Jenn-Air Microwave turntable not working, microwave...

Hello. I have a Jenn-Air JMC8100AD built in microwave/oven unit in the kitchen. The microwave works just fine, but the turntable does not turn. When I lifted the glass plate, and turned it on, the little black plate holder turns when the microwave is on. So, it appears that the motor is fine. It is only when the glass plate is put on top of the little black holder that it does not turn. This suggests that the weight of the glass plate is too much. I suspect that it is some sort of coupling between the motor and the black holder. I have no idea how to remove the black holder. Any help would be welcome.