Hello, my tv is saying no signal & won't let me select the av channel like usual...?

[jules]

It was working fine last till yesterday....It is a Phillips flat screen about 2 years old & was working fine till yesterday. I have sky which is working as I can get tv upstairs through my wireless sender, though the picture went & i was left with just sound after a couple of hours. I have never had an outside ariel just the sky dish...I have checked all wires & unplugged for a while etc & unplugged sender too....any ideas anyone?? I'm baffled