I have a LG under cabinet microwave LMVM2075SW that has stopped working. I think it is the magnetron. The timer works and counts down when started, the light turns on but nothing else happens. Can someone please help with any other possible causes for it not working.
Thanks
Bwilly

Unfortunately, the only way to check all the systems is to remove the microwave and take off the case. There are fuses and other safety devices in there along with a BIG capacitor that can shock you. Consider the age of your unit and realize that you will probably pay as much for repair as a new one. How old? More then 5 years, replace.

If you plan on doing this yourself, best learn and YouTube is great for learning. Safety first since electricity will kill you.

Most old stuff is expensive to fix even for an expert, and easier to replace

Microwaves are doubly dangerous for a neophyte to work on... because of the dangers they don't know about. And the ones that are invisible. (Not just electricity but ionizing radiation.

As was mentioned.. parts if you can find them are likely to be at least almost as much as a new unit... and could easily exceed the price of a new one... and while it might be fixed... it might be fixed for a few hours... days, months or if REALLY lucky years. You just won't know. That's why the smart money is on replacing an older appliance that needs expensive parts.

Took repairing a few different Appliances only to have something else fail shortly after to understand the logic and the cost savings of doing it that way.

But if troubleshooting by guessing..expect to be replacing good parts until you find the one that did fail. Given the number of components...odds are against guessing right the first time. And electrical components are almost always, non-returnable.