Philips tv 28pw

[russandnit]

Hi can anybody help???
I have a philips 28" widescreen tv and all works fine apart from video and dvd.
If i plug the freeview in on scart lead all works fine but if i put the scart into dvd or video all i get is sound and no picture.
the picture will flash up when i first go onto ext channel but then dissapears and just have sound???

Does anyone know what this fault is and can it be rectified??

Russ