TVs with a regular picture tube have a de-magnetising coil around the tube - close to the back edge. Each time you switch on / off the tube gets a de-gaussing from the coil.
I know this - I foolishly put a very powerful magnet up to a colour screen and watched the colours change - fascinating!
Not so good when you take the magnet away and the colours stay messed up! A couple of power cycles soon had it back to normal.
Peccavi, December 2008
