Ulysses wrote:
Hi everyone. I read many web sites about testing and repairing
microwave ovens and have concluded that my Sharp microwave has a bad
diode and capacitor. I checked the magnetron and, according to what
I read, it's probably OK as I get a reading of about .4 ohms across
the terminals and it is not shorted to the case. However, I'm
wondering if it is possible to test the magnetron with low voltage
DC. I assume that what is usually fed into it is 120 VAC rectified
which I think will result in about 170 VDC. If that's the case, then
could 12 VDC be used just to verify the magnetron still works before
spending money on other parts? I ain't gonna do nothin' 'les someone
says it's OK and explains how ;-) The sympton right now is that it
buzzes and blows the fuse so I'm thinking an open diode and shorted
capacitor results in feeding 60 Hz AC to the magnetron thus causing
the buzz. Does that sound right?

Not even remotely close. Magnetrons work at around five thousand volts
after the doubler circuit; I don't know where you got the 170VDC figure
from.

Read Sam's guide and then ask over at sci.electronics.repair to get some
advice from guys that do this every day.

Sam's guide: http://www.repairfaq.org/sam/micfaq.htm

Note: Cautions about killing yourself by mucking around inside of a
microwave oven are neither unfounded nor exaggerated.

Jon