M421VT LED Screen Color Distortion

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  • dfang
    Member
    • Feb 2013
    • 39
    • USA

    #1

    M421VT LED Screen Color Distortion

    I have a VIZIO M421VT LED TV and it's got what I will call a color display distortion problem. I'm a novice at TV repair and would appreciate some advice with which direction to go with this one...Some times when it's turned on,,the picture is good,,then after about 20 min or so,,it will go to bad. I tried heating up main board,T-Con and PS with no noticeable effects.. Sound is good and all channels work..Any help appreciated..
    Attached Files
  • dfang
    Member
    • Feb 2013
    • 39
    • USA

    #2
    Re: M421VT LED Screen Color Distortion

    To scrap or not to scrap,,,that is the question..

    Could someone please give a educated guess as to what could be the problem ?

    Thanks..

    Comment

    • tom66
      EVs Rule
      • Apr 2011
      • 32560
      • UK

      #3
      Re: M421VT LED Screen Color Distortion

      I have seen this fault before caused by a loose ribbon cable (LVDS cable) between the main & T-con boards.
      Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
      For service manual, schematic, boardview (board view), datasheet, cad - use our search.

      Comment

      • dfang
        Member
        • Feb 2013
        • 39
        • USA

        #4
        Re: M421VT LED Screen Color Distortion

        Thank you Tom for the suggestion..
        I did notice a burn mark on the right side LVDS cable at the T-con..
        Cleaned the T-Con contacts and tried another cable,,no luck..Maybe the T-con eh ?
        Also the fault is still present with that LVDS disconnected on the other half of the panel..
        I can give more pics of components if needed..
        Thanks again.

        Comment

        • tom66
          EVs Rule
          • Apr 2011
          • 32560
          • UK

          #5
          Re: M421VT LED Screen Color Distortion

          LVDS cable runs from main A/V board (with HDMI inputs) to T-con... not from T-con to panel.
          Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
          For service manual, schematic, boardview (board view), datasheet, cad - use our search.

          Comment

          • dfang
            Member
            • Feb 2013
            • 39
            • USA

            #6
            Re: M421VT LED Screen Color Distortion

            Originally posted by tom66
            LVDS cable runs from main A/V board (with HDMI inputs) to T-con... not from T-con to panel.
            I stand corrected,,told you all I was a novice..
            Will check the LVDS from main to T-con..

            Comment

            • dfang
              Member
              • Feb 2013
              • 39
              • USA

              #7
              Re: M421VT LED Screen Color Distortion

              Well,,,I disconnected the LVDS Cable & reseated connections .
              I have the TV connected to my PC..This is weird,,when the TV is first turned on the pic is corrupted (as seen in pic first post) after about 5 min the pic clears up very nice and stays good so far for about 2 hrs.

              Comment

              • tom66
                EVs Rule
                • Apr 2011
                • 32560
                • UK

                #8
                Re: M421VT LED Screen Color Distortion

                Press and manipulate the cable while the set is running (do not remove it), does the fault change?
                Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
                For service manual, schematic, boardview (board view), datasheet, cad - use our search.

                Comment

                • dfang
                  Member
                  • Feb 2013
                  • 39
                  • USA

                  #9
                  Re: M421VT LED Screen Color Distortion

                  Originally posted by tom66
                  Press and manipulate the cable while the set is running (do not remove it), does the fault change?
                  Tried manipulating cable with no change..I also shut down and restarted computer after the TV has been working flawlessly for over 3 hrs now,,,and display is still good...Seems like it has to have heat...could the display panel be the culprit ? I will shut down set and give it a cool off period,,,then restart.

                  Comment

                  • tom66
                    EVs Rule
                    • Apr 2011
                    • 32560
                    • UK

                    #10
                    Re: M421VT LED Screen Color Distortion

                    If it is going to be anything it is most likely a main board problem or -possibly- a T-con board problem though I would say main board is more likely.
                    Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
                    For service manual, schematic, boardview (board view), datasheet, cad - use our search.

