I just want you to understand the risk involved with tinkering with a microwave, from the [http://www.repairfaq.org/sam/micfaq.htm|microwave troubleshooting]:
"'''Careless troubleshooting of a microwave oven can result in death or worse. Experienced technicians have met their maker as a result of a momentary lapse of judgement while testing an oven with the cover removed. Microwave ovens are without a doubt, the most deadly type of consumer electronic equipment in wide spread use.'''
Please be very careful if you remove any covers.