The likely problem with the turntable is a bad turntable motor. If your microwave is JE1860WH, the motor is part 6549W1S017A, and is available here: http://www.appliancefactoryparts.com/search/part/312564/126487 . Other parts for the microwave is http://www.appliancefactoryparts.com/microwaves/ge/je1860wh.html .
Unfortunately, I do not know of any source for this model.
I hope the parts source will help with your current microwave problem.
Answers & Comments
The likely problem with the turntable is a bad turntable motor. If your microwave is JE1860WH, the motor is part 6549W1S017A, and is available here: http://www.appliancefactoryparts.com/search/part/312564/126487 . Other parts for the microwave is http://www.appliancefactoryparts.com/microwaves/ge/je1860wh.html .
Unfortunately, I do not know of any source for this model.
I hope the parts source will help with your current microwave problem.
Cindy Wells