Sharp microwave arcs *through* front door

[Ron(UK)]

Mains wont jump 2 inches !!!!!!

It`s not mains voltage and it`s not mains frequency, is it?

Ron(UK)

 

[Chris]

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

 

[Gordon Bennett]

I've got a ~2 year old microwave that has shown no previous signs of
trouble and is to all appearances in good working order. During
normal operation (melting butter on low power) this morning we heard
a
familiar 60Hz buzz, and then sure enough it shot an arc out through
the door to metal rack across a gap of some two inches. Following
the
burn marks back, the arc seems to have originated (or at least
exited)
beneath the chamber, where the inside of the door meets the body of
the oven and roughly halfway across from the hinges. First the big
question: whatever the failure was, shouldn't there have been a
better path to ground available? Do I have some kind of grounding
issue that I need to fix in before I repair this thing and start
using
it again? >
-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.

 

[Ron(UK)]

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.

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


Ron(UK)

 

[Sam Goldwasser]

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?

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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[jakdedert]

Chris wrote:

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.

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

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

 

[TMI]

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.

 

[TMI]

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.

 

[[email protected]]

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

 

[William Sommerwerck]

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.

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.

 

[[email protected]]

http://www.southgatearc.org/news/february2007/history_of_the_magnetron.htm

If you are ever in London, say Hello to ''Maggie'' Magnetron for me.
cuhulin
www.incallander.co.uk/music/maggiemp3.wav

 

[Michael A. Terrell]

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.

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

 

[William Sommerwerck]

William Sommerwerck wrote:

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

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

 

[[email protected]]

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
www.cattledog.com www.acdca.org 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?
...................

 

[[email protected]]

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

 

[Michael A. Terrell]

cuhulin

--
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

 

[Michael A. Terrell]

cuhulin

--
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

 

[bz]

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.
....

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

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.

[email protected] remove ch100-5 to avoid spam trap