Microwave dead - what to do??

markwilliams · 5094

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Offline markwilliams

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on: October 02, 2011, 05:18:27 AM
What, if anything, audio related can be done with that BIG transformer in my dead microwave?

I think it would be a shame to put it in a landfill!

Mark
« Last Edit: October 02, 2011, 05:24:07 AM by markwilliams »


Offline Jim R.

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Reply #1 on: October 02, 2011, 10:25:06 AM
First things first -- be ultra careful in there!  There's most likely enough residual charge in ther to transport you to the next world very quickly.

As for that much voltage, well, maybe a baby on-gaku?

Without voltage and current ratings, it's difficult to say if an audio project is suitable.  Maybe a giant, wall-size bug zappe?

Don't laugh, some friends of mine once lived in the deep woods and we built an 8 foot tall, 16 foot wide bug zapper that seemed to do the trick, but how much ozone we inhaled while watching it do its thing is not something I want to think about :-).

-- Jim

Jim Rebman -- recovering audiophile

Equitech balanced power; uRendu, USB processor -> Musette DAC -> 5670 tube buffer -> Finale Audio F138 FFX -> Cain and Cain Abbys near-field).

s.e.x. 2.1 under construction.  Want list: Stereomour II

All ICs homemade (speaker and power next)

Offline markwilliams

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Reply #2 on: October 02, 2011, 10:34:38 AM
He, he Jim!

We could use a giant bug zapper here in NE Pennsylvania.  Recent floods have recent increased the mosquito population!

I have no idea about the secondary voltage, etc. on this rather large transformer!    Actually, I'm not really certain how to measure it.   Do I simply wire it up to 110vac then carefully take a reading on the secondary wires with my V.O.M. set to A/C?

I intend to pull it from the unit nonetheless.    Somewhere, someone will find it useful.

Mark


Offline JC

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Reply #3 on: October 02, 2011, 12:08:41 PM
As a rule, not much.  The filament winding for the cavity magnetron is usually about 3 Volts; lots of current, though.  The HV winding is maybe a couple of thousand Volts.

I have one of these sitting around and have thought that it might make the basis of a supply for a Jacob's Ladder, or maybe a plasma tweeter.

Jim C.

Offline Grainger49

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Reply #4 on: October 02, 2011, 02:07:15 PM
A way to safely determine the output voltage of the transformer is to feed it low voltage 60Hz sine waves.  Say feed with a 6.3V AC heater transformer or bring it up to 4 or 5V on a variac.

Measure the incoming voltage to the Microwave transformer and the output voltage from it.  Then a tiny bit of math will tell you what it would put out with 120V coming in.  
« Last Edit: October 03, 2011, 12:23:58 AM by Grainger49 »


Offline rif

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Reply #5 on: October 02, 2011, 02:08:48 PM
I saw on the web someone turn one into a diy welder.

-david

Offline JC

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Reply #6 on: October 02, 2011, 02:40:39 PM
Another thing to be aware of: many of these transformers have one side of their HV secondary attached internally to the frame of the transformer; no separate lead, they just use the sheet metal of the case on which the transformer is mounted as a circuit path.

Jim C.

Offline Jim R.

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Reply #7 on: October 02, 2011, 03:06:50 PM
Mark,
Ditto what Granger said.  With a couple Kv likely on the HV secondary, if you feed the primary the full 120 volts, you're likely to fry a meter.  In either case, just be careful with this stuff.  I have a lot of experience working with high voltages and once you're above 1k, things can start to get a little weird, and downright freaky when you get into the 100 kv + range -- lots of special equipment needed for that stuff though.

Alsom, if you have a variac, that could be a good place to start exploring the secondaries.

HTH,

Jim

Jim Rebman -- recovering audiophile

Equitech balanced power; uRendu, USB processor -> Musette DAC -> 5670 tube buffer -> Finale Audio F138 FFX -> Cain and Cain Abbys near-field).

s.e.x. 2.1 under construction.  Want list: Stereomour II

All ICs homemade (speaker and power next)

Offline markwilliams

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Reply #8 on: October 03, 2011, 01:50:13 AM
Thanks all you guys!