                    Comment

                    • dfang
                      Member
                      • Feb 2013
                      • 39
                      • USA

                      #11
                      Re: M421VT LED Screen Color Distortion

                      I just restarted after a 2 hr cool down and the pic stays bad for about 5 min then clears up.When it's not good,,,the distorted colors pulsate around the objects on screen,,,then it slowly gets less and less becoming perfect

                      A main board for this is about $100.00 from SJ...Gulp !
                      Thanks for your help Tom..

                      Comment

                      • newtothis
                        Badcaps Legend
                        • Mar 2013
                        • 1556
                        • england

                        #12
                        Re: M421VT LED Screen Color Distortion

                        Use a hair dryer across mainboard... it should clear quicker.... Next time try directing heat at smaller area using insert of toilet roll or similar... Circle smallest area on a pic for us.... May be able to repair

                        Comment

                        • dfang
                          Member
                          • Feb 2013
                          • 39
                          • USA

                          #13
                          Re: M421VT LED Screen Color Distortion

                          Will do the hair dryer treatment with toilet roll in hand in the morning concentrating on the main board..Good idea newtothis..I did try hair dryer to heat boards before,,but,,not a concentrated effort on the main...
                          I think we are on the right path..
                          I'll be back tomorrow...
                          Thanks again

                          Comment

                          • dfang
                            Member
                            • Feb 2013
                            • 39
                            • USA

                            #14
                            Re: M421VT LED Screen Color Distortion

                            I did some testing with my heat gun and toilet paper roll and came to the conclusion that indeed the main board is the fault. I used compressed air to cool down main board and the picture would go very bad when doing so..If I concentrated the heat on the metal shield,,the pic would clear up in short order.I preformed this test of cooling and heating many times and narrowed it down to what ever is hidden behind the metal shield...So...is there any repair for this board or should I bite the bullet and buy one off the net ?
                            Attached Files

                            Comment

                            • newtothis
                              Badcaps Legend
                              • Mar 2013
                              • 1556
                              • england

                              #15
                              Re: M421VT LED Screen Color Distortion

                              Most likely logic IC under there... from looking at the tracks anyway. Have the equipment to get that shield off?

                              Comment

                              • dfang
                                Member
                                • Feb 2013
                                • 39
                                • USA

                                #16
                                Re: M421VT LED Screen Color Distortion

                                Originally posted by newtothis
                                Most likely logic IC under there... from looking at the tracks anyway. Have the equipment to get that shield off?
                                Ok,,got the shield off,,big heat sink under it..Remove heat sink ?

                                Comment

                                • newtothis
                                  Badcaps Legend
                                  • Mar 2013
                                  • 1556
                                  • england

                                  #17
                                  Re: M421VT LED Screen Color Distortion

                                  Firstly try heat/cold directly at that heatsink

                                  Give is a pic too

                                  Comment

                                  • dfang
                                    Member
                                    • Feb 2013
                                    • 39
                                    • USA

                                    #18
                                    Re: M421VT LED Screen Color Distortion

                                    Originally posted by newtothis
                                    Firstly try heat/cold directly at that heatsink

                                    Give is a pic too
                                    I've done it now! Seems that after I removed the shield on the main board and reinstalled the board,,the TV will not power on...I get 35 VIZIO blinks when it's first plugged in then when I power on,,the VIZIO logo blinks once and that's it,,,Dead duck..I pulled the main back off and looked for a obvious problem,,but don't see anyting..Unfortunately I can't perform further test..I must have done something this main board didn't like..
                                    Attached Files

                                    Comment

                                    • newtothis
                                      Badcaps Legend
                                      • Mar 2013
                                      • 1556
                                      • england

                                      #19
                                      Re: M421VT LED Screen Color Distortion

                                      Ok check voltages at PSU - Main connector

                                      Comment

                                      • dfang
                                        Member
                                        • Feb 2013
                                        • 39
                                        • USA

                                        #20
                                        Re: M421VT LED Screen Color Distortion

                                        Originally posted by newtothis
                                        Ok check voltages at PSU - Main connector
                                        Ok,,tomorrow..
                                        Thanks for the help

                                        Comment

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