My 4.5 year old GE Microwave PT970M1BB Buzzes Loudly when the door is shut. This microwave is built-in with an Oven below.

Loud buzzing starts immediately when the door is shut.

So far, I have replaced the Transformer, Magenetron & a plastic "Air-Cover" (basically a duct that goes between the Magenetron & the side wall of the microwave cooking chamber).

The original "Air Cover" was melted on top so I assumed the Magnetron was overheating causing this problem.

I just completed the replacement of all these parts and when I shut the
door the buzzing starts and I see some "whisps" of smoke coming up from the magenetron. I am not sure if this is just because it is new and needs to break in a little and burn off some paint or if this is another symptom of the real problem.

I called one of the sales folks and they looked up my problem and said that other Posts have indicated either a bad door switch or the control board for the microwave.

Hopefully this will be a relatively cheap-fix since I have already sunk alot of money and time into this unit.

Thanks for your help.

Bill

I ended up replacing the Control Board and all was OK after that.

Check your Air Duct and make sure it is not melted - If it is, I would recommend replacing it while you have the unit torn apart.

Good Luck

Bill