I have a GE XL1800 spacemaker microwave. I began making a humming noise (louder than usual) when cooking. After a week or two, it stopped heating. All of the other features work fine. After reading your forum, I decided to replace the magnetron. I took the old one off and saw that it had a burn hole (apart from the regular hole) in the end. The first mag GE sent did not heat and made the humming soud again. I had GE send me another one and I installed it. It sounds fine but still no heat. I rechecked all of the other features and they still work. I can hear the power cycling on and off in the defrost mode. I checked the connections, wires etc. and it looks ok. Anything else I might be missing? Thanx in advance.

Hey Applianceman,
Thanks for the info. After reading other posts, I was thinking the diode could be bad as well. I gave it a visual inspection and there was no burned marks, cracking or anything else I could see on the diode exterior. I wanted an expert opinion before I changed it out. Let's hope that's it or it's the landfill for this thing. Thanks again.

JetFla