My Sony CRT TV Model KV-M1420U has developed a problem. After 15 minutes
of perfect picture, the picture fades out by going through a colour change
to purple then totally black. All channels are affected. Switching off
for a few minutes recovers the picture but the situation repeats.

Anyone one got an idea where I should start to look for this thermal
problem? I am trained and familiar with working with high voltage and
electronic circuits but I'm not a T.V. engineer.

Beemer