You can try to carefully turn the turntable drive coupling in the bottom of your unit. If it spins quite easily, your coupling is probably broken. If it doesn't turn easily, do not force it, you could break the coupling if you try to turn it too hard. If it doesn't turn easily, you could have a bad turntable drive motor. Typicaly they are mounted in the bottom of the unit installed from underneath.
James Bennett / A. C. & M. Service, May 2007