Sylvia Else wrote:
This television displays a strange image and sound distortion just after
it's been turned on, as shown in this 5 second video.

http://www.youtube.com/watch?v=usQFxTJ04s4

It may do this several times, and, rather disconcertingly, seems to be
slowly getting worse.

Note - the slight flickering is an artefact of the video recording.

I'm using a computer output to show the fault, but I get the same
behaviour on broadcast channels if the computer is completely
disconnected, and turned off.

I suspect a warming up effect. Any ideas?

Sylvia.

Just a followup on this. The problem got gradually worse, to the point
where it continued for minutes after turn on.

Which gave me a chance to see where it was arcing. Turned out to be
underneath the circuit board, due to a fractured solder joint, and hence
only visible when I had the back of and bent down to see that area. Once
I knew where to look, it was obvious that the joint was broken. 30
second soldering job, and now it's good as new.

The surprise is more that it was working at all.

Special thanks to Jamie for the correct diagnosis of arcing.

Sylvia.