Samsung LN37A450C1D screen "dimming" issue

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  • Plocmstart
    New Member
    • Jul 2012
    • 5
    • US

    #1

    Samsung LN37A450C1D screen "dimming" issue

    I haven't been able to narrow down the source of this issue yet, and it's somewhat hard to describe but I'll do my best.
    The TV powers up and works fine for a couple minutes. Then the screen appears to get dimmer. It is NOT the backlight. I've taken the TV apart and viewed the backlight from behind the screen where there are a couple holes that are illuminated and it does not get dimmer. So I've ruled out the inverter and bulbs.
    When I look closer at the screen I see when it's normally working all the pixels appear to be lit. When it gets dimmer it appears that only every other column of pixels appears to be lit, and at times it even appears that they are shifting which ones are on and which ones are off by one column, as if the image were vertically interlaced.
    The update rate also appears to decrease significantly. Sports shows can get blurry in high speed motion when the issue is present.
    If I have the menu up prior to the issue happening and then it starts going bad and I close the menu I get somewhat of a ghosting effect, where the "off" columns don't appear to have turned completely off.
    I'll try to get a picture if at all possible, though getting a macro shot of individual columns might be hard.

    So far I have disassembled the TV down to the panel and probed the voltages where I would expect there to be 3.3V, 12V, 24V, etc. and everything appears to be good when it's both working and not.
    So I'm left guessing if it's the T-CON board, maybe the main board not transmitting a good LVDS signal, or maybe even a bad power supply I haven't found yet. I haven't gone as far as borrowing the 1GHz scope from work yet, but it may come to it. The service manual I have only has a schematic for the main board, and it's the typical "if this doesn't work replace board X" type manual.

    The TV is still watchable, but definitely dimmer and less high-def in its current form. I'd like to return it to its proper state though if possible. Any help is appreciated.
  • senndogg
    Badcaps Veteran
    • Dec 2011
    • 383
    • Albania

    #2
    Re: Samsung LN37A450C1D screen "dimming" issue

    who has manufactured the panel? Chungwa, Chi-mei, Samsung?

    Comment

    • JimmysTGP
      Member
      • May 2012
      • 45
      • US

      #3
      Re: Samsung LN37A450C1D screen "dimming" issue

      Clean and reseat all your Ribbon cables. The LVDS cable and the cables going out of T-con to panel, but definitly sounds like a T-con possible panel issue, I don't think its your PS or your main. Also post up some Pics of this problem

      Comment

      • Plocmstart
        New Member
        • Jul 2012
        • 5
        • US

        #4
        Re: Samsung LN37A450C1D screen "dimming" issue

        It's a CMO panel. I've completely disassembled and reassembled the TV down to the panel, so I've tried removing and reseating all connectors multiple times now. The PCB connected directly to the LCD was bowed a bit, so I relieved the strain on that board during reassembly but it didn't seem to make a difference.
        I managed to get a photo of some of the pixels in focus. It actually looks like every row is interleaved, and possibly multiple rows are repeated unless the pixels are rectangular.
        Thanks for the help!
        Attached Files

        Comment

        • tom66
          EVs Rule
          • Apr 2011
          • 32560
          • UK

          #5
          Re: Samsung LN37A450C1D screen "dimming" issue

          I've seen these panels - never liked the look of them, motion is awful and you can see the dot-crawl on fast movement. My guess would be T-con as it is more global. Panel issues are less rare when they cover the whole 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

          • Plocmstart
            New Member
            • Jul 2012
            • 5
            • US

            #6
            Re: Samsung LN37A450C1D screen "dimming" issue

            Thanks tom66. Yes motion is horrible and if I move my head in any way while watching it I can also see the pixel blur even worse. I'll try picking up a new T-con and report on if that fixes it. Thanks!

            Comment

            • tom66
              EVs Rule
              • Apr 2011
              • 32560
              • UK

              #7
              Re: Samsung LN37A450C1D screen "dimming" issue

              Originally posted by Plocmstart
              Thanks tom66. Yes motion is horrible and if I move my head in any way while watching it I can also see the pixel blur even worse. I'll try picking up a new T-con and report on if that fixes it. Thanks!
              And Samsung sells their products at massive premiums! Rip-off!
              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

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