Answer to: Can I repair my - noisy but cold - microwave oven?If you hear a very loud buzzing, it is probably a shorted high-voltge diode. This may be a small black stick wired to the high-voltage capacitor (metal can with two terminals), or could be inside the can. You would have to replace it. I doubt if the magnetron is bad, they are very reliable and last a long time. I designed microwave ovens for 30 years.