Micky wrote:

$200? Did you order from an appliance supply instead of from
MCM Electronics, Dalbani, Premium Parts, etc? It's possible you
could have bought another small microwave oven and taken parts
from it because many magnetrons are identical. The mechanical
fit of the magnetron must be exactly the same or strong
microwaves can leak where the magnetron seals against the
chassis.
How many microwave ovens should I have bought before I found the
one that fits properly?

2, from stores that are good about returns, in case you got the
wrong parts. I would have checked the UL registration number
to improve the odds of getting something that uses similar parts.

So you would take the microwave apart, and if it didn't match, return
it? No store is that good about repairs.

The whole idea of buying microwaves and taking them apart to find the
right parts is totally asinine.