I just tested my microwave diode where, unfortunately, it seems to be good:
Forward biased with a 9 VDC battery, I measure 7 VDC across the diode;
reverse biased, I read 9 VDC across the diode (given a 200 ohm
current-limiting resistance in series with the battery).
I was hoping the diode was bad, because otherwise, I don't know what's
wrong with the microwave. It does everything but heat up the food.
It makes noise, the lights light up fine, the controls all work,
and it beeps when done, etc. - but it just won't heat up anything.
Did I test the diode properly?
I thought I remembered seeing a diagram of the makeup of the internal
construction of a high voltage diode for a microwave oven and it had
several diodes in series inside the molded package. I tried to find an
example on The Web but couldn't find it in a short time but here's a
link to good information on testing the components in a microwave oven. ^_^
That's a nice reference.
It looks like my test of the high-voltage diode is
similar in that they suggest 15 volts and 240 ohms,
whereas I used 9 volts and 200 ohms.
Here's a Youtube:
They all seem to use 15 volts or so, whereas I used
9 volts - so I'll try again with a higher voltage
(but I doubt it makes much of a difference).
On Mon, 26 Aug 2013 04:18:18 +0000 (UTC), "Danny D."
see other post for picture.
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.
The resistor is to prevent the diode from burning
up with too much current, I believe.
If I take out the resistor, I probably blow up the diode.
That does not sound like good advice, so I didn't read the
rest of the suggestions for fear of being led astray.
** The OP is just begging for a Darwin Award.
So who are you to spoil his one moment of fame ??
How amazing to find that the famous Award originates with USENET !!!!!!!
On Mon, 26 Aug 2013 11:58:37 +0000 (UTC), "Danny D."
I think so too.
Now why would you think that? Did you fail to notice that if there
is 9 volts across the diode, there is no current running through the
diode. How can you imagine that removing a 200 ohm resistorr will
increase the current much? And with a 9-volt battery no less.
Since ;your answer does not sound like you think well, I won't read
the rest of your posts, for fear I'll read foolishness but be too weak
to avoid believing it. .
On Tuesday, August 27, 2013 7:28:09 AM UTC-4, Stormin Mormon wrote:
I've tested microwave high voltage with a regular meter. Carefully arrange
a few high ohm resistors in series across the high voltage supply. So the
total is 20 or more meg ohms. Like three 9.1m and one 1m. Use 1/2 watter
s as there will still be some current involved. Put the small one on the g
round side. Measure the voltage across the small resistor. Get it all set
up so you're not touching anything at all before you power it own. Make su
re none of your wires are close to anything else or a ground. Based on you
r meter reading and the resistors you used you can calculate the total volt
age. Keep in mind you are still fooling around with deadly voltages with e
nough current available to kill you in an instant. Proceed at your own ris
While you might get away doing it this way, look at the voltage ratings of
the 1/2 watt resistors. Most are rated for less than 500 volts , so you are
getting close or over the voltage ratings for many when they are in series.
There are some resistors rated for more voltage.
The meter leads probalby are not rated for over 1000 volts either, so make
sure you are not holding them incase the one on the ground side opens up.
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.