It was pretty obvious the magnetron had to be the problem. The microwave sounded like it was working, but the food wasn't cooking. Since the magnetron is the source of the microwave energy, it had to be the problem. This was on a GE Profile microwave oven. Pulled the screws off the outer cover. The cover then slides into a mating piece of sheet metal at the front of the machine so you have to slide it towards the back to get the cover loose and remove it. You can then easily see the magnetron on the right side of the machine. There's a plastic diverter attached to it with one screw that diverts the fan air flow over the cooling coils of the magnetron. Remove it. Unplug the power connector on the bottom of the magnetron. Remove 3 screws holding the magnetron in place. The magnetron is now hanging on 2 metal hooks at the top so tip the bottom up and pull up and out as you remove it from these hooks and set it aside. Hang the new magnetron on these hooks and secure it with the 3 screws. Don't forget to reinstall the air diverter and reattach the power connector to the bottom of the magnetron. Lay the oven top cover on top of the oven pulled back slightly from the front, align it and slide it forward so that it reengages the sheet metal on the front. Put the screws back in and you're done. Please note: the screws along the back are torx, but they have a small island in the center of them so a normal torx won't fit. You can break this off with a small screwdriver, use a small screwdriver to take them off or use a torx with the appropriate hole drilled into the middle of it.