This unit produces no mw output; everything else works.
I'm a consumer audio/video tech of 25+ years, so I know my way around HV, but I'm not a microwave specialist; hopefully you can draw from your case database for a more definitive verdict.

My tests so far:
1. verified cap and diode are good via Sencore bench equipment
2. between magnetron filament terminals: 0.7Ω; terminals to chassis: ∞
3. continuity on thermostats
4. leads of xformer (Zebra 19V4ZTT2); ∞ seen @ 20MΩ range:

• primary: 1.0Ω
  
• primary to chassis: ∞
  
• filament: 0.7Ω
  
• filament to primary: ∞
  
• filament to chassis: ∞
  
• capacitor: ∞
  
• filament to diode: 0.6Ω
  
• diode to chassis: ∞
  
• other cap lead to chassis: 100.4Ω
  
• ^ cap lead to filament leads: ∞

I have no schematic, so I don't know how this xformer multitap is rigged or if it has internal diodes, thermals, etc. I haven't tried ringing the xformer and I suspect my flyback ringer wouldn't be much use on these monsters anyway. I suppose I could scope it, though.

I have HV probes, of course, but I haven't checked the HV out on the xformer -- unless I'm mistaken, the rectified HV is negative with respect to GND (chassis). I'm not sure I want to risk my test gear on it -- though I also have an old VTVM which could probably handle it (maybe the multiplier probe could). The cap is definitely being charged (nice spark upon terminal discharge).

So, are these readings right for this xformer? Do you suspect an intermittent/thermal fault in the magnetron (Samsung OM75P(31)) or the xformer?


Thanks.

I finally got around to replacing the magnetron on this model.

The replacement restored function to the unit.

The new magnetron tested the same on my DMM as the original/bad one, which just goes to show that sometimes the only way to be sure is via substitution.