I have been battling with my TC470 for months :-)
It might be the fan itself, I replaced mine as it wasn't rotating smoothly and making a racket. I'm afraid it wasn't much less than £30.
There is a little felt rectangular spacer on mine that looks like it is supposed to keep belt from rubbing at the middle of the figure of 8. Of course the belt wears a groove in this so it becomes less effective in time. If this could be improved or replaced it could help the belts last longer (they do seem to stretch).
Mine whistles (slips on the pulley) particularly at the changes of direction, and I haven't solved this even with a new belt.
You might also check that the pulley wheel on the motor axle is running true - difficult to know how to fix it if it isn't, but I suppose it might be caused by uneven running on the main belt.
You can search for TC470 on this forum, or look at other ideas
(e.g. replacing fan/belt assembly with a motor kit) at http://www.ezee-fix.co.uk)
Good Luck.
BobG, July 2004