Electronics fail for a lot of reasons. Is it an older appliance? Parts can just wear out. What has the weather been like? A power surge could have fried some of the circuits.
Was there a power outage in your neighborhood? Is a fuse blown in your house or building? Did you accidentally step on a power strip which was connected to your television? If none of these scenarios are the case then you may have an electronic problem with the television itself.
It is hard to diagnose without more details. It could be old, and tubes burnt, you could have suffered a power surge, blown a breaker, or it is defective.
