force svideo port to work with svideo to rca cable?

all,
so i don't have anymore viable svideo ports on my tv. before my new tv comes in, i'd still like to get the svideo port working on my IBM thinkpad t42 (ati mobile 9000).

when i use a straight svideo cable to an existing svideo port on my tv all works.

however when i use an svideo to rca cable the laptop thinks there is nothing connected and straight refuses to turn on the svideo port.

the crazy thing is that if get the svideo to svideo connection going and then plug in the svideo to rca cable, it stays working.

i've seen others reporting the same issue on other laptops (toshiba).

is there someway to force the laptop to turn it on?
alternatively there must be some hardware hack?

i'm thinking that the svideo cable just doesn't have two (or more) of the four (plus ground sheild) pins connected to anything so the laptop thinks there is nothing there.
any ideas as to what it needs on each pin? it's probably ground or power, but i have yet to figure that out.

any ideas?

here is a DIY cable:
http://www.diylive.net/index.php/2007/07/13/diy-s-video-to-rca-converter/
i might try that

thanks