convert s-video to composite?

[Adam]

I've been watching alot of tv over the internet lately, and in a desire to actually watch it on a tv and not just my monitor, I swapped my video card for one with an s-video output. Now I just need to know how best to combine the chroma and the luma? Right now I just took some clip leads to the s-video cable and connected them to the luma only (which actually looks just fine on my b/w 1971 Zenith in the pic below)