Does my microwave diode look good to you?

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I just tested my microwave diode where, unfortunately, it seems to be good: http://farm8.staticflickr.com/7358/9594179589_09dac4708b_o.fig
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?
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On Mon, 26 Aug 2013 04:18:18 +0000, Danny D. wrote:

Ooops.
http://farm8.staticflickr.com/7358/9594179589_09dac4708b_o.gif
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On Mon, 26 Aug 2013 04:18:18 +0000 (UTC), "Danny D."

7 volts or 0.7 volts. It should 0.7
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On 08/25/2013 09:39 PM, snipped-for-privacy@aol.com wrote:

It's a microwave diode, which can be thought of as several Si diodes in series, so you would expect a higher forward drop than a single junction.
Jon
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On 8/26/2013 2:16 AM, Jon Danniken wrote:

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. ^_^
http://www.repairfaq.org/REPAIR/F_micfaq5.html
TDD
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The Daring Dufas wrote:

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:
http://www.youtube.com/watch?v=tTPO2eGz71s

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).
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On 8/26/2013 6:51 AM, Danny D. wrote:

One YouTube video shows a fellow using 120VAC from a wall outlet along with a resistor and DMM to check one of the diodes. ^_^
TDD
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if it does everything but heat it might be the magnatron http://www.ehow.com/info_8231169_can-magnetrons-replaced-microwaves.html
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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 anyhow. http://www.ebay.com/itm/Micronta-Microwave-Leakage-Detector-/290963447557
and a new one for only 15 including shipping http://www.ebay.com/itm/General-MLD100-Microwave-Leak-Detectors-/200952444879
Here's one for more, $35 http://www.lessemf.com/mw-oven.html
And http://www.ebay.com/bhp/microwave-leak-detector

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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On Mon, 26 Aug 2013 02:19:29 -0400, micky wrote:

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.
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"Arfa Daily"

** The OP is just begging for a Darwin Award.
So who are you to spoil his one moment of fame ??
http://en.wikipedia.org/wiki/Darwin_Awards
How amazing to find that the famous Award originates with USENET !!!!!!!
.... Phil
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That's true of most DMMs, but there are exceptions. My Keithley 2000 will bias a diode up to 10VDC. Useful for checking smaller zeners as well.
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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. .
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On Mon, 26 Aug 2013 15:28:18 -0400, micky wrote:

Except there isn't 9 volts across the diode. There was 7 volts across the diode.
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On Tue, 27 Aug 2013 00:46:55 +0000 (UTC), "Danny D."

That was forward biased. My reply was clearly about reverse biased. If you hadn't snipped so much and didn't want so much for me to be wrong, you'd have noticed.
Quote

End Quote.
I added the blank line between your first and second line so there'd be no doubt which direction I was talking about.
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Would it make sense to hook the diode to a 9 v transistor battery in each polarity, and measure the milliamps current in each direction?
. Christopher A. Young Learn about Jesus www.lds.org .
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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 k.
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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.
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On Tue, 27 Aug 2013 07:28:09 -0400, Stormin Mormon wrote:

"Normal" diodes would fry under those circumstances; but I don't know what would happen with high-voltage diodes. That's why I have the resistor there.
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On Mon, 26 Aug 2013 15:17:35 +0100, Arfa Daily wrote:

Thanks for that confirmation. Bummer. But now at least I know it's most likely the magnetron.
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