Started with the diode, didn't help. Installed the Magnetron and we have a working microwave again. Just cleared the transformer on removal.
While the unit was down I thought I would give it a good cleaning. Lots of grease in the blower assy.
Very fragile plastic blades, broke two blades (now out of balance and made a terrible vibration noise) and had to go to E-Bay for a $20.00 used replacement.