the two small belts that drive the rim drive can produce squeaks. if you disconnect the rim from the platter and still hear the squeak, it's coming from the two smaller belts. clean the pulley of the motor well, that should eliminate the squeak.
if problem persists and squeak is not coming from motor belts, make sure the rim drive belt sits evenly in the groove. Mike suggest using a small pin or needle, carefully lift the belt off the rim drive and insert the pin in between belt and the metal rim, run it around the whole rim a few times, and pull the pin out. this should ensure rim drive belt sits evenly w/o bumps or twists.
if problem persists and squeak is not coming from motor belts, make sure the rim drive belt sits evenly in the groove. Mike suggest using a small pin or needle, carefully lift the belt off the rim drive and insert the pin in between belt and the metal rim, run it around the whole rim a few times, and pull the pin out. this should ensure rim drive belt sits evenly w/o bumps or twists.