TV has begun showing patches of a

Your picture tube has been magnetised. Now the TV has got an internal degaussing (demagnetising) coil that is supposed to demagnetise the picture tube every time that you switch on your TV. So it is possible that this circuit has failed in which case you need the repairman to look at it.
In most cases however it is caused by the presence of strong magnetic fields near the TV. Look in the vicinity of the TV and remove any strong magnetic fields. these could be loudspeakers, devices with electric motors or simply magnets.
Hope this helps.