How can I fix my Phillips TV?

I've had a Phillips 20" TV for a few years now and i've never had any problem with it. All of a sudden, it just stopped working. The standby light is on so I know there's power to it. When I do manage to get it to come on, it only does so for a couple of seconds and there is a white line running across the middle of the screen, and then it switches back onto standby again. Does anybody know what could be causing this problem?