Generic question re DVI/VGA LCD's

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  • pedro
    Senior Member
    • Dec 2009
    • 199
    • AUSTRALIA
    #1

    Generic question re DVI/VGA LCD's

    I have a Samsung 172X on the bench with a weirdness that I can't explain (which is in itself no real surprise) but thought the assembled wisdom here may shed some light.

    When powered up with either a VGA or no signal, there appears to be a brief flash of a message box with a message about digital and then it blanks. The backlights can be forced on by overriding the BL_ON line but no pic present under these conditions. I don't have a DVI source handy to the bench to test with. It takes too many hands to override and turn on *and* try and watch the screen.

    So to the question: do dual input (DVI/VGA) LCD's ever get "stuck" in a state of expecting the DVI input only after previous use in that mode, and in so doing fail to recognise a valid VGA signal when presented?
    Friends don't let friends buy Samsung ....
    Tags: None
    • stj
      Great Sage 齊天大聖
      • Dec 2009
      • 31091
      • Albion
      #2
      Re: Generic question re DVI/VGA LCD's

      i'd look at any small caps near the vga signal path.
      the microcontroller is probably looking for a sync pulse to switch ports.

        Comment

        • Krankshaft
          Badcaps Legend
          • Jan 2007
          • 2328
          • USA
          #3
          Re: Generic question re DVI/VGA LCD's

          Doesn't the monitor have a 1 . 2 switch on the front panel to manually switch sources?

          I have had monitors that had an option on the OSD to set a default video input on startup. But if a source wasn't found there they would probably still search elsewhere.

          A flash of the backlights can be an inverter failure.

          When you forced the backlights on do all of them light?
          Elements of the past and the future combining to make something not quite as good as either.

            Comment

            • pedro
              Senior Member
              • Dec 2009
              • 199
              • AUSTRALIA
              #4
              Re: Generic question re DVI/VGA LCD's

              Originally posted by Krankshaft
              Doesn't the monitor have a 1 . 2 switch on the front panel to manually switch sources?

              I have had monitors that had an option on the OSD to set a default video input on startup. But if a source wasn't found there they would probably still search elsewhere.
              No there is no source selector, it is automagic.


              Originally posted by Krankshaft
              A flash of the backlights can be an inverter failure.

              When you forced the backlights on do all of them light?
              Inverter system is fine. When BL_ON is forced the display is even, suggesting both lamps are working, and the controller chip's protection doesn't kick in at all. (The BL_ON forcing doesn't impair the chip's protection mechanisms, and there is no f/b from the inverter/controller board to what I prefer to term the video board.)
              Friends don't let friends buy Samsung ....

                Comment

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