Starting to poke through the innards, the hood tco is open circuit.
This should be less than an ohm??
And could this be the cause though it is not part of the H.V. components?

Edit 10 hours later:
Seems there are 4 TCOs and maybe the hood tco is the only one that is supposed to be open at room temp and close at some higher temp?

H.V. diode reads open both ways on my meter, maybe meter is a cheap one.
I put the diode in series with meter in Vac mode and ran house ac (120) through it. the meter read 66.7

The capacitor resistance runs up to OL (infinity) in about a second. each lead is infinity to case.

magnetron leads (filament leads?) read 0.7 ohm and each are infinity to case.