The carbon brushes are on the motor of the machine - they remain stationary and deliver electrical power to the rotating part of the motor. Like a pencil they wear out over time and if left too long the motor gets hot and smelly, sparks fly and you get strange noises.
Here's a youtube vid link about changing Carbon Brushes...
http://www.youtube.com/watch?v=0GmtRBiXLFc&feature=PlayList&p=F82654651FCE7539&index=0&playnext=1
Good luck...
Peccavi, May 2009
