No sync from C64 via RGB converter

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  • #22400
    MagerValp
    Participant

    I have an OSSC 1.6 that works great with my Amiga, but I’m having trouble getting a C64 to work. It’s hooked up via a JVC KM-V7EG S-Video to RGB converter, but the OSSC just says “NO SYNC”. I’ve tested the JVC RGB converter on a TV with SCART, and it works beautifully there. It also works with one of those cheap and cheerful SCART to HDMI converters, though it occasionally seems to drop sync. I coded a small test program to display gray bars and hooked it up through an S-video switch for testing so I can use my S-video monitor at the same time, and made some measurements with my pocket scope:

    https://ibb.co/jjU9HT

    Sync

    #22405
    MagerValp
    Participant

    The forum breaks the images links when I post them for some reason, so plain URLs here:

    Setup: https://ibb.co/jjU9HT
    -133 mV sync: https://ibb.co/ePg0P8
    Luma: https://ibb.co/gvVGxT
    64 µs scanline timing: https://ibb.co/kS6Zj8

    #22407
    BuckoA51
    Keymaster

    I’m not familiar with that transcoder, have you tried playing with Sync Analogue Sync Vth and Vsync Threshold under sync options?

    #22418
    MagerValp
    Participant

    Ah, good call! I nudged down the Vth from 123 to 112 mV and it recognizes it as 311p @ 50.27 Hz. After increasing H-PLL Pre-Coast to 4 and Post-Coast to 2 I get a good picture at 2x/3x/4x/5x ??

    I get a pretty strong checkerboard pattern, so I’m ordering a LumaFix64 as well.

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