Microwave stopped heating. Tested all components in the high voltage circuit. All tested good. But no heat. Replaced Magnetron with a good used one and the microwave now heats. Ordered and installed a new Magnetron and no heat. Reinstalled the used one and now it heats again. So, is the new Magnetron no good? This is an LG microwave and it is 4.5 years old. Purchased 1-9-10. Whydoes it work with the old used one but not the new one? 
Magnetron part #
Magnetron
by LG
Part #: 2B71165R (AP4437489)