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Help with an RGB Conversion...

Discussion in 'Electronic Design' started by trelster, Aug 12, 2006.

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  1. trelster

    trelster Guest

    I am the owner of a recording studio in Minneapolis and we just
    purchased a new (to us) recording console. The console is 20 years old
    and runs off of a computer the same age. We've been trying to find a
    solution for a video feed from RGB outputs. I have talked to every
    electronics outfit in town, scoured the internet (including Google
    Groups) and haven't been able to find a definitive solution for this.
    Seems there are a number of different scenarios, and I would greatly
    appreciate some help on this.

    Here is the best I can describe what we have...

    There are (of course) the 3 R, G and B outputs on the computer. In
    addition, there is 1 Sync output, only 1. We have a 5 (one too many)
    BNC to VGA cable, but I believe this is typically used to send signal
    from VGA to RGB (right?). Along with the R, G & B on this cable, there
    is a Vertial and Horizontal. We've tried connecting this cable to a
    newer VGA monitor in a number of ways. There are 2 cases where we see
    anything at all. First, when we connect any one of the colors to the
    Sync we do see staticy Horizontal lines of that color. Also, when we
    connect the Vertial Cable to the single sync output, the monitor
    indicates a "frequency out of range" error. We are, on the other hand,
    able to get a clear and steady signal on and older monochrome monitor
    using a Single BNC to Single BNC cable, if we connect this cable to the
    Green BNC output on the computer. We also get signal on the red and
    blue, however the image isn't stable.

    In any case, I'm looking for the most cost effective solution. I have
    found a couple of older RGB monitors on Ebay, but all seem to have only
    the 3 (R, G & B) inputs without the Sync input to match the Sync output
    on our computer. If this will still work, great. We'll buy one. I'm
    concerned about that fourth (Sync) output however.

    Can someone tell me definitively if buying one of these monitors will
    work? And if not, what a good cost effective solution would be?

    Many thanks!

    A440 Studios
  2. You must have a Sync-on-green output, then. I don't know why would they
    have a separate sync, then, but those sync-on-green monitors will probably
    work for you, unless the frequencies your computer outputs exceed the
    monitor specs. Can you measure the frequencies on the green and sync

    Also, there are adapters from SoG to VGA, which has separate R,G,B,Hsync
    and Vsync signals. This one might do:
  3. How about this? Its not my design but I did use it before. A 2N3904
    works in place of the BC548.

    100 uF
    ! !
    Green ----! !---------------------------------
    -! !+ !
    680E !
    BC548 !
    HSync ------------- __---------/\/\------o--------- CSync on Green
    \ /!
    \ /
    1k !
    VSync ----/\/\----------

    [note by the poster: for those guys who know exactly as much about
    as me, BC548 is a transistor, the /\/\ 's are
    and the 100uF is a condensator. :)

    This one works perfectly without _ANY_ logical circuits and thus needs
    _NO_ 5 Volts or anything else ... ;)

    Note: This works only with syncs that are active low, but since this is
    the default for _any_ sync signal, you would not have to expect any
    problems with this circuit.

    Note2: when you build this with SMD you can put the whole circuit in the
    VGA connector of the cable. ;)

    so long, MadMax. >>>--- for questions contact this guy!
  4. Guest

  5. Guest

    I have a working older Veiwsonic model 20G color monitor that uses 5
    input cables that sounds like what you are looking for that I might be
    willing to part with for the right price. I measured diagonally across
    the part of the screen that is visible and it measured about 18 inches.
    Let me know if you are interested Send email to
  6. Two things, 1) It could be a composite sync output, 2) since it's video the
    system probably outputs stuff at 50 Hz which is too low for a modern VGA
    You could try finding more information on the computer in the console (it
    could conceivably be an Amiga 1000 for example). Also you could try
    measuring the vertical & horizontal sync frequencies (eg using a 'scope) so
    you have an idea what specs the monitor you're buying will have to handle.

    Daniel O'Connor software and network engineer
    for Genesis Software -
    "The nice thing about standards is that there
    are so many of them to choose from."
    -- Andrew Tanenbaum
    GPG Fingerprint - 5596 B766 97C0 0E94 4347 295E E593 DC20 7B3F CE8C
  7. John B

    John B Guest

    trelster scrobe on the papyrus:
    At that age and with four wires it is most likely to be a TV standard
    RGB and composite sync signal. Either 525/60 or 625/50 depending on the
    country of origin. If you have access to a scope take a look at the
    sync signal and see what the frame rate is and how many equalising
    pulses there are in each field sync. 525/60 has six equalising, six
    field serration and six equalising. 625/50 has five of each. Either way
    a cheap CCTV monitor should work correctly, although you may have to
    adjust the vertical frequency to get it to lock.
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