I have a 331 and really love it! I have recently experienced the same problem with the right channel. It cuts out after it's running awhile, though it continues to play faintly. A year and half ago I a local shop replaced the Output I.C. and to be honest I don't even know what does. I'm really have no electrical experience or know my way around the inside of this receiver. Just a music lover. When I originally bought it, one of the channels (pretty sure the left) produced no sound, hence that repair.
At this point I have just a bit over $100 dollars into this receiver and while I love it, I don't want to put much more into it. Is changing the caps something a complete novice like myself should even considering attempting to do? I'm using a Kenwood KA-52 (only other amp I have) in the meantime, which is pretty solid, but I prefer the sound of the Sansui.