PIC16F628A blank composite video test

Hi all a few month ago I stumbled across this site
http://www.rickard.gunee.com/projects and was compeled to get into
microcontrollers and do something similar. Anyway so I bough a
PIC16F628A and JDM programmer. Now I am starting of simple so I made
this blank composite video test
http://home.aztec.aunz.com/dabski/VID_TEST.asm All it dose is create a
the syncs and leave the screen blank so that the TV can lock onto the
signal. Unfortunantly it dose not do this for some reason the TV dose
not detect the signal, when I run the program through a simulator with
an osciloscope eveything looks OK. Anyone go any ideas of what the
problem might be?

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