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Thread: C64 S-Video

  1. #1

    Default C64 S-Video

    Is there a definitive method or solution to hooking up your C64 to an S-Video input on a TV?

    I have a C64 that I am going to start working on (I need a PSU and a drive solution still), so I want to start planning and buy what I need to do a video output mod. I'm going to be hooking it up to a CRT with an S-Video input. I have a later model long board C64 with the newer RF modulator.

    I have found different accounts of what should be done and why it should be done. This is what I have been able to find out (true or not) so far:

    1) The chroma output from the C64's voltage is too high and I will need to alter the resistor values around the chroma output trace inside the RF box (which also contains the YC generation circuit).

    2) There are some delay differences between the Y and the C lines out of the VIC II chip because Commodore wasn't shooting for S-Video spec as it hadn't been created yet. I haven't seen a fix for this anywhere, but I assume that, if it's true, then it must be possible to introduce some controlled delay to make it sync properly. I can't even tell if this is a real problem or what visual issues it would cause, but I've seen it mentioned in a couple places.

    3) The bandpass filter between the chroma output on the VIC II and the chroma amp transistor is intentionally limiting the bandwidth of the signals and should be removed.


    Is there anyone here who can help me make a decision about what path to follow?

    Thanks

  2. #2

    Default

    Do you have the 5 pin C64 or the 8 pin C64? A guy over at the lemon64 forum helped me get my 5 pin outputting a decent s-video signal, then I found a Commodore 1702 it is working with well too.

  3. #3

    Default

    Quote Originally Posted by alank2 View Post
    Do you have the 5 pin C64 or the 8 pin C64?
    8 pin. The 5 pins are only on the earliest C64s AFAIK.

  4. #4

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    The guy that helped me at the lemon64 forum was r.cade. You might want to ask this question over there under help and support. He basically weakened the luma by putting suggesting a 25 ohm resistor to ground. I think I used 33 ohms and it turned out great for s-video. I do not know if this applies to the 8-pin, but I somewhat recall some of the 8-pin cables having a resistor inline, so you might search c64 s-video and look for 8 pin pages.

  5. #5

    Default

    Quote Originally Posted by alank2 View Post
    I somewhat recall some of the 8-pin cables having a resistor inline
    I have seen those cables. The pages I read referring to the resistors in cables typically recommend a ~300 ohm resistor, but I found a couple pages stating that the C64s actually output a fairly wide tolerance chroma signal and that it really takes measuring the output to get it correct for each system. I suppose that would mean that the Commodore monitors could accept a pretty wide range.

    What I'm hoping to find is a yes or no on these different methods from those who have trod this ground multiple times. I guess you're right and I should probably go to a Commodore specific place. I just don't have that forum membership as of yet, so I thought someone of those people might check over here.

    Thanks

  6. #6

    Default

    It wasn't too hard to get setup over there as I recall. I think the resistor values in the cable were larger like you said around 300 ohms or so. I was a little concerned to go that low with my 5 pin, but presumably he has been running that configuration for a long time and I went a little larger for some margin. I do recall coming across a lot of website talking about c64 s-video, so you might try a google search to see what you can discern from that. Almost all of them were talking about the 8-pin. I think there are even 8-pin s-video cables on eBay (maybe they have the resistors in line? maybe not?) Good luck!

  7. #7

    Default

    Quote Originally Posted by alank2 View Post
    I do recall coming across a lot of website talking about c64 s-video, so you might try a google search to see what you can discern from that.
    Thanks!

    Yes, I've been down the google road. This was more of a "I've googled all there is too google and I want to make sense of all of the potentially conflicting things that I've read" type post.

  8. #8

    Default

    Ray Carlsen builds C64 s-video cables. You can ask him whether adding a resistor to your monitor set-up is necessary.

    Truly,
    Robert Bernardo
    Fresno Commodore User Group - http://www.dickestel.com/fcug.htm
    Southern California Commodore & Amiga Network - http://www.portcommodore.com/sccan

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