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LG 50PG20 Plasma "weird display only with inputs"

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    #1

    LG 50PG20 Plasma "weird display only with inputs"

    Hi im Chris and i will start by saying hi to this grate community, hopefully i can save this grate tv from this hart-breaking situation. :'(

    Ok so the Tv is a LG 50PG20 Plasma and it displays the menu system and Snow fine (when RF is selected with no input) but as soon as i apply any inputs after a few minutes the TV Displays a darker image with garbage and overlapping (back-light is still on) i can power cycle the unit and the display is fine again for a few minutes but the problem returns.

    on close inspection i can see that 1st LED on the input board is yellow (green and red together) and the 2nd LED comes on green but shuts off shortly after power.

    any help in narrowing the problem to a specific board so i can replace it is greatly appreciated.
    Tags: None
    #2
    Re: LG 50PG20 Plasma "weird display only with inputs"

    Originally posted by PhyChris View Post
    Hi im Chris and i will start by saying hi to this grate community, hopefully i can save this grate tv from this hart-breaking situation. :'(

    Ok so the Tv is a LG 50PG20 Plasma and it displays the menu system and Snow fine (when RF is selected with no input) but as soon as i apply any inputs after a few minutes the TV Displays a darker image with garbage and overlapping (back-light is still on) i can power cycle the unit and the display is fine again for a few minutes but the problem returns.

    on close inspection i can see that 1st LED on the input board is yellow (green and red together) and the 2nd LED comes on green but shuts off shortly after power.

    any help in narrowing the problem to a specific board so i can replace it is greatly appreciated.
    Service manual

    I don't trust 'eyewitness' descriptions; frequently they are inaccurate. I'd suggest posting several pictures. Note links in my signature and use 'Manage Attachments' (below the text entry area).

    1. A picture of the TV with the menu displaying.

    2. A picture of the screen with an OTA signal displayed as soon as power is applied.

    3. A picture of an OTA signal displayed after the picture goes bad.

    For what it's worth, all analog and digital inputs are processed on the main board and sent to the logic control card. Menus are also generated on the main board.

    PlainBill
    Last edited by PlainBill; 04-30-2011, 04:41 PM.
    For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

    Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

    Comment

      #3
      Re: LG 50PG20 Plasma "weird display only with inputs"

      Thank you for the quick reply. here are some Pic's of the tv

      this is the tv menu


      here is the tv when CAT is selected with no cable attached


      this is the tv with input before the problem (the image stays fine for 4-8 min's)


      and this is the tv after the problem (as you can see the TV's menus suffer from this effect as well)
      Attached Files

      Comment

        #4
        Re: LG 50PG20 Plasma "weird display only with inputs"

        dark pic...... zsustain issue?????

        Comment

          #5
          Re: LG 50PG20 Plasma "weird display only with inputs"

          ok so i have a test in mind that might help i just need an opinion if its a good idea.

          the control-board has an "auto-gen test pattern" that i can trigger (power off unplug main board power on and short two points on the board) so i turn the tv on with inputs and wait till the problem occurs then unplug the main-board (with power still on and hands insulated well) and run the control-board "auto-gen test pattern" to see if it generates a good picture.

          anyone else think this is a good idea? or can i damage more components trying to remove cables from an already powered set?
          Last edited by PhyChris; 05-02-2011, 04:46 PM.

          Comment

            #6
            Re: LG 50PG20 Plasma "weird display only with inputs"

            Originally posted by PhyChris View Post
            ok so i have a test in mind that might help i just need an opinion if its a good idea.

            the control-board has an "auto-gen test pattern" that i can trigger (power off unplug main board power on and short two points on the board) so i turn the tv on with inputs and wait till the problem occurs then unplug the main-board (with power still on and hands insulated well) and run the control-board "auto-gen test pattern" to see if it generates a good picture.

            anyone else think this is a good idea? or can i damage more components trying to remove cables from an already powered set?
            Bad idea; REALLY bad idea. I would disconnect the LVDS cable from the main control card, pt on the jumper and let it run. If it fails after some time you can be sure the problem is NOT the main board, and you have a merry chase figuring out what is bad. If it does not fail, the problem is almost certainly the main board.

            PlainBill
            For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

            Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

            Comment

              #7
              Re: LG 50PG20 Plasma "weird display only with inputs"

              ok so i ran the test the way you said and have some results! The problem still happens after a few minutes so i sat behind there and found that the 'Z-SUS' was making a buzzing noise that increased when the screen was displaying a full white picture and when the problem would occur that the 'Z-SUS' would go silent as if it shut down.
              so i ran another test, I powered up the TV with the with the 'Z-SUS' board disconnected and boom the screen looks the same way it dose when it have my hart-breaking problem

              to break it down encase i did not come across clear i can reproduce the exact same issue by powering up the tv with the power supply disconnected from the 'Z-SUS' board

              ok so how do i go from here? is there any way that an adjustment on the 'Z-SUS' board or power board can fix this? or should i just go and buy a replacement Z-SUS Board?

              Comment

                #8
                Re: LG 50PG20 Plasma "weird display only with inputs"

                the safe bet, yes replace the z zuztain board if you can find a new or good used one FROM A REPUTABLE SELLER.

                However... this may be worth looking at with a magnifying glass..

                Bieng this keeps working cold, and stops hot, you *might* have a cracked
                ( a.k.a. "cold") solder joint on that board. Resoldering it will fix it if that is the case, so this is worth checking..

                You will see various things but i will post some obious ones, caracterized by a ring or circular crack in the solder. In rare cases the solder will actually be fried and tarnished looking compared to the rest.


                Best of luck and happy hunting!

                ( also check power supply board pins where the power cable connects toat goes to the ysustian)
                Attached Files

                Comment

                  #9
                  Re: LG 50PG20 Plasma "weird display only with inputs"

                  Did anybody ever figure this issue out?? I am having the same issue on my lg 50pg20...
                  Don't want to have to start a new thread if the problem is already described on this thread!

                  My TV works great for the first 15-30 mins. but then looses the brightness and gets a pink/bluish pixelated look afterwards. Have to unplug it for a few days before it starts working well again and then looses the picture once again... what should I check first?
                  Try first? Could this be a power board issue?
                  Thanks

                  Comment

                    #10
                    Re: LG 50PG20 Plasma "weird display only with inputs"

                    Start your own thread, you'll get a better response. If you need parts, I have working good parts from my Lg 50PG20.

                    Comment

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