my Toshiba suddenly switches off?

It has a warm-up fault i.e. a fault condition that only appears as the set becomes warmer. It may be a poor joint (dry joint) or a component failing as it becomes warm/hot.

From what you say the fault may well be in the power supply area - but that's just a guess.

As a computer engineer in the 70s I used to use freezer spray to cool things down in an attempt to make faults like this go away - it sometimes worked. Another technique was to use a hair dryer to bring the fault on - less useful.

http://www.maplin.co.uk/images/full/n68an.jpg

Good luck...

Peccavi
May 2010