Sam

Took another look at the schematic--it shows a TRIAC in parallel with
relay boards power transformer. If the TRIAC were to fail that could
possibly lower the voltage to the relays on the relay board causing
them to open.

I'm unsure whether the control board is telling the relay board to
shutdown the magnetron--or if the relay controlling the power to the
magnetron is tripping off line (for example because of TRIAC failure)
causing the control board to think a manual stop has been issued from
the front panel.

Any thoughts?