Old zenith intermittent power on problem

Question

I have an old Zenith tv, which I've had for about 15 or so years.  All of a sudden, when I plug it in (the switch has been broken for about a year), it would not come on, no sound, picture, nothing.  Now, it comes on about once every week or tow, it works perfectly.  The rest of the time, either it makes a sound, but no picture or it makes no sound and no light on the screen whatsoever.  What could it be?  Is it worth fixing?ThanksPam