We have a GE microwave which I would guess is 10 years old. It is built-in and was here when we bought the house. Worked for fine for 3+ years. Now when we use it, it makes a rumbling noise and the smell of burnt rubber is present. We have stopped using it. I think there is something wrong with the radiating element. Thoughts? If it is, can we replace it or do we have to buy a new microwave? Thank you!