I'm trying to connect my macbook to an old tube tv. When i connect with either a composite or s video cable, the picture just rolls down the screen in black and white. I read in a few places it has to do with the pal setting, but im in the US so i didnt think my tv was pal. I think i need to change the refresh rate to 50 hz, but I can't find any setting to do that or change the output to pal. Any ideas?