Samsung 40" TV LE40R88BD - turns on but no picture and hissing sound?

My Samsung tv is about 2 years old now, probably slightly older, it was working perfectly fine last night, but this morning turned it on, and there is a slight hissing sound coming from the top left side of the tv and no picture at all, when you change the tv source, to either Sky or for the PS3, the screen changes as normal but still no picture at all no words etc., any help greatly appreciated