Sharp microwave arcs *through* front door

Thanks for all the replies. Its beginning to sound like I was right to feel baffled. Its certainly not mains voltage, but before the arc there was a buzz that sounded like mains frequency. Since you cant see a flicker even at 60Hz (I'm in the US), I don't know the frequency of the arc itself.

Ron: I had wondered if it was possible that the door had lost contact (grease in the hinges?) with the chassis and was therefore able to charge up. It still seems like it would have been easier to jump back to the chassis than across the gap, but then I have two burn marks, so maybe it went out into the door and then back to the chassis a ways down for a while before hand?

Sam: I completely agree with both you and Ron that this seems far- fetched. It seemed so unlikely that I started think I'd just made up having seen the arc, and I wouldn't believe it if I didn't have the burn marks staring me in the face. I also completely agree with your reasoning for ruling out the HV as the explanation. Even so, I still have some problems with the load explanation that I need to answer before I trust my kitchen again. First, and most important, by the same argument you made ruling out HV problems as the source, shouldn't any spark created inside the oven by whatever mechanism be contained by the chassis unless something has gone horribly wrong? On the other hand, proceeding from the assumption that its impossible for the entire chassis from floating up high enough to do this, is it even possible for a load problem to cause a really large arc? In ballpark figures, the oven is rated at ~1000 watts, the magnetron is some ~50% efficient, say, so there can't be more than a than a few hundred watts of microwaves bouncing around, right? Even if you made a tuned resonator (one of these graphite and aluminum foil gizmos, for example), and had no other load, is it possible to recover that energy efficiently enough to something like this? At any rate, to be clear, nobody thinks that in the absence of other problems I have reason to doubt my house ground?

Thanks again. I'll keep cooking with one hand in my pocket for now.

Chris

The only grounding isuue that I can think of that would cause this type of fault is that your house is built on the site of an old indian burial ground. You need an exorcist immediately.

If I were you, I`d replace the oven!

Ron(UK)

Did the fireworks happen *instantly* when you pushed START? Instantly means in a fraction of a second.

Any effect would have 60 Hz in it since the microwaves are generated in pulses that have 100 percent ripple at 60 Hz.

Could there be a 2 inch arc from 1000 W of microwaves? Sure.

And a half stick of butter or whatever is probably not a very good absorber so some sort of peculiar resonant cavity effect is quite possible. And, if there was dirt, grime, and goop :) in the area of the door where the arcing took place, even more possible.

Beyond that, I'd say you have to try some more experiments. :-)

To be sure, check your outlet ground with a multimeter or outlet tester. But plenty of microwave ovens are used without proper grounds despite the warnings.

I can't imagine any problem with the house ground that wouldn't result in other issues.

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I can understand a purely academic curiosity as to the cause of this--and I sympathize with the economics involved--but I think (actually, I'm sure) if it were me, I'd follow the advice below.

Failing that, I'd get professional--and by professional, I mean engineering--help. Either involve the manufacturer, and/or a consumer products testing agency. This just ain't s'posed to happen, doesn't often--if ever before--happen; and most importantly, involves serious safety issues.

You may trigger a product recall, save some lives or prevent some injuries...and maybe even get a new oven in the process.

Failing all that, toss it and pick up one for $15-25 at a thrift store. I've done that many times....

jak

This unit is defective. The manufacturer should be contacted for a replacement. Discontinue use at once. Fireworks inside are one thing. The moment they reach outside, it is something entirely different! Large amounts of microwave energy are leaking and could seriously burn your eyes, nasal passages, lungs and internal organs before your skin.

Stop screwing around with this one.

The manufacturer SHOULD be willing to replace it for the sake of liability alone.

This unit is defective. The manufacturer should be contacted for a replacement. Discontinue use at once. Fireworks inside are one thing. The moment they reach outside, it is something entirely different! Large amounts of microwave energy are leaking and could seriously burn your eyes, nasal passages, lungs and internal organs before your skin.

Stop screwing around with this one.

The manufacturer SHOULD be willing to replace it for the sake of liability alone.

About twenty five something years ago, I read a book about the magnetron.A guy in England had the secret of the magnetron and he was going from somewhere to somewhere else and he had an armed guard guy traveling with him.The armed guard guy had orders to shoot and kill the magnetron guy if he was about to be captured by the enemy.

Another article in that book was something about a Military Aircraft hanger that was made of wood.(in Germany, I think it was) The Radar system at that Base in Gemany was making the nails in that hanger glow red hot and with popping noises too, they wound up having to do some readjustments with that Radar system.Do you remember the Radar Ranges, Microwave ovens? cuhulin

This is an absurd urban legend.

Microwaves have to be absorbed to heat something. Metallic objects reflect microwaves and are therefore not heated.

A microwave field with sufficient power to heat nails red-hot (assuming the nails absorbed the energy, which they don't) would quickly kill any living thing in that field.

If you are ever in London, say Hello to ''Maggie'' Magnetron for me. cuhulin

WIlliam, you need to update your 'Skippy" list.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

Perhaps, but that sort of wildly incorrect statement needed explicit refutation. Someone in this group might have believed it.

Skippity Doo Da, that old song by what's her name, Skippity Do Da Day. It's pouring down raining cats and dogs and tree frogs outside now.Doggy, just now kissed my right ear.(that means she

has to put my dog leash on me and take me out in the front yard) Let me get my mini brella, old worn out pith cat hat on. cuhulin ................... Donna Fargo? ..................

incallander.co.uk About six/seven years ago, Barbara Lynch, from Limerick,Ireland (she lives in the Hotlanta area) [[forced me]] to dig up the Raglan Road song for her.Only took me about ten minutes.Barb, you know I am your number one fan club. cuhulin

Chris wrote in news:5a8793cc-df83-4935-b543- snipped-for-privacy@b1g2000pra.googlegroups.com:

I would follow the advice of the others and contact the manufacturer immediately, discontinue use!

Treat the oven like you would a live bomb!!! [Cut the circuit breaker, unplug the oven, turn the circuit breaker back on]

Supply them with pictures [as best you can reconstruct] the exact configuration of the oven, its contents, and the rack. Along with diagrams and pictures of the burn marks.

My best guess as to something that might cause the arcing you observed is highly unlikely:

1) the vapors from the heated butter [moist air and fat] producing a conductive path inside the oven that happened to resonant at the magnetron frequency. 2) The door and the metal rack also forming a resonant circuit. 3) capacitive coupling THROUGH the metal screen built into the door. 4) ionization of the air between the door and the rack, perhaps by a stray cosmic ray that 'kicked off' the arc. 5) Your house just happened [for a few moments] to be at a point of resonance in the 60 Hz power grid that covers the country. Or a resonant, ionized path, within the area around the power transformer that allowed a similar arc that allowed [intermittently] the 60 Hz HV AC to jump from transformer to case to rack[there should be burn marks near the transformer, also.

Question: where did the 'power' go after jumping to the metal rack? Any 'exit wounds'

None of the points seem probable but all seem barely possible. Comment: YOU are lucky to be alive. Think about that arc jumping to YOU.

I used to fix radars for a living and I have seen some 'odd' things happen, but nothing as odd as what you described.

--
bz

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an 
infinite set.

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