Zenith shuts off
 

I'm having trouble with my old 27" Zenith Sentry 2. It will suddenly
shut off. Often this is accompanied by a low whistling sound.
Sometimes it can be switched right back on, But often it will often
take a number of attempts. Each attempte results in a click and a
flicker of light. This state can last for several minutes. More
recently it will not respond at all, either to the remote or the on/
off switch on the set itself. However, if I leave for 10 to 15 minutes
it recovers. If I can keep it going for an hour or so, the problem
will sometimes clear up. The picture an sound are fine, and all the
other functions work properly. Can somebody give me an idea what the
problem is, and whether it's worth fixing? Thanks in advance.

Zenith shuts off