How to Troubleshoot & Replace Lg AP4437489 / 2B71165R Microwave Magnetron

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 

I replaced the magnetron. Being a past service technician, I had the experience and basically the ear to know that the magnetron was not working. Now, it works like the day it was purchased. 

I replaced the Magnetron--wow, what a difference. It seems to work better than it ever did! 

After checking all of the high voltage components and having them check ok, I figured the magnetron likely was bad even though it checked good with electrically. After replacing it, the microwave worked great. I'm returning the unused parts. 

Took it apart found the drawing in it did all the test with a ohm meter found the magnetron was bad order the part put it in and know it's working find. Got good help went I call got the part real fast Thank for all the help .will use them again 

I replaced the magnetron. It was simple and quick. 

I had continuity between one of the terminals and the body of the magnetron. Replaced it and it works great 

Purchased and installed a new magnetron. 

Removed casing and replaced old Magnetron with a new one. 

Replaced the magnetron and capacitor.