Gene: need advice on Amana ACO 1860 AW: not heating

Gene,

Please…I need your help. (Amana ACO 1860 AW 6 yrs old)
I fault traced everything, & everything specked out OK.
All values of all the pertinent parts were within spec. (as per service manual, & tech sheet behind control panel.

I replaced the diode, because I got a false negative on the original one, but the new one tests the same as the old one. (I rechecked them both with a 10V battery later, & instead of testing with an OHM meter…I checked current flow one way & the other…current flowed one way, but not the other)

So now my question is: some unknown part needs replacement…should I just replace the magnetron; even though it tests fine using the test procedures of the service manual & spec sheet?
It’s an expensive part to buy if that isn’t the problem for certain.

Please advise ASAP.
Thanks,

Al