ATARI ST with SCART gets wobble video

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  • September 9, 2021 at 8:53 PM #49196
    AndresVettori
    Participant

      Hi I have post a video https://youtu.be/F3bQY7WdCDI showing the issue.
      This behavior could be caused by some RGB lines needing to pass through a resistor?
      Building the cable I have not put any resistors for RGB signals or CSYNC.

      That might be the cause?

      September 10, 2021 at 2:37 PM #49211
      BuckoA51
      Keymaster

        Could be any number of things unfortunately, what is the pin out from the ST? Where did you tap sync from?

        September 10, 2021 at 4:29 PM #49212
        AndresVettori
        Participant

          I’m using this connection: http://info-coach.fr/atari/hardware/interfaces.php#scart_peritel_cable
          CSYNC (pin 20 on SCART) is coming from CSYNC on pin 2 from the Atari DIN.
          I have read on some other posts about people having the same issue and seems related to some desync on the video signal clock that could be adjusted by some variable capacitor C117.

          It’s explained in this thread: https://www.atari-forum.com/viewtopic.php?t=33234

          Will try to follow those instructions and see what happens.

          September 12, 2021 at 11:33 AM #49241
          BuckoA51
          Keymaster

            Check the voltage from pin 2 (if it is composite sync on your ST and not composite video) make sure it’s within consumer specs. Often sync from computers is TTL voltages not 75 ohm.

            September 14, 2021 at 5:33 PM #49291
            AndresVettori
            Participant

              Added some resistors to RGB & CSYNC signals (also improved the cable shielding) and the quality is a LOT better now.

              Thanks!

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