On Mon, 26 Aug 2013 04:18:18 +0000 (UTC), "Danny D."
wrote:

I just tested my microwave diode where, unfortunately, it seems to be good:
see other post for picture.

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).

Since apparently there is no current in that direction, how about
taking out the resistor and seeing what it says then?

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.

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
anyhow.
http://www.ebay.com/itm/Micronta-Mic...-/290963447557

and a new one for only 15 including shipping
http://www.ebay.com/itm/General-MLD1...-/200952444879

Here's one for more, $35 http://www.lessemf.com/mw-oven.html

And http://www.ebay.com/bhp/microwave-leak-detector

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'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.