JVC TV AV-27230 picture doesn't lock in?

When I turn my TV on--and this has been for years, it doesn't lock in on the full picture. EX: I'll see 30% of the bottom...on the top and the remaining 70% on the bottom. Different percentages all the time. Rarely I get lucky and when I turn it on it is perfect. Sometimes I have to turn the TV on and off 30-40 times before it's the full picture. What the heck is going on and can I fix it myself?