Aren't all Amigas 15Khz PAL/NTSC by default and you have to tell them otherwise?
It should be as simple as selecting PAL:High Res Laced in the ScreenMode Preferences and just using the video/composite ports.
Does an A4000 have an RF modulator as standard?
EDIT: Hang about, if you're already running on a TV you must be in a PAL/NTSC mode already?
