LG LCD TV model 42LH3000, picture colours incorrect

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  • Slartibartfarst
    New Member
    • Dec 2013
    • 9
    • England

    #1

    LG LCD TV model 42LH3000, picture colours incorrect

    LG LCD TV model 42LH3000, picture colours incorrect

    I have had the above 42" LCD TV for just over 4 years and it has been working fine during that time until recently. While I was watching the TV, the picture suddenly started to display in the wrong colours (see attached photos).

    I have tried the following (with no effect):
    1) Used the option to reset the picture to default settings.
    2) Used the option to reset the whole TV to factory settings including re-tuning all the channels.
    3) Upgraded the firmware to the latest version.

    The fault now appears immediately the set is turned on (from cold).

    If you leave the set on long enough it looks like it might be going through a cycle as it does at some point briefly return to a normal picture before it continues on the cycle to incorrect colours again.

    I would appreciate any help or advice that you can offer.

    Kind Regards
    Attached Files
  • tom66
    EVs Rule
    • Apr 2011
    • 32560
    • UK

    #2
    Re: LG LCD TV model 42LH3000, picture colours incorrect

    Possibly GAMMA chip fail. Can you post a pic of T-con board?
    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

    • Slartibartfarst
      New Member
      • Dec 2013
      • 9
      • England

      #3
      Re: LG LCD TV model 42LH3000, picture colours incorrect

      Thank you Tom.

      I'm a complete novice with LCD TVs so I don't know what a T-con board is. Someone told me that they think there are 2 boards in my set - a main board and another one (the name of which I can't remember).

      If there are indeed 2 boards in my set would the T-con be the smaller of the 2? What does the T-con board do? Is that where the Gamma chip is? I've never taken one of these sets apart before, so I'm a bit reluctant in case I can't get it back together again.

      If the gamma chip is dead will I need to replace the board? If so are there generally any very awkward steps involved in replacing a board?

      Thank you

      Jeff

      Comment

      • tom66
        EVs Rule
        • Apr 2011
        • 32560
        • UK

        #4
        Re: LG LCD TV model 42LH3000, picture colours incorrect

        There is a main board, which has HDMI and the antenna connector on it.
        There is also a power board, which takes AC power in.
        There are boards for the buttons and lights - not particularly important now.
        Of most interest will be the board at the top of the panel, the t-con board.
        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

        • Slartibartfarst
          New Member
          • Dec 2013
          • 9
          • England

          #5
          Re: LG LCD TV model 42LH3000, picture colours incorrect

          Picture of the t-con board attached Tom.
          Attached Files

          Comment

          • tom66
            EVs Rule
            • Apr 2011
            • 32560
            • UK

            #6
            Re: LG LCD TV model 42LH3000, picture colours incorrect

            OK, see this picture. In the red area, and possibly a little outside it, there are points marked VG1 through VG22 (typically.) Please measure the voltage on each and report the reading for each. (Red circle around one point as an example.)

            To measure: multimeter on auto range volts DC or 20V DC (whichever it has), black probe on chassis, red probe on test point, note reading down. Rinse and repeat.
            Attached Files
            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

            • Slartibartfarst
              New Member
              • Dec 2013
              • 9
              • England

              #7
              Re: LG LCD TV model 42LH3000, picture colours incorrect

              I'm struggling to see such tiny connections Tom. I think I'm inclined to take the risk and spend £37 on a replacement T-con board. But I appreciate your efforts helping me to pin it down with more certainty.

              Thank you

              Jeff

              Comment

              • newtothis
                Badcaps Legend
                • Mar 2013
                • 1556
                • england

                #8
                Re: LG LCD TV model 42LH3000, picture colours incorrect

                I am picking up with of these sets tomorrow with the same fault, Will try helping you out once i get it

                I suspect T-con... Seems a weak point on these sets

                £37! I got one off the bay for £18 inc P&P

                Also if you look at the pic tom edited.. the little circle inside the bigger circle is a test point... they are the little round copper pads with VG10 etc next to them... check them all and report findings.

