If you can remove the back cover, see if there is an orange glow inside the
neck of the picture tube. You may need to turn out the room lights to see
this. If you can see it, then the problem may be as simple as bad solder
joints on the socket on the circuit board that plugs into the back of the
tube. This board usually has a metal shield soldered to it, making looking
for bad solder joints a bit tougher. But this is a common problem.