how can I make S-video mod for dreamcast?

[bshi02]

My S-Video cable for DC was broken(all of pins is break off) so I striped reserve normal S-video 4pin cable and cut the end to connect each 4 copper wire with broken wire of DC SV cable. I connected each wires by soldering several times but It failed because I couldn't know exactly which wire color is for Y,C and ground signal for s-video.(below image is normal SV cable which I cut on purpose in order to connect to broken dc cable.)
http://i214.photobucket.com/albums/cc280/bshi02/IMG_0341.jpg


I gave up to link broken DC S-video cable with normal cable.and I have heard that Dreamcast has soldering point of Y,C,Y and C Ground on mainboard but I can't read dreamcast mainboard diagram schematic so I don't know what is these S-video soldering point on the mainboard.
It is nearly impossible to buy dreamcast S-video cable in korea and I have very basic soldering skill.
Although There is considerable possibility of damage to mainboard with
my immatured soldering skill I want to make my own dreamcast s-video mod.
I photograph back and front image of my dreamcast mainboard.I want to know exactly where I should solder on mainboard in order to link with s-video port which would be added to DC back case.
http://i214.photobucket.com/albums/cc280/bshi02/IMG_0322.jpg
http://i214.photobucket.com/albums/cc280/bshi02/IMG_0325.jpg
I'm so sorry for my wierd English and
any help would be appreciated.
thanks in advance!