No Picture but have sound. The TV is 6 years old. One day we switched it on and there was no

Question

The TV is 6 years old. One day we switched it on and there was no picture but we could hear the sound. When we switch it off there is a horizontal white bar that flashes on the screen for a second. I would like to fix it as the TV has been great so far.Please help!No picture but can hear sound