I'm out of my league here so I think I will back off on trying to salvage the transformer, or thinking it might be useful for audio.    Seems like special equipment is needed, etc.   

On the up side though -- I looked around on YouTube about possible repairs.    If I am checking it correctly, I think there's a diode that hangs off the large capacitor that may have gone bad.   

So I guess my teachings from Grainger and this forum have paid off somewhat because when it went down initially I said to my wife "It's probably a fuse or diode."   Knowing that fuses usually don't blow for no reason I secured a fuse anyway -- and it of course blew.   (But NOT from just plugging it in.  The display was fine.   The fuse blew only when I actually tried to microwave something.)   So, that told me something.   

It's not that the thing is worth so much.  For me, it seems dumb to throw something repairable in a landfill.   And it's the fun of getting it working again!   If I do get this fixed with a diode I'll give it away.   Lots of folks got flooded here in NE Pennsylvania recently so someone will need it.   

Point is.....this basic interest in electronics and this forum and the guys on it have indeed taught me at least a few basic things over the years.   

Thanks to Doc, Grainger, the rednecks on YouTube (a constant source of amazement!), and everyone else!

Mark Williams
 


Offline Wanderer

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Reply #9 on: October 03, 2011, 07:01:53 AM
Quote from: markwilliams on October 02, 2011, 05:18:27 AM
What, if anything, audio related can be done with that BIG transformer in my dead microwave?

I think it would be a shame to put it in a landfill!

Mark

Me, I am thinking "Death Ray".

http://www.engadget.com/2006/10/23/inventors-claim-to-turn-300-microwaves-into-megawatt-energy-weap/

Once you conquer the universe, or at least the world, seems you can get any audio system you want.

   

Kevin R-M

Offline markwilliams

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Reply #10 on: October 03, 2011, 07:24:06 AM
Ha!   

Death Ray!
Love it!   But shouldn't we at least try diplomacy first?

Mark


Offline Laudanum

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Reply #11 on: October 03, 2011, 09:31:53 AM
From reading the abstract, it sounds like they're crossing the streams.  Never cross the streams !!!

Desmond G.

Offline JC

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Reply #12 on: October 03, 2011, 09:36:14 AM
About that diode: My meter apparently won't check one properly.  It shows a microwave diode as "open" in both directions, even though it is a good part.  I don't know how it would do with a shorted one, since the only such microwave diode I have encountered blew itself to smithereens and required no testing!

If you spend some time looking on the web, you should be able to find some pointers on how to check the magnetron for shorts.  If that seems to be OK, it may be worth the effort to get a replacement diode.  Naturally, it will need to be one specifically for microwave use because of the high Voltage.  If you have an appliance parts distributor in town, that may be a good place to inquire. 

BTW, you should also run across some instructions about draining that capacitor before you do anything else!  That sucker may not have enough storage to kill you outright, but it can sure knock you back into something hard that hurts!

Really, the microwave part of the circuit usually consists of the transformer, the diode, the capacitor, and the magnetron.  If you can rule out the magnetron...

Jim C.

Offline Wanderer

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Reply #13 on: October 03, 2011, 09:43:10 AM
Quote from: markwilliams on October 03, 2011, 07:24:06 AM
Ha!   

Death Ray!
Love it!   But shouldn't we at least try diplomacy first?

Mark

I don't know fer sure but I'd bet diplomacy would work tons better if you already had a Death Ray.

....assuming Flash Gordon or James Bond didn't show up and screw the whole thing up.   

Kevin R-M

Offline bobster

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Reply #14 on: October 03, 2011, 02:05:05 PM
I am laughing out loud and my family is looking at me strangely.

The image that came to mind was Stewie on Family Guy building these electronic contraptions that an adult couldn't build.  I believe that one of them was a DEATHRAY,

Bob Musson
Seduction (extended), Foreplay, Paramours, Klipsch Heresys, Orcas, Crack plus HD 600s
Lovin the Bottlehead sound in Maryland

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