I've been trying to connect my mbp to a quite old tv set, but it doesn't seem to work.

I'm using the DVI-VGA adapter cable which came with my mac, and a VGA-RCA/S-video cable that I've purchased. After I'd connected all the cables from the mac DVI output to the tv RCA input (the yellow one), nothing seemed to appear on the tv screen. Clicking on "detect displays" in the displays preferences does change the resolution of the computer screen, but I couldn't figure out how to get the tv to display it.

I'm not sure what I'm doing wrong, any ideas?