Ken S Cumberland , RI February 24, 2015 Appliance: Frigidaire Microwave Hood Combo FPMV189KFB Microwave making loud humming noise We had a problem with the magnetron a few years ago while it was still under warranty so they sent me a new magnetron but when the repairman showed up he had a new one also and said just keep it as a spare (no charge). It's an over-the-range microwave so taking it down takes a little bit of an effort, cumbersome more than anything. Got it down to my work bench, took off the housing, checked to make sure the capacitor was discharged, removed the capacitor (diode is attached to it) and transformer. Then replaced the magnetron and put everything, minus the housing, back together. No luck still making a loud humming noise. Searching on line I found that a faulty diode/rectifier could be the problem. I ordered it from ApplianceParts on a Friday afternoon asked for 2-5 day delivery but was surprised to find it in my mailbox the next day. Put the new diode in and it works like a charm. Read More... 12 People found this story helpful Do-It-Yourself Rating: Repair Time Estimate: 2+ hours Tools: Pliers, Screwdrivers