I have a Sony model STR-DE675 that has done a nice job for about 4 years. Last weekend the TV sound went out, came back after about an hour, and went out again tonight. Just to test the system, I put in a DVD and got the same result--no sound. For the last six months, the receiver has been housed in a cabinet that has a four inch clearance on top of the receiver. Any thoughts on what the problem might be?