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How to verify a stable video signal ( NTSC / AV )

Discussion in 'Electronic Design' started by Boki, Jul 24, 2006.

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  1. Boki

    Boki Guest

    Hi All,

    My Video ( NTSC ) output (AV) seems not stable, when I keep a static
    picture there, I can see the picture is flashing ( something like the
    backlight flashing, about 10Hz...measured by my eyes.. )

    How to check the video signal is stable or not?

    Want to make sure that is power problem or circuit protect problem....

    Best regards,
  2. Down load the NTSC timing specifications, and check your signal with a
    scope, quite often published in philips semiconductor video IC specs,
    it sounds as if you have a major timing problem

    Get a proper TV signal from a TV tuner, and lock your oscilliscope to
    that, put your AV signal on the scope and see how quickly it drifts
    across the screen , or hire a Tektronixs(sp?) wavefrom monitor

  3. Maybe something is running at 50Hz vs 60Hz, or the other way.
  4. Guest

    Need a stable standard monitor
  5. Luhan

    Luhan Guest

    This sounds like a problem witht the monitor. The video signal itself
    is probably not the problem. I had a Radio Shack TV/Monitor that used
    to do this.

  6. Dammit, misread the OP, I thought Boki had created a video signal with
    a micro or some such evil device, and had problems with the signal

  7. Rich Grise

    Rich Grise Guest

    About 10 HZ sounds like you're seeing a beat between the power line and
    the vertical oscillator. Check the power supply for ripple.
    With your scope, look at the video itself - I've seen scopes that
    have "TV V" and "TV H" horiz. sweep settings; one syncs up to the
    vertical, the other to the horizontal, so you can see a side view
    of the frame or a top view of the lines. ;-) Any instability should
    show up there.

    Also, use the scope to check for ripple in the DC, both in the video
    source (although, if that were the case, you'd have seen it on the
    video itself) and in the monitor.

    If they're all OK, I'd start looking for an interconnect problem,
    and so on.

    Good Luck!
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