On Jul 3, 6:29*pm, Chief Two Eagles wrote:
On Sat, 03 Jul 2010 15:20:18 -0700, 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?

Thanks.

Sounds right to me. If you replace the cap and diode why not do the mag
too? They sag in output as they age so if you like the oven you have do
it justice and replace all three components. Just make sure you don't
handle the leads on the capacitor. It can store a nasty jolt. And you
probably have a shorted diode if it blows the fuse.

"Just make sure you don't handle the leads on the capacitor."

I don't know what size caps are in a MW, but I used to work on
transmitters that had high-voltage oil filled capacitors, like
this...and bigger:

http://www.recycledgoods.com/product...51850_zoom.jpg

If you didn't put shorting straps across the taps as soon as you
removed them from the equipment they would charge up to 5KV or more
just sitting on the workbench in the transmitter building.

We used to use a hi-pot and a dead-man stick to show the newbies why
they should stay out of the transmitter building unless they were
accompanied by a journeyman tech. We'd hook the grounding strap of a
dead-man stick to one tap, charge the cap up to 2 or 3 KV and then
touch the hook of the dead-man stick to the other tap.

The resulting arc and *crack* would scare the crap out of the newbies.
One time we charged the cap up too much and it blew the threaded rod
of the dead-man stick right out of the handle. That one scared even us
seasoned techs!