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    LG 42LW5500 strange problem

    Hello everyone,

    I have bought a replacement mainboard (used state) from ebay for a LG 42LW5500 TV.

    Previous mainboard had the typical LG problem (cpu bga soldering - no video , no backlight at startup)
    Used heat gun. Worked for a month
    After that stuck at startup LG logo (Found out from internet is linked to the same problem)
    Heated again , but I guess I reheated wrongly (at higher degrees that I should have).
    It didn't work anymore.

    So, I have bought a new mainboard from ebay.

    And this is how it behaves (I have attached also 2 pics)
    https://streamable.com/vabveb

    The seller says it could be panel incompatibility and says to change it from Service Menu
    (but I haven't sent him a video, just some pictures, so I don't think he really understood how it behaves)

    The problem is that the image is rarely steady and correct, so that you could distinguish things. It is only for a second and then a few more is indistinguishable.

    It happens rearly to be steady constantly from startup to power off (only if I set it on HDMI input (with no signal)).

    It is then when I manage to distinguish something and could enter LG Service Menu, InStart and EZAdjust (using android app) and possibly alter things.
    But I don't know where to change any panel related settings (Tool options 1, attached pic, seems to be something, but it is set correctly 42 and LW55)

    I also tried replacing the Tcon (bought a pretty cheap one)
    (Measured a couple voltages on the Tcon, that were not constant (varied for a small amount))
    But it is the same.

    Where could this problem come from?

    Is it the mainboard, should I send it back? or could be something else, something at my side.
    With the previous mainboard at second heating some pieces fell (somewhere very small), tried soldering them back, tried the board again and made a short on lower part of the mainboard (a power controller); I don't know if that could have affected somewhere else (as I said I already tried replacing the tcon)

    If anyone has any idea to give, where this problem could come from, would really appreciate it.

    From my attached video you could see
    When here are moments (maybe in a time pattern or depending on the content (image colors etc)) when the image is steady and also becomes better quality (as you could see at 0:43 the image quality is better than before)
    Also If you look closely the image (tv source and also tried HDMI pc input) has a few good lines missing from below (horizontally) and from right (vertically); TV has 1980x1080 resolution.

    Thank you.
    Attached Files

    #2
    Re: LG 42LW5500 strange problem

    if service menu is steady set to correct panel .

    Comment


      #3
      Re: LG 42LW5500 strange problem

      Did you try changing from 10 bit? it might show clear as soon as you change it, if it don't, probably put it right back like it was, did you try a factory reset and firmware update if available?
      Last edited by nomoresonys; 06-14-2020, 07:22 PM.

      Comment


        #4
        Re: LG 42LW5500 strange problem

        Originally posted by petehall347 View Post
        if service menu is steady set to correct panel .
        Where should I try change Panel Type? In what Options?

        In the first attached picture I am in Tool Options 1, In EZAdjust

        I guess that is where I could change panel size, model LW LV etc, and bit type

        And it is set correctly.

        Comment


          #5
          Re: LG 42LW5500 strange problem

          Originally posted by nomoresonys View Post
          Did you try changing from 10 bit? it might show clear as soon as you change it, if it don't, probably put it right back like it was, did you try a factory reset and firmware update if available?
          Yes I did try setting to 8 bit.
          it doesn't change things in better. Just a more unclear, green look
          It almost made it imposible to distinguish something (and I mean when the picture is steady from power on, cause otherwise you can't do anything).

          These are the options for panel type or where else should I look?

          Comment


            #6
            Re: LG 42LW5500 strange problem

            How do the stickers numbers on each mainboard match up? some mainboards just don't interchange, wonder if it could be a tcon issue? Maybe try cleaning and reseating the tcon ribbon cables with some isopropyl alcohol, not to vigorously they can be delicate and make sure the lvds cable from tcon to mainboard is secure and clean.
            Last edited by nomoresonys; 06-15-2020, 04:32 AM.

