I have a old panasonic TC-20L3A TV and whenever switch on display picture shaking and making a heising sound.Please its my greatgrandfather's. How to repair it

Unfortunately it is very difficult to tell you on a forum how to repair a TV. You're best bet if you really want the TV repaired is to take it to a TV repair technician. If you risk trying to fix it yourself, you may cause more damage than was originally there.