i would have thought the s-video out is directly related to the GPU and would have nothing to do with a tv tuner card??
Does it not work? it might be that although you have something plugged into it you still need to tell the laptop to project to it... eg on my IBM t42 when i have something plugged into the s-video i need to press 'function (Fn) + F7' which cycles through outputs....
the svideo is not working if you dont have the mini pci tvtuner?
Where did you get that from? You might be confusing s-video out and in. The pci tv tuner adds an s-video in port. Obviously this does not work without the tv tuner, but I've never had problems with the s-video out port.