Here's a way to test the HV diodes in a microwave. Don't kill yourself.
I'm not sure if 6 volts would work with a color TV HV diode since they
go up over 35,000 volts
That site reads, in part,
"Testing the HV diode requires an ohm meter with at least a 6 volt
battery in order to accurately measure the front to back resistance of
the diode. Meters with insufficient battery power may read infinite
resistance (open) in each direction, mistakenly showing a good diode
as being open."
It also reads;
"IMPORTANT SAFETY INFORMATION: Microwave ovens are among the most
dangerous appliances to work on. Before attempting any
troubleshooting, testing or repairs, for your personal safety, we
strongly urge you to carefully read the very important safety
precautions found by clicking here and Please read our disclaimer at
the bottom of this page.
Please be very careful. A microwave oven is essentially a 1000 watt
transmitter in a metal box. With DC voltages up to 5000 volts at
amperage that can easily kill. Also microwave radiation at wavelength
of about 13 centimetres (approx. 5 inches) that can cook meat,
including you. And fry human eyeballs .............. cataracts anyone!
More often we have found defective door micro-switches and faulty over-
heat devices and or the magnetrons themsleves are reason for not
working. Yesterday saw microwaves for sale in super market for $49!
Hope this helps.
On Fri, 15 Jan 2010 21:42:08 -0500, "badgolferman"
Probably not. When my Amana model 2 Radarrange broke, about 20 years
ago the parts woman suggested it was the microwave tube, about 250
dollars. When I called again, she (another she) suggested it was the
diodes, about 125 dollars. When I actually took the thing apart, the
insulation to the diodes was crumbling, and if I couldn't see arcing,
I knew there had been some. This was the second model ever made and
pretty old. I used some GE silicone to insulate it. I figured if
they make glass out of silicon, the GE silicone must have a high
That worked for another 5 years and then the transformer went out.
Again they wanted 375 but said he would give me the wholesale price of
250, dollars, for a replacement transformer. I said to him, you know
I'm the last guy in America who's going to try to fix one of these?
You know you can buy a new one that's nicer for about 100? Sell it to
me for 50 so you can make a little money from your leftover parts.
He told me to write Iowa. I liked my prototype model, that looked
just like the ones in history books, so I did. I told them to save
6 for their museum and the family of the inventor and owners, to keep
theirs working, and sell the rest for what they could get. They wrote
back and said to call a number in Pennsylvania. I called and it was
like starting over again. He still wanted 250
See: http://www.repairfaq.org/REPAIR/F_appfaq.html for good
information on uwaves. You can probably find a wiring diagram on the
inside of the metal uwave cover. Remove screws along the back and
bottom to get the cover off. Read the FAQ carefully about electrical
hazards. Then report here what you find and we can probably walk you
thru some fairly simple checks. Do you have a voltmeter?
Okay, I have done more troubleshooting of the microwave. There are
three interlock switches on the door and they all open and close
properly. There is a secondary interlock relay on the circuit board
that 115 VAC is getting through. That is directly connected to the
primary windings of the transformer and when I took both leads of the
transformer I read the 115 VAC on the White & Black wires. Ohms
checking of the primary and secondary windings are lower than what the
schematic shows which are 49 and 89 ohms respectively, more like 20
ohms or so. The high voltage diode cannot be read either way and a
replacement that someone gave me from their old oven reads the same
way. I tried that one out and still get no heat. I put my multimeter
on the capacitor on its highest ohms scale and get a wavering reading.
I do not think the interlocks or the diode are bad. The transformer
and the capacitor are probably good but I defer to the experts here. I
do not know how to check the magnetron. There are two round black
components inline with the power that I assume are the flame and gas
sensors. My guess is they are good since power is getting all the way
to the transformer.
Any more ideas?
It's what I thought at the time. I still don't know what the
But it worked. I've successfully used GE silicone** for the micowave,
and for a color tv flyback transformer where the voltage is about
30,000 iirc. (The second time I had to put on several layers. Each
layer would move the spark somewhere else, and the final one stopped
**(sealer or cement?)
There is no relationship between the two except they are both found on
planet earth and they are spelled very similar. Silicone is man made
and silicon is natural (I think silicon is the second most common
element on earth). Seriously, it's about the same as comparing
toothpaste to granite.
Glad it worked for you. I used it once on an old video game monitor to
fix a high voltage leak also, (although I gave the guy no warranty and
told him it was patched up, not fixed.) Careful with that high voltage,
it does go that high, actually higher. Get zapped enough times and you
may end up like me and you know you wouldn't like that! And the picture
tube holds a charge like a big capacitor. Some will stay charged up for
There's no silicon in silicone!!! I feel as if I caught my wife
cheating on me. Sure, she never said she woudln't, but I assumed it.
Whew, you had me scared, but silicon is an essential ingredient in
silicones. As well as H, C, and O, and other things like Cl at
What are you like?
Yeah, I know about all that stuff, but thanks for the warning. If I
have to touch a CRT, I'm careful to discharge it first.
I did get what I think was a 2000 volt shock once. I don't know how.
I was being careful. I didn't fall over or anything. I think my other
hand was 3 feet away. Either fear or the shock itself sent me
falling 6 feet back and I dislocated my shoulder for the first time in
about 10 years.** Then it came out a lot, within a year there was a
4-day period that it came out 3 times. But I had already started
looking for a doctor, and a month later I had it fixed and it hasn't
been out in 32 years. I can't sleep on my belly with my arm over my
head anymore, though.
So I too am trying hard to avoid a shock. I don't touch anything
when I put the silicone on, let it dry for a day, and don't touch
anything when the tv is on.
**(I had dislocated it about 8 times prior to that, but then I got a
job that required hard work, and I guess my increased muscle tone held
my arm in place.)
On Fri, 15 Jan 2010 17:38:17 -0500, "badgolferman"
When I wanted a wiring diagram from Amana, I had to beg the woman and
promise up and down that I knew what I was doing and wouldn't kill
myself. It's bad that everything else seems to work. It means the
problem is serious and probably beyond your or my skill.
Maybe someone replaced the Magnetron with a Cryrotron.
Sorry couldnt resist a bad joke.
Dead oven can be caused by a lot of things. There are numerous saftey
circuit and interlocks. One of the first things a tech would do is
bypass all of this and see i fit will come up. Should only be done by
a qualified tech. The circuit is very simple consisting of a very
simple power supply connected to a Magnetron. Everything else just
turns the power supply off/on. This doesnt mean it is easy to
troubleshoot and it is very unforgiving of stupid mistakes the
consequences of may be death.
Take the measurements of height, width, and depth. I'm sure that you can
find a new microwave with the same or slightly smaller dimensions.
I had a to replace an old cabinet MW with one slightly smaller. I put an
oak frame around it to hide the gaps.
"Everything seems to work
fine on it except for cooking" - what the heck else is there? A light? The
clock? My opinion is that if the oven doesn't cook, it really doesn't
matter what else does. Microwave ovens are generally not thought to be a
DYI kind of appliance. In today's world it probably could cost more to
repair than replace. Measure its size and head to Wal-Mart. They are bound
to have one almost exactly the same size.
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