60sx12b/13k black screen

I turn on the tv and after about 5 minutes the screen goes black, but the sound is fine. I turn off the set and the picture comes back on and it will repeat to black aftera couple of minutes. I have sound but NO picture at all. When I do the "magic focus" adjustment I get the red, green and blue lights. (individually) The closed caption text is visible but it appears to be a bluish hue. I was watching it and I left the room, came back and this is what I had.