How to use s-video port to use it as display in Beagle Board Rev C4


I am using beagle board rev c4. When I try to use s-video port for
display using s-video cable connected to my T.V, my flash gets
corrupted. I have changed boot args to use s-video as display setenv
defaultdisplay=tv and still my problem didn't get solved. Can some one
explain me the clear procedure to use s-video port as my default
display and make it work.