Help Problem TV

[gregory]

I have a Paqnasonic Colour TV Model TC 29V26A and no circuit digram.
The problem is when the TV is turned on the Picture starts to come in on the sides only a small amount then stays there.
When the volume is increased the picture jumps in and out about 100mm on both sides.
When the volume is turned down it returns to a small amount on both sides
I have replaced all the caps in the power supply but this has not repaired the problem.
Help