Goodmans Widescreen - crackling then picture goes off?

My Goodmans widescreen TV is about 5 years old. A few minutes after switching it on there is a crackling sound for a while and then the picture goes off.
Any ideas what the problem may be?
I have had the back off and there is nothing obviously loose. The only difference between it working and the problem is that it was moved to the garage for a few days (April 2004) while the room was decorated.