            Comment


              #7
              Re: LG 42LW5500 strange problem

              Originally posted by nomoresonys View Post
              How do the stickers numbers on each mainboard match up? some mainboards just don't interchange, wonder if it could be a tcon issue? Maybe try cleaning and reseating the tcon ribbon cables with some isopropyl alcohol, not to vigorously they can be delicate and make sure the lvds cable from tcon to mainboard is secure and clean.
              The stickers, serial numbers, etc are all exactly the same.

              I know this mainboards are used in 32,42,47 maybe even 55'' inch LGs

              but the ebay seller speciefed is from a 42LW5500 TV.

              Tcon as I have said I have replaced. And still the same problem.
              A couple of Voltages on Tcon are not stable (with the replaced one as well).
              I don't know if that is normal.

              There are 2 LVDs cables from mainboard To tcon.
              One has 51 connectors and the other one has 41.
              (on the 51 there are VCC and SEL and other)

              The 41 connector tried to unplug it and there is not much difference to the picture. Without the larger one image is unavailable, but that is normal due to panel VCC.

              here is the schematics from the mainboard.
              https://servicemanuals.us/lg/tv/42lw....html?start=41

              Comment


                #8
                Re: LG 42LW5500 strange problem

                but the ebay seller speciefed is from a 42LW5500 TV.
                The screen menu is showing 42LW5500-ZE which may not be the same set as the 42LW5500.

                I have an LG43LH5100 set where the mainboard for an LG43LH5100-ZE is quite different

                Check your EAX....... and EBT....... numbers against the original board.
                Last edited by dick_barton; 06-15-2020, 08:48 AM.
                Willing to help but I'm no expert.

                Comment


                  #9
                  Re: LG 42LW5500 strange problem

                  Originally posted by dick_barton View Post
                  The screen menu is showing 42LW5500-ZE which may not be the same set as the 42LW5500.

                  I have an LG43LH5100 set where the mainboard for an LG43LH5100-ZE is quite different

                  Check your EAX....... and EBT....... numbers against the original board.
                  It is in fact a 42LW5500-ZE LG Tv (I didn't mention that exactly)

                  And the mainboards old and new (EAX, EBT numbers) are exactly the same.
                  It is how I have searched ebay for it (using those numbers)

                  Comment


                    #10
                    Re: LG 42LW5500 strange problem

                    I have found similar looking problems on youtube
                    here https://www.youtube.com/watch?v=04s8c11xJyY
                    it sais it resolved with baking mainboard in oven

                    and here https://youtu.be/IN2yuzmjHxw
                    this looks very similar with my problem (i guess my tv image is with more noise, from the start)
                    but there are no comments here

                    Could it be the BGAs (cpu, and another chip that lvds signal enter in it) from the mainboard that could produce this problem ?
                    Or is it incompatible panel ?

                    My previous mainboard had the no backlight no video, then the stucked logo, and these all came from the main BGA (cpu)

                    Comment


                      #11
                      Re: LG 42LW5500 strange problem

                      I wouldn't be surprised if you bought a bad mainboard, not everyone tests them or even has a way to test them.

                      Comment


                        #12
                        Re: LG 42LW5500 strange problem

                        Originally posted by nomoresonys View Post
                        I wouldn't be surprised if you bought a bad mainboard, not everyone tests them or even has a way to test them.

                        Just making sure it is nothing on my side, before sending the motherboard back

                        I am trying to understand if this kind of problem could be anything else related other than the mainboard (panel maybe)

                        Because on my previous mainboard after I tryied heating the main BGA (CPU) a second time, it made a short (burned power controller)
                        I don't know if that could have afected anything else on other boards (panel , tcon - have changed it though, power source)

                        There are non steady voltages on the Tcon board.
                        Could those be from the panel somehow?
                        Could the panel become afected from a short on the mainboard?

                        Comment


                          #13
                          Re: LG 42LW5500 strange problem

                          Did you unhook the tcon from the panel and see if the voltages are the same?

                          Comment


                            #14
                            Re: LG 42LW5500 strange problem

                            Originally posted by nomoresonys View Post
                            Did you unhook the tcon from the panel and see if the voltages are the same?
                            Yes, I tried that today.

                            The voltage is constant when the panel is disconnected from tcon.

