The turntable in this combo microwave/convection oven stopped revolving. I didn't notice any early signs of a problem (like sporadic or start-stop revolutions) -- it just occurred suddenly.

I've been looking through other posts here to try and diagnose the issue. There's nothing obviously wrong that I can see with the coupler drives the glass turntable itself. I haven't tried pulling the coupler off to check for cracks, though -- the coupler doesn't easily lift off the base and I didn't want to force it.

Is there a way I can eliminate other potential causes before I try replacing the turntable motor?

Thanks, Jack