Sounds a lot like a cold solder joint to me or some copmonent going bad that is heat related.
About a year ago I found this big RP crt TV sitting on the sidewalk in front of someone's house. I knocked on their door and asked if it was junk. They said something about the image becoming narrow and thought it was a bad CRT. They figured it was a few hundred bucks to have it fixed, so it was up for grabs.
I took it home and figured it was something in the horizontal sweep control. I bought the service manual for the TV for $35 and that included the full schematics. I traced it down to a cold solder joint on a three terminal voltage regulator which I reflowed.
There's a great forum for TV repair and I suggest you pose your question there. There seem to be a lot of techs on there who know a lot about these things..
http://www.network54.com/Forum/185128If you do a search for your make and model of TV I'm sure you can find a place that will sell you one cheap.
-Tony
edit: I'm sure you are already aware of this based on what you had in your post... but I'll say it anyway....
beware of the high voltages in these things. The capacitors in the power supplies store a gigantic charge and at high voltage. Chances are they have bleeder resistors but always treat them as if they don't. the power supplies in these can easily exceed 30kV and a lethal.