                            When connected, it's interesting that it varies, it gets higher exactly when the picture on screen is steady (you can distinguish a picture, as you could see in the video from time to time, for 1,2 seconds)

                            Should I suspect the panel? from that short on the initial mainboard (the one I've changed).

                            I don't want to make the ebay seller think it's his fault* if it's not.But if it's the mainboard I should rush a bit to send the board back (I have it already for 14 days). But could this problem come from there.

                            I finally found this vid (https://www.youtube.com/watch?v=IN2yuzmjHxw) I've mentioned before, that looks very similar with my problem (at power on it looks almost exactly like my tv)
                            , posted in this forum:http://www.ebastlirna.cz/modules.php...topic&t=79569\

                            Someone is saying it is the panel.

                            Comment


                              #15
                              Re: LG 42LW5500 strange problem

                              I did the panel test like it's specified in this ebook https://cdn.badcaps-static.com/pdfs/...d6ef3fc97d.pdf
                              jumped 12V and 3.3V on pin 44 (CN1 - lvds connector with 51pins)
                              red green blue white black pattern are ok
                              so the panel is ok.

                              Measured Tcon 6870c-0358a voltages
                              ()
                              they are all how they should be. (28v, -5v, etc)

                              1 voltage varies, but only when LVDs are conected , from 1.6v to almost 3v

                              So, it's not the panel or the T-con.
                              It's the mainboard.
                              Now I am sure about this.

                              Comment


                                #16
                                Re: LG 42LW5500 strange problem

                                Nice work, yes I would send it back.

                                Comment


                                  #17
                                  Re: LG 42LW5500 strange problem

                                  The ebay seller (store) was kind enough to refund the money and leave me the mainboard as well.

                                  Now the question is what should I do in order to try and repair this problem (if it could be repaired)

                                  These motherboards have a common CPU connection problem (no video, no backlight or still startup image) that usualy is solved with heat gun or in the oven (from what I've seen on internet)

                                  I suspect this could also come from bad connections of CPU or the other BGA, and I would try and heat them.

                                  CPU
                                  BCM35230 - 0,4mm ball
                                  the other BGA
                                  LGE7303C - 0,6mm ball BGA

                                  What temp (celsius) should I apply and for what time?
                                  Should the heating of the 0,6mm ball be the same as for the CPU?
                                  I will start with the CPU anyway and see from there, if there aren't changes, I'll heat the other bga.

                                  Or if anyone has other ideas what source this problem could come from, please let me know.
                                  As I said before, the mainboard is the cause (power source, panel, t-con are all ok)

                                  Comment


                                    #18
                                    Re: LG 42LW5500 strange problem

                                    Many videos on youtube about heating those chips, probably need to gradually bring the temp to 217°C/422°F for about 40 seconds maybe and gradually back off to try to keep the possibility of thermal shock down, so gradually bring it up heat it for 40 seconds then gradually back off, check some of those videos.

                                    Comment


                                      #19
                                      Re: LG 42LW5500 strange problem

                                      Originally posted by nomoresonys View Post
                                      Many videos on youtube about heating those chips, probably need to gradually bring the temp to 217°C/422°F for about 40 seconds maybe and gradually back off to try to keep the possibility of thermal shock down, so gradually bring it up heat it for 40 seconds then gradually back off, check some of those videos.
                                      Thanks for the answer.
                                      Ok, I will look but I am also looking from answers in here to understand what is better and normal
                                      On youtube I could posibly find maybe untrue unreal even stupid things.

                                      Also found here in forum a post https://www.badcaps.net/forum/showth...68717&p=817319
                                      where someone was saying to heat at 350C ? (exactly for this bga chip)
                                      What is that about?

                                      Comment


                                        #20
                                        Re: LG 42LW5500 strange problem

                                        It's strange, one guy on here heated to I think he said 450C, he said it worked for a while then quit, so he heated to think he said like 900C and it worked, I would have thought 900 would be way too high, unless his heat sensor was out of whack??
                                        Last edited by nomoresonys; 06-21-2020, 03:04 PM.

                                        Comment

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