What has possibly happened is that the tube has become magnetized due either to loudspeakers or any other device containing powerful magnets near the tv screen or that the degaussing posistor, a component hat requires replacement the cost of which is very cheap.
This device when you switch the tv on from cold passes a large current thought the degaussing coils around the tube to demagnetize the screen, this posistor suddenly heats up and this action causes a reduction of current through the coil after a few seconds or so after switch on.... these posistors run quite warm and is a common fault that causes coloured blotches, pink grass and purple faces etc.
Do make sure there are no hi fi speakers near the tv though, if the sets been on you need to switch it off for a couple of hours to let the device cool down before switching on again otherwise it ian't gonna do it's job properly.
David, June 2008
