A conventional TV screen has a degaussing coil around the outside to get rid of any magnetism - switching on and off several times might do it but if your degaussing coil is defective for some reason you can place your TV face-to-face with a similar conventional machine and switch the other one on and off - your dodgy TV does not have to be on at the time.
The circles may have been put there by somebody playing with a strong magnet - great fun - I've done it
Good luck...
Peccavi, November 2009
