[Username1]

Hi! RCA XL100 tubes were driven pretty hard, and they show signs of age pretty quick... Usually in the form of a trailing streak of color next to a dark item on the screen.... It would be nice if you could post a few pictures of what you are seeing, it may be something other than the tube.... The color streaking in the aging tubes usually gets worse as the brightness is increased, less as its made a little darker....

Picture tubes generally last longer if they are not used as a spot light. Watch tv in a less than brightly lit room, don't make the tv compete with the sunlight, and keep the contrast low as well, and the tube will last a very long time. I believe that is true for all picture tubes, newer and older.

On time hours have an impact as well.... If the set was used as a spotlight for 19 hours a day, then expect to see a weaker tube there too.

The top of the scan becoming visible could mean at least one capacitor beginning to go bad in some way, if it continues to get worse you may need to do some work..... If its temporary then it may just be a minor voltage fluctuation either in your neighborhood, or the tv. Does your home have a big A/C unit running? or on the same circuit? Be sure its a problem before you go nuts trying to fix it....
Good day.