It would be difficult for most people to measure the voltage while the
microwave is running. Not counting on any stray radiation,but at the
voltages in the microwave, it would burn out most meters. Also the high
voltage would most likely go through the insulation and into the person
doing the measuring.
Very few meters that are found are rated for much over 1000 volts, less than
half of what is used in many microwaves.
The ohmmeter in the common meters will not check the diode either. The
voltage drop across the diode in the microwave is more than the meter is set
up to measure in the ohms range. It is not around .7 volts as one would
find in the lower voltage diodes. Internally the diode is made up of
several diodes so the voltage drop is much more.
The ohmmeter in the common meters will not check the diode either. The volt
age drop across the diode in the microwave is more than the meter is set up
to measure in the ohms range. It is not around .7 volts as one would find
in the lower voltage diodes. Internally the diode is made up of several dio
des so the voltage drop is much more.
if the diode is good, with your symptoms i would next check the continuity
of the filament in the magnetron or look for a blown fuse someplace
DO THIS WITH THE POWER DISCONNECTED
Actually, I have worked on microwaves that
had a blown fuse. I put in a new fuse, and
powered up, and the new fuse blew. Turns out
the high voltage capacitor was shorted, and
had to buy another one. My parts house showed
them as no longer available. Ebay to the
rescue. Got one that was fairly close, and it
Christopher A. Young
Learn about Jesus
On 8/26/2013 10:21 AM, email@example.com wrote:
next check the continuity of the filament in the
magnetron or look for a blown fuse someplace
"microwave diode" can mean many things to me since I've experience in
electronics. The context in which it's being used in this thread is a
discussion of the high voltage diode used in the power supply for the
magnetron in a homeowner's microwave oven. ^_^
Sort of. A 9 volt battery isn't really a good test for a high voltage
recifier. The forward drop will exceed that of that battery, at least a
rated current of 0.3 to 0.5A, depending on the diode and oven.
The results of your test though, show the diode isn't open and isn't
shorted, so that's good. I'd not bother to replace the diode at this point
of the oven was in front of me.
I'd test the heater coil of the magnetron. It should measure close to dead
short ohms if it's good. If it's open, well, that explains why there's no
heat. You'd also want to make sure the transformer is even being turned
on, you can usually tell this from just listening to the oven or watching
lights flicker when the oven turns on.
Be sure you discarge the cap before you mess around in a microwave oven.
As mentioned in this thread by others, a normal volt meter cannot be
safely used to test the HV section of a microwave. You really don't even
need to for the most part either.
On Mon, 26 Aug 2013 04:18:18 +0000 (UTC), "Danny D."
Since apparently there is no current in that direction, how about
taking out the resistor and seeing what it says then?
Normally I'd say you should measure the voltages while it's in the
circuit. That's a little different here since you'd have to have the
cover off and that would expose you to a lot of microwaves. OTOH,
it's not working so maybe there are no microwaves. I hate to rely on
maybe. Do you have a microwave detector. I got one at Radio Shack
about 30 years ago and it works well. I was able to test it because
at that time I had Amana Model 2, and it didn't have door latches on
it. So I could open the door a little before the safety switches
turned the machine off, and I could see the detector reading rise from
zero to at least half way across the scale (but I only allowed that
for a second.) After that, I could check door leakage. RS doesn't
still sell them iirc but you might find one used, or you might find a
new one sold through another channel.
Here's exactly the same one I have, no bids yet, 18 hours left from my
post time. If it doesnt' sell he'll probably relist it so click
and a new one for only 15 including shipping
Here's one for more, $35 http://www.lessemf.com/mw-oven.html
I'm self-taught for the most part, but I would have just measured the
resistance directly with an ohmmeter, using the meter's internal
battery, in both directions. If one direction is many times higher
than the other, it's good. Even if I did it your way, I would do
it my way too, to see if the results confirmed each other.
For more info, ask on sci.electronics.repair
***I used to have an Amana Radarrange model 2. I never saw a model
1, but this one looked just like the image of a microwave everyone
used for years (except compeititors).
I got it used, fixed the door spring and had it for about 10 years.
When it stopped working I called Amana and asked, figuring she might
know which part failed most frequently. She suspected the
magnetron. The next time I called, someone suspected the diode. I
opened the high voltage cage**** and saw that there were cracks on the
wires to the diode (one 20 or 30 times bigger than yours, counting
heat radiation fins). I used silicione sealant by GE (available in
black at auto parts stores, if color matters to the repairer) and put
on large blobs of it, thicker than the thick wires. And it worked for
another 10 years.
****The woman at Amana was very much afraid I wouldn't put the woven
metal gasket back the way it had been and that it would leak. She
also wouldn't send me a schematic. I had to promise her up and down
that I had 20 years experience with electronics, and I would put the
gasket just where it was, and she finally sent me a schematic, for
free. I had to take apart another one^^ and I think they are
designed differently now, but I would be very careful reassembling so
as to not leak microwaves.
The next time it failed it did nothing, so it was the transformer. I
think Amana wanted 380 dollars I said, "That's the price from 1970.
They are worth less now (since you can buy a whole microwave for under
100.) After writing a letter -- I said, Save a few for your museum
and the inventor's grandchildren and sell the rest at a price at which
you will actually sell them -- and being referred to a place near
Harrisburg, they lowered the price to the wholesale price, 250 or so.
Much as I hated to part with model 2, I scrapped it.
^^This latest one has a bad relay, and I'll probably never get around
to fixining it.
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