Spin Doctor #40: Turntable Drive Mechanisms & the Esoteric T1 turntable
Making a turntable's platter spin at exactly 331/3 rotations per minute sounds like it should be an easy task, but in fact it's hard to do precisely. Just getting the platter to turn is easy enough, but there are two forces trying to stop the platter that you need to overcome: friction from the bearing that supports the platter, and friction from the stylus riding in the groove.