On 07/03/2010 05:29 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.
Speaking of capacitors holding a nasty jolt, when I was around 12 years
old my dear old drunken, worthless father, that liked to beat and starve
me, told me he was going to work on the TV and asked if I thought it
would be alright with the plug unplugged. I had heard that capacitors
help a charge even when something was unplugged, but I told him, it
should be alright. He jabbed a screwdriver in a flopped around for what
seemed like quite a while while I stood and watched. Afterward I said
"Well imagine that". The TV worked before he started and it worked after
he finished, so I don't know why he thought it needed to be worked on.

Another time he thought he would work on a light that didn't need to be
fixed, and he asked if it would be alright with the switch off or
should he turn off the breaker? I told him that as long as the switch
was off it should be fine. He stuck a screwdriver in there and was
practically doing a jig on the counter top. Again I said "Well Imagine
that". The light worked fine before he started and after.

I still laugh when I think of those times.
Old Geezer


And you
probably have a shorted diode if it blows the fuse.