                These T-cons use the AS15 gamma chip and are prone to failing with the distorted colours, You can actually replace just the Gamma IC but need a few tools and be confident in fine pitch soldering to do so.
                Last edited by newtothis; 12-16-2013, 06:23 PM.

                Comment

                • newtothis
                  Badcaps Legend
                  • Mar 2013
                  • 1556
                  • england

                  #9
                  Re: LG LCD TV model 42LH3000, picture colours incorrect

                  To make it easier.... Click on the picture below..

                  I have highlighted a few of the VG test points... so you know what you are looking for.
                  Attached Files

                  Comment

                  • newtothis
                    Badcaps Legend
                    • Mar 2013
                    • 1556
                    • england

                    #10
                    Re: LG LCD TV model 42LH3000, picture colours incorrect

                    OK I have the TV... Same fault by seems of it.. AS15

                    Comment

                    • tom66
                      EVs Rule
                      • Apr 2011
                      • 32560
                      • UK

                      #11
                      Re: LG LCD TV model 42LH3000, picture colours incorrect

                      There are some others on the other side of the board, too. Need to test VG1 thru VG22.
                      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

                      • irep
                        Member
                        • Oct 2013
                        • 40
                        • portugal

                        #12
                        Re: LG LCD TV model 42LH3000, picture colours incorrect

                        I have in hands a 42LH3000 color problem, just checking voltage on Tcon, if it has voltage on VG test points and color not correct it assumes that a board problem?

                        Not power assy.
                        I´de like some help in this point.

                        Comment

                        • tom66
                          EVs Rule
                          • Apr 2011
                          • 32560
                          • UK

                          #13
                          Re: LG LCD TV model 42LH3000, picture colours incorrect

                          No, the VG will have a voltage regardless of working or not, but the specific curve of voltages they plot from 1-22 or 22-1 needs to be correct. If you post your values we can give some guidance as to whether they are correct or not.
                          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

                          • irep
                            Member
                            • Oct 2013
                            • 40
                            • portugal

                            #14
                            Re: LG LCD TV model 42LH3000, picture colours incorrect

                            some mesure:

                            VG1 - 15,22
                            VG2 - 15,10
                            VG8 - 9,99
                            VG10 -8,03
                            VG11 - 7,07
                            VG12 - 7,30
                            VG13 - 7,80
                            VG15 - 5,14
                            VG17 - 11,87
                            VG19 - 2,89
                            VG21 - 0,60
                            VG22 - 0,29

                            Comment

                            • tom66
                              EVs Rule
                              • Apr 2011
                              • 32560
                              • UK

                              #15
                              Re: LG LCD TV model 42LH3000, picture colours incorrect

                              The voltages are bad, so you will need to replace AS15 IC.
                              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

                              • irep
                                Member
                                • Oct 2013
                                • 40
                                • portugal

                                #16
                                Re: LG LCD TV model 42LH3000, picture colours incorrect

                                Ok Tom66, or get a new board.

                                Thanks you for the rapid answer.

                                Cheers

                                Comment

                                • tom66
                                  EVs Rule
                                  • Apr 2011
                                  • 32560
                                  • UK

                                  #17
                                  Re: LG LCD TV model 42LH3000, picture colours incorrect

                                  "New board" an expensive option as about half of them are bad (they are used parts.) Only if factory direct or LG direct.
                                  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

                                  • irep
                                    Member
                                    • Oct 2013
                                    • 40
                                    • portugal

                                    #18
                                    Re: LG LCD TV model 42LH3000, picture colours incorrect

                                    i will search on manual the reference number of chip and try to get it

                                    Comment

                                    • irep
                                      Member
                                      • Oct 2013
                                      • 40
                                      • portugal

                                      #19
                                      Re: LG LCD TV model 42LH3000, picture colours incorrect

                                      Tom66

                                      You are wright, i can get it in my country for 5 eur.

                                      Very nice price.

                                      Nice tip

                                      Comment

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