldering Iron burns And Counting

                Comment

                  #9
                  Re: LG 42LN5700 issue

                  I guess since you guys think it is probably a diffuser issue I am going to take it down again and have a look, Not sure yet of what possibly could be wrong, But I will report any findings, or maybe document disassembly and reassembly?
                  39 Soldering Iron burns And Counting

                  Comment

                    #10
                    Re: LG 42LN5700 issue

                    If you disconnect the lvds cable from the t-con will the backlights stay on? If they will (and the tv stays on) you should be able to determine if it is a panel/signal or backlight/diffuser issue

                    Comment

                      #11
                      Re: LG 42LN5700 issue

                      so I did find one standoff that apparently came through by way of tv on its backside, and was floating around in there, I put it back and floated it back together and turned it on, and Unfortunately have same issue, the only difference between the old and new LED strips is that the old one's has a circle of diffuser material around each LED and the new one's do not, But i don't think that would cause an issue like this? going to try R_J's idea now and thank you for that by the way. any other idea's thoughts always welcome, thank you all, Very much appreciated.
                      39 Soldering Iron burns And Counting

                      Comment

                        #12
                        Re: LG 42LN5700 issue

                        Backlights do come on, Bright at first, then not so much but still visible. so here are some pictures with T-Con disconnected, so this points to Diffuser issue? should I take each piece of diffuser out, clean it and reassemble? I'm perplexed now, what else is new though LOL
                        Attached Files
                        Last edited by LITEZONER; 02-24-2020, 10:07 AM.
                        39 Soldering Iron burns And Counting

                        Comment

                          #13
                          Re: LG 42LN5700 issue

                          here some pics with panel removed forget the Horizontal flicker, it;s the vertical discoloration I cannot seem to find the cause of.
                          Attached Files
                          39 Soldering Iron burns And Counting

                          Comment

                            #14
                            Re: LG 42LN5700 issue

                            It could be the missing reflective circles. The darker bits are perhaps on the bends on the back metal sheet. The pattern is to even to be anything else.

                            Comment

                              #15
                              Re: LG 42LN5700 issue

                              If the bands are still there with the lvds cable disconnected, the fault can't be caused by a video issue, so this eliminates the main, tcon and lcd glass itself. It won't be a cleaning issue and cleaning may cause damage. Make sure the diffusers are in properly. The first one closest to the led's should be the thickest and have the dimples toward the led's.

                              I would remove the thin diffuser sheets and only place the thick sheet over the led's and if you still see the bands, it won't be a diffuser issue.
                              After seeing the latest pictures:
                              It does seem odd that the led intensity has brighter bands like that.
                              Last edited by R_J; 02-24-2020, 10:41 AM.

                              Comment

                                #16
                                Re: LG 42LN5700 issue

                                Well, not sure if you guys can see these led strips the way I do, there are discolored bands in them, almost a blue color going vertical on the left, right, and center. Very weird, let me know what you think of this
                                Attached Files
                                39 Soldering Iron burns And Counting

                                Comment

                                  #17
                                  Re: LG 42LN5700 issue

                                  Where did you get the strips? usually when the led's start to show blue they are at the end of their life. even in the pictures I can see a difference in the led intensity from one to another, this should not happen.
                                  Last edited by R_J; 02-24-2020, 04:10 PM.

                                  Comment

                                    #18
                                    Re: LG 42LN5700 issue

                                    Thank you all, so much for new led strips on eBay, getting a refund at least.
                                    39 Soldering Iron burns And Counting

                                    Comment

                                      #19
                                      Re: LG 42LN5700 issue

                                      Good to here about the refund, You might have better luck from shopjimmy

                                      Comment

                                        #20
                                        Re: LG 42LN5700 issue

                                        https://www.aliexpress.com/item/4000...archweb201603_

                                        Comment

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