ATARI ST with SCART gets wobble video

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  • #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?

    #49211
    BuckoA51
    Keymaster

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

    #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.

    #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.

    #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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