A friend owns a bush tv, recently the colour in all four corners has turned blue. The blue is darkest in the corners and gets lighter closer to the center of the screen, which has a round space where the colour is normal. Red does not show up at all, and comes up green on screen. Brushing a magnet over the screen resolves the problem temporarily, but for a second (literally). thank you for your help

Mike Kane, July 2004

posistor has gone in power supply

chris jones tel 07981308065, June 2008

The screen is magnetised. Usually, severe purity errors as you've described are very simply repaired by replacement of the 'Positor'. It is very simple and inexpensive repair. Placing an ordinary magnet over the screen simply moves the magnetised area and likely to cause permanent damage to the shadowmask. A service engineer will have an electro-magnet specially designed to remove any magnetism.

Cobweb, September 2004