Ok I have a 43H70 Toshiba that is four years old. We have been experencing the same problem since 2002 with the convergence jumping. If you were a tv repair center what would be the first thing you would look at on the tv?
I am not a repair person but I do know one of the things they would ask."Does the picture/screen have an hour glass apperance"? This happened to my 52" RCA and the repair guy replaced the regulater - part: STK730-130, on the convergence power board and it worked perfect for a little over a year and now I am having the same problem. Maybe this will at least get you started on what to look for... Good Luck...