TCON and self diagnosis!

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  • angelos
    Badcaps Veteran
    • Dec 2012
    • 567
    • South Africa

    #1

    TCON and self diagnosis!

    Hi Guys.
    I have experienced something rather unique and need to find out by the forum what to make of it.
    I got in this set, a JVC or Telefunken LED TV whose complaint is that sometimes the set comes up blank with the back lights running. So I switched on and yes there was a blank screen and back lights were running. I checked the fuse on the TCON and sometime later I lifted the set off the table to check the image (the TV has no feet to let it stand upright) and noticed the set was cycling red, green blue, test pattern, blank then all over again doing this. Suddenly the no signal logo appeared and tv was working perfectly fine. I switched off and later when i checked it again i noticed that the set was cycling again in "self diagnosis" mode.
    My questions are,
    1. How does a LED TV with a separate TCON board go into "self diagnosis" by itself? I realize that "self diagnosis" is generated by the TCON, right?
    2. Where to start fault finding? Main, LVDS, TCON, Panel?

    I have checked the blue / white LVDS pairs on the cable while TV was cycling and did not get 1.2V, it was 0V. This tells me that the main board is not sending the data to the TCON, right?

    Am i right in assuming that if you supply 12V to the TCON but with no data incoming the TCON starts to generate its own pattern?

    This fault is perplexing to say the least.
    Photo's can be uploaded later, i closed the set to do other work in the meantime.

    Regards
    Angelos
  • angelos
    Badcaps Veteran
    • Dec 2012
    • 567
    • South Africa

    #2
    Re: TCON and self diagnosis!

    So i guess the issue revolves around the main processor and voltages around it, core voltages etc?

    Comment

    • angelos
      Badcaps Veteran
      • Dec 2012
      • 567
      • South Africa

      #3
      Re: TCON and self diagnosis!

      Sorry, I guess it is not "self diagnosis" but rather burn-in mode

      Comment

      • Davi.p
        Hobbist Tech
        • Sep 2009
        • 4289
        • Italy - Milan

        #4
        Re: TCON and self diagnosis!

        Am i right in assuming that if you supply 12V to the TCON but with no data incoming the TCON starts to generate its own pattern?
        yes, check lvds cable..

        Comment

        • neilc6
          Badcaps Legend
          • Nov 2015
          • 1550
          • Canada

          #5
          Re: TCON and self diagnosis!

          It is called aging mode. Cranks the backlights to max and cycles through colors. Have accidentally turned it on in the service menu in a Haier. Exit on the remote or power button on tv to disable. If it's stuck in aging mode, then main board needs to be replaced.

          Comment

          • Davi.p
            Hobbist Tech
            • Sep 2009
            • 4289
            • Italy - Milan

            #6
            Re: TCON and self diagnosis!

            it is not aging mode here, is tcon self test, when tcons are powered with no video signal in, then starts self test.. it is common for many panels

            Comment

            • angelos
              Badcaps Veteran
              • Dec 2012
              • 567
              • South Africa

              #7
              Re: TCON and self diagnosis!

              Thank you Davi. I will check for a LVDS cable connection fault then i should be able to measure the differential signal on the main board if there are test points. Now i know how to test panels if the main board is non responsive. By applying 12V to the tcon without a signal applied.

              Comment

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