convergence is color convergence, as it sounds the red blue and green will not align.
this makes shit look like 80s 3d glasses movies.
Not really worth fixing on most tubes at this point
How big a tv w talking Jeff?
I mean you could upgrade to a sweet plasma in the 42-50" range right now for cheap..probably not much more than paying to have yours fixed.
problem you are going to run into is lamps have to be getting tired, sounds like vertical alignment is going out may be good money after bad.
For shits and grins take off the back panel, look and see if the lamps are loose or if anything is between the screen (obvious stuff)
i assume we are talking big rear projection here?