Modify Dreamcast RGB Scart?

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  • #52931
    Thanius
    Participant

    Hi, so I’m in a bit of a pickle.
    I previously had an OSSC to hook up my Dreamcast using SCART. Great picture, no sync loss or anything, been playing like this for the past 2-3 years.
    Now I’ve recently upgraded to a Retrotink 5X Pro and I can’t use the same cable any more as it has flickering image, and I’m afraid to blow up my setup.
    I then ordered a VGA/RGB cable with switch from eBay, but that cable isn’t compatible with my Dreamcast as it’s modified with a Dreampower PSU (not DreamPSU) and it seems like the cable is drawing too much power for the setup as the sound is really weird, like the CPU is being affected or something.

    So my question is, can I modify my old cable with a resistor and capacitor? I can’t find any guide specific for Dreamcast so would be nice if someone could point me in the right direction.

    Cheers!

    #52932
    BuckoA51
    Keymaster

    You have a flickering image, can you elaborate? A flickering image is not indicative of a cable that will blow up your system.

    OSSC requires a 75 ohm terminated SCART cable the same as the RetroTINK 5x does. You can open the SCART end of this cable and see if it has any components on the sync connection.

    VGA boxes do not draw more power, it seems to me like your Dreamcast may have some other issues.

    #52933
    Thanius
    Participant

    Hi, hard to explain. The image is nice and clear, but in the middle it’s like glitchy and pulls to the left. I’ve got a video of it I can put on YouTube. Anyways, I just opened up the cable and all there is are a capacitor on each RGB line, rated 220uF/10V.

    Nothing else, so it’s strange that it worked flawlessly on the OSSC (but come to think of it, it would lose signal once in a while.)

    How should I modify the cable?

    #52934
    Thanius
    Participant

    My Dreamcast is modified not only with a new PSU but also GDEMU clone.

    #53013
    Thanius
    Participant

    Here’s a video of the output

    So all I need to do is solder 450ohm resistor and 16v 220uF capacitor to pin 21?

    #53034
    BuckoA51
    Keymaster

    Well, wait a moment, are you sure the cable is even using composite sync, and not composite video for sync?

    #53037
    Thanius
    Participant

    I have no idea how this thing’s wired more than it’s only got capacitors on the RGB lines. Is there a schematics somewhere I can follow to properly wire it?
    The weird thing is that the cable works perfectly fine with OSSC

    #53048
    BuckoA51
    Keymaster

    Where did you get the cable from for starters? Unless you specifically got a cable wired for csync, it’s likely to be composite video for sync. You could confirm with a multimeter I think, http://members.optusnet.com.au/eviltim/gamescart/gamescart.htm#dcast

    #53049
    Thanius
    Participant

    It was mostly purchased from eBay gazillion and a half years ago. I’ll check that link and see if I can verify the wiring.

    I should be able to rewire it on the Scart side, right?

    #53058
    BuckoA51
    Keymaster

    Almost certainly it’s composite video for sync unless you specifically looked for a composite sync one. No, if you want to modify it for composite sync you’d need to change the Dreamcast end.

    However, RetroTINK 5x is perfectly compatible with composite video for sync.

    I have to suspect something strange going on with your Dreamcast based on what you told me about the other cable you purchased. Can you try another Dreamcast with the same cables?

    #55123
    Thanius
    Participant

    Some news on that new cable I bought, which I thought was incompatible. Turns out, after some research, that the pins on the motherboard to the PSU had oxidized and was making bad contact on some pins which caused the symptoms.
    All I had to do was add some solder to the pins and everything’s working as it should with the VGA cable. However, the retrotink was misbehaving in scart mode (it didn’t quite sync with the interlacing, causing stripy patterns) so I left it on VGA mode instead. Works great, now I only need to patch Skies of Arcadia since I’m running my PAL version.

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