Here at work our little Samsung microwave was cooking away and then just
quit. Upon investigating it, I find the fuse blown. Ok, then check the
door switches - all 3 ok. I have put a copy of the schematic at
http://www.kcswug.com/documents/SamsungMW21310.pdf .

If I replace the 15A fuse with a little larger one, it will come on but with
an abnormally loud hum. If I unplug the magnetron by pulling the wire from
the FA terminal, the excessive hum is still there, which to me means that
the magnetron isn't the cause of the problem here. If I lift the rectifier
ground, then the hum stops. The rectifier isn't shorted, but I also can't
test it with my Fluke meter as it reads open both directions. But the spec
sheet on the rectifier says it needs 14 volts to pass through it, and my
meter only has a 9 v battery. When I measure the cap, I get .2 ohms across
it, which tells me it is shorted unless there's something special about it
that I don't understand.

Sound reasonable?

WT