have you installed the nvidia driver?
you should install it first and then edit the /etc/XF86Config-4 file:
also read the README file, it has a whole paragraph on TV-OUT.
Option "TwinViewOrientation" "Clone"
Option "ConnectedMonitor" "CRT,TV"
try these first, then
Option "SecondMonitorVertSync" "<fill in the range>"
Option "SecondMonitorHorizRefresh" "<fill in the range>"
but those aren't necessarily needed, but if your resolution is too high, you need to adapt resolution modes.
most TV can't display resolution greater than 800x600...
Alien is my name and headbiting is my game.