My cabinet mounted microwave had two above mounting screws so I braced up my appliance and I unscrewed the two screws so I could take it apart. I removed the back plate and bottom plate and also the digital cover which only needs I believe pushing up and has no screws. It has plastic hook retainers. I have a Kenmore microwave which is nine years old but looks new and was told the problem is usually a fuse. The fuse was good besides the turntable and digital display was good so not the fuse. Shorted transformers make noise and mine was quiet so it was good. The big capacitor in the power supply looked good and rarely goes bad so I ruled it out. I reseated all power supply connectors and board connectors. No burnt spots on the control boards. A person on a video told me 99% of the time it's the Magnetron. Good enough for me and it was. The Magnetron at a glance looks like a transformer but it has two metal boxes attached together and it probably has magnetron written on it. I also checked the heat limiter earlier which was good; continuity in both directions. Make sure power is off when you work and avoid touching capacitors, transformers since they can hold dangerous voltages. I hope this helps someone. This was my first time working on a microwave but now I have a lots of confidence that I could track down the problem again. Good luck. Charles Mason