As Buttersoft has explained in the post he linked, you'll only only get a squished 480i picture from the TV-out on those cards. You won't get any proper video modes.
About 15 years ago, I had a similar video card (either an ATI 9250 or 9550, can't recall) and spent a awful lot of effort to get proper component video out of it.
TL;DR: The only way is via the RGB pins on the DVI/VGA port, using a special dongle (that should have come with the video card). You won't get anything decent from the actual s-video/component port.
To manage that, I had to use the Powerstrip software by Entech. It isn't supported anymore (since 2012), by you can still download it from here:
https://www.entechtaiwan.com/util/ps.shtmThere is a pinned writeup thread for Powerstrip on the monitor/Video branch of this forum. Only 13 years since the last post!
It wasn't easy to get Powerstrip working right. But when I did, the results were amazing, incomparable to component via TV-out.
With all this in mind, I decided there had to be an easier way. So I co-designed and built the GreenAntz RGB to component transcoder! You just install software (like CRT_emudriver), plug it into your computer, and your consumer component TV is like an RGB monitor. Just like that.
For more info about GreenAntz:
http://forum.arcadecontrols.com/index.php/topic,164245.0.html