The guy came over today, boy he really wants that old box fixed! I was able to find a place online called fixitnow.com that had a bitmap copy of a page from a repair manual for this model. It had tests for the magnetron, high voltage transformer, capacitor, and hv diode. The magnetron tested good, the transformer primary winding spot on, secondary winding not enough resistance, filament winding no good. Capacitor tested bad, you know a cap is supposed to jump up then go back on the ohmmeter, didn't do that at all. Diode tested bad. So this is already up to about $250 in overpriced parts, and I can't guarantee anything.
I have to convince the guy this is gambling with a smelly, dusty old bomb.
On top of that, if I want to post questions on this fixitnow.com forum, which has a "Samurai" theme, I have to pass a technician's test!!! I gave it a try but I'm not really up on the basic electricity questions!
Maybe this microwave took a power surge, no telling what else is going on with it. It's a convection oven too.
I think he's worried about the hassle of a new unit; this one is outside vented and has a big mounting plate over their stove.