Diode inline with composite video feed?

Discussion in 'General Electronics Chat' started by BlInK311, Feb 26, 2013.

  1. BlInK311

    Thread Starter New Member

    Jul 31, 2012
    8
    0
    Hey guys,
    I was analyzing a wireless video board that has an analog (composite) video input and output. While doing so, I found that the video feed line has an inline diode. Cathode toward the Video Input side and Anode toward the Video Output side.

    The video input goes to both the diode and the wireless board. If the Diode wasn't there, then the video input and output would be a straight through connection.

    I am very confused why its there. Can anyone explain this to me?

    Thanks in advance.
     
  2. BlInK311

    Thread Starter New Member

    Jul 31, 2012
    8
    0
    Inserting an image so you can see whats going on and hopefully explain why its there.

    EDIT: The connector on top is VIDEO OUTPUT!!!. Not video input. my bad
     
  3. w2aew

    Member

    Jan 3, 2012
    219
    64
    It is probably being used as a switch. A DC forward bias turns it on, and 0 or reverse DC bias turns it off. I just happened to have made this video tonight to describe how to use a diode as a switch.
    http://www.youtube.com/watch?v=YBNIq_d56sA
     
  4. timescope

    Member

    Dec 14, 2011
    298
    44
    Are you sure it is a diode ? Test it with the resistance range of a multimeter. It could be an inductor.

    Timescope
     
  5. w2aew

    Member

    Jan 3, 2012
    219
    64
    Looking at the picture, it looks to be a tantalum capacitor, not a diode. Nevermind on the diode switch video...
     
  6. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    5,435
    1,305
    Yep, it's a 100uF 6v tantalum cap in SMD size D.

    Sigh, does knowing that make me a nerd?

    It's common to use a cap in series with an analogue input.
     
  7. BlInK311

    Thread Starter New Member

    Jul 31, 2012
    8
    0
    Thank you guys!! That makes total sense.
    I appreciate all of your help.
     
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