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Composite to RGB conversion

Discussion in 'Electronic Repair' started by dsg, Oct 27, 2004.

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  1. dsg

    dsg Guest

    Hi.

    I'm guessing someone here might have some ideas on how to go about this.

    My TV does not seem to be able to split the Y and C signals from the
    composite input pin on the SCART connector. I get a black&white picture.
    However, my VCR does output a proper, colour picture to the set. I'm
    guessing that the VCR outputs RGB signals, and the TV is using those.

    So, I've been wondering about the feasibility of making a converter from
    composite video to RGB. I have not found such a circuit online, but I have
    found an IC that should be perfect - the MC44011. The problem, of course,
    is that it's been discontinued for a long time and I haven't found a
    supplier with a stock willing to sell me only 2-3 of them. I'd like it if
    someone could either help me get in touch with a supplier that can do
    this, or point me to other ICs that would be suitable. Being controllable
    from a micro is a big plus, as well as minimal external component count.

    Thanks,
    David
     
  2. Graham

    Graham Guest

    --
    Graham.



    %Profound_observation%


    Some PVR's output RGB, but I know of no consumer VCR that does

    I would rather concentrate on why your TV is not displaying composite PAL
    video in colour (I assume it's PAL 'cos you know how to spell 'colour')

    What model of TV is it? Some TV's can be switched in the menu, or by a
    hardware switch on the back, to accept S-Video signals to the SCART.

    In this configuration Luminance is expected on pin 20 and chrominance on 15

    As pin 20 is normally the composite input you can see why the picture would
    be monochrome.


    Graham.

    %Profound_observation%
     
  3. Craig Hart

    Craig Hart Guest

    Hi...
    What is the signal source that comes out in B&W?
    Are you also using the SCART input at this point?

    IMHO if it's a DVD player giving you black and white, I'd be 99% sure it's
    outputting the wrong standard eg NTSC, PAL-60 or whatever, and your set is
    expecting something different (eg PAL-50).

    Go thru the device setup menus and change the output type to match the TV.

    Craig
     
  4. dsg

    dsg Guest

    I've tried a DVD player, and the TV-out function of my computer's graphics
    card (though I don't really trust that).
    Yes, the SCART connector is the only input aside from the ant input.
    It's possible the devices are putting out NTSC or PAL-60... but would
    that really result in a black and white image? I'll connect the player up
    again later today, see if I can find some configuration for this.
    Thanks for the help, I'll post again with results.
     
  5. dsg

    dsg Guest


    Hi,

    Thanks for the suggestions. The set is indeed PAL. The problem is, it's
    some rebranded no-name set (says "mark" on the front, on the back there is
    a model number: "TBT2002 TXT", which google doesn't find anything for).
    I'm also quite sure I've seen the same set under a different brand name, I
    just don't remember where.

    The TV doesn't really have a config menu, and I couldn't find any switches
    on the back.

    Thanks,
    David
     
  6. Lionel

    Lionel Guest

    I'm sure that there are VCRs that output RGB, but I've never seen one. I
    think it's a lot more likely that your SCART cable is faulty, or
    something is set to NTSC instead of PAL, or vice versa.
     
  7. Lionel

    Lionel Guest

    Yes, so would I. Another possibilty is that the SCART cable is broken or
    not seated correctly, & the TV isn't getting all the colour data.
     
  8. dsg

    dsg Guest

    Well, it appears that the VCR is actually just outputting a composite
    signal. The problem (at least with the TV-output from the computer) was
    that it was only outputting an S-Video signal. With the DVD player, I
    assume it must be as others here have suggested, that it was outputting
    NTSC.

    Anyway, I guess I'll have to work out how to convert S-Video to composite.
    I found a simple schematic online (just connect a 470pF capacitor between
    Y and C, and tap the composite signal out of the Y pin). This doesn't seem
    to work for me, as I just get a black screen with some scrolling
    distortion. Has this worked for someone else here?

    Thanks,
    David
     
  9. Lionel

    Lionel Guest

    If your video card is a Matrox, they have a standard cable with both
    S-Video & composite outputs on separate connectors. If you hunt through
    the support section on their website, they also have the wiring diagram
    for it so you can make your own.
     
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