GE Microwave Troubles SCA1000HBB04

More great advice from Kelly on the Appliance Zone Repair Forum!

Question: I have a GE Profile over the stove combination microwave/conventional oven, model SCA1000HBB04. It ran fine for a couple of years but started making a humming/buzzing noise if the door was shut even if no actions were selected. I tested it by putting in a mug with 1 cup of water, shutting the door and setting the timer for 2 minutes. I did not select either the microwave or conventional oven settings but the water was boiling by the end of the 2 minutes. The microwave has since been unplugged. The happens each time I plug in the microwave though for a couple of months it would work normally when plugged back in. Now it always hums/buzzes if plugged in.
Other symptoms/conditions:
-turntable does not turn when heating like this,
-light does not come on when heating like this,
-both turntable and light appear to work normally if I turn on the microwave to heat normally though it only appears to heat on high (100% power) regardless of the power setting I chose,
-the door must be closed for the humming/buzzing to start.
Any ideas?
Answer from Kelly Smith on the Appliance Zone Repair Forum: Hi, sorry to hear of your microwave trouble. The Smart Board has a relay that powers the magnetron. That relay has a set of contacts in it that have become welded together. The Smart Board, number 1655 in the diagram, will need to be replaced.


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