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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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Sharp microwave arcs *through* front door
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? As for the cause of the arc, since it was able to arc across such a large gap I assume the failure involves the high voltage components, not the transformer or anything else seeing AC line power, so maybe the diode? The capacitor would fail short, so that can't be it, right? The local repair shop swore this was impossible, and I haven't been able to turn up any previous posts covering external arcs, except one from back in 2000 out the top of the oven, so hopefully this isn't redundant. Has anyone else encountered something like this or have an idea as to what might be going on? Thanks. -Chris |
#2
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Sharp microwave arcs *through* front door
Are the door seals clean? Does the door close firmly and evenly?
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#3
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Sharp microwave arcs *through* front door
On Dec 15, 6:09 pm, "William Sommerwerck"
wrote: Are the door seals clean? Does the door close firmly and evenly? The door seals were passable, but not immaculate. The door itself seems to close perfectly normally. It is relatively new and lightly used, and there aren't any glaring issues like that. We did do some work on our house a while back and stirred up a lot of dust in the process, so contamination is a possibility. Supposing something like that was the cause of the arc, shouldn't it have still have followed some other path? |
#4
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Sharp microwave arcs *through* front door
Chris wrote: 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) That isn't a suitable load for a microwave is it ? You need some water in there. No surprise it arced. Graham |
#5
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Sharp microwave arcs *through* front door
Chris wrote: "William Sommerwerck" wrote: Are the door seals clean? Does the door close firmly and evenly? The door seals were passable, but not immaculate. The door itself seems to close perfectly normally. It is relatively new and lightly used, and there aren't any glaring issues like that. We did do some work on our house a while back and stirred up a lot of dust in the process, so contamination is a possibility. Supposing something like that was the cause of the arc, shouldn't it have still have followed some other path? The cause of the arc was the absense of anything in the oven that could absorb the microwave energy effectively. Graham |
#6
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Sharp microwave arcs *through* front door
That isn't a suitable load for a microwave is it ? You need some water in
there. No surprise it arced. Graham I thought about that, but then I've done it a hundred times with no problem, and the micro wave has a build in 'melt butter' function, which seems to run it on low power for short bursts. That's what we were using at the time, so I dont think the load was the issue. Again though, even if that were the problem, shouldn't the arc have been contained? -Chris |
#7
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Sharp microwave arcs *through* front door
On Sat, 15 Dec 2007 14:53:45 -0800 (PST), Chris
wrote: 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? Yes, and you may want to check the outlet's ground wire just in case. But the sink may have been a lower impedance ground? Do I have some kind of grounding issue that I need to fix in before I repair this thing and start using it again? Myself, I'm not sure I'd *want* to try to fix it! As for the cause of the arc, since it was able to arc across such a large gap I assume the failure involves the high voltage components, not the transformer or anything else seeing AC line power, so maybe the diode? The capacitor would fail short, so that can't be it, right? The local repair shop swore this was impossible, and I haven't been able to turn up any previous posts covering external arcs, except one from back in 2000 out the top of the oven, so hopefully this isn't redundant. Has anyone else encountered something like this or have an idea as to what might be going on? Thanks. Yes, check the door gasket? -Chris |
#8
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Sharp microwave arcs *through* front door
"Eeyore" wrote in message ... Chris wrote: 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) That isn't a suitable load for a microwave is it ? You need some water in there. No surprise it arced. Even an empty microwave should never arc to the outside, I've never, ever seen that before, and I too have used microwaves to melt butter hundreds of times over the decades. |
#9
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Sharp microwave arcs *through* front door
"Eeyore" wrote in message
... Chris wrote: 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)... That isn't a suitable load for a microwave, is it? You need some water in there. No surprise it arced. I don't think that's correct. Butter contains water and fat, both of which absorb microwaves. I've melted butter without problems. Arcing usually occurs at a sharp metal edge. I once put a plastic jar of Adams peanut butter in my microwave to soften it up, and got serious arcing on the teensy bits of aluminum foil that had been left behind when I peeled off the inner seal. |
#10
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Sharp microwave arcs *through* front door
"Chris" wrote in message
... On Dec 15, 6:09 pm, "William Sommerwerck" wrote: Are the door seals clean? Does the door close firmly and evenly? The door seals were passable, but not immaculate. The door itself seems to close perfectly normally. It is relatively new and lightly used, and there aren't any glaring issues like that. We did do some work on our house a while back and stirred up a lot of dust in the process, so contamination is a possibility. Supposing something like that was the cause of the arc, shouldn't it have still have followed some other path? ¿Quien sabe? I would thoroughly clean everything, inside and out. Also check to see that there are no bits of foil, or anything metallic, in the oven, on or around the seals, etc. |
#11
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Sharp microwave arcs *through* front door
William Sommerwerck wrote:
"Eeyore" wrote in message ... Chris wrote: 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)... That isn't a suitable load for a microwave, is it? You need some water in there. No surprise it arced. I don't think that's correct. Butter contains water and fat, both of which absorb microwaves. I've melted butter without problems. Arcing usually occurs at a sharp metal edge. I once put a plastic jar of Adams peanut butter in my microwave to soften it up, and got serious arcing on the teensy bits of aluminum foil that had been left behind when I peeled off the inner seal. I've had that happen recently. Same product (different brand)--some surprisingly SERIOUS fireworks immediately as I hit the button. If the lights had been off, it would have lit the entire kitchen from really minuscule bits of foil. I'm with the other poster, in that I'm not sure I'd ever trust that unit again. jak |
#12
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Sharp microwave arcs *through* front door
I would thoroughly clean everything, inside and out. Also check to see that there are no bits of foil, or anything metallic, in the oven, on or around the seals, etc. Yeah, I'll double check. Also noticed a second burn mark closer to the hinges, but same vertical position. Just to clarify my description of the problem, I'm not talking about an arc like you'd see from a little metal in the microwave. I'm talking about a beefy pink arc about the diameter of a pencil. |
#13
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Sharp microwave arcs *through* front door
James Sweet wrote: "Eeyore" wrote Chris wrote: 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) That isn't a suitable load for a microwave is it ? You need some water in there. No surprise it arced. Even an empty microwave should never arc to the outside, I agree it shouldn't have arced to the *outside*. I've never, ever seen that before, and I too have used microwaves to melt butter hundreds of times over the decades. Ok. I have heard of other stories where people have done things with their microwave ovens the makers don't recommend and been puzzled why it broke after say the hundredth time though. Graham |
#14
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Sharp microwave arcs *through* front door
William Sommerwerck wrote: "Eeyore" wrote Chris wrote: 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)... That isn't a suitable load for a microwave, is it? You need some water in there. No surprise it arced. I don't think that's correct. Butter contains water and fat, both of which absorb microwaves. I've melted butter without problems. Maybe the quantity wasn't enough ? Graham |
#15
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Sharp microwave arcs *through* front door
Nah, it was a half a stick, well within the pre-programmed range, so
that's not it. In any case, some bit of foil of just the right size or shape can lead to gradients high enough to get sparks, but this was not like this. This was some large fraction of the entire current output of the transformer, like the fireworks you see on youtube when people have pulled the guts out of the microwave and using it just to make an arc. |
#16
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Sharp microwave arcs *through* front door
"Eeyore" wrote in message
... William Sommerwerck wrote: "Eeyore" wrote Chris wrote: 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)... That isn't a suitable load for a microwave, is it? You need some water in there. No surprise it arced. I don't think that's correct. Butter contains water and fat, both of which absorb microwaves. I've melted butter without problems. Maybe the quantity wasn't enough? I'm not sure. The "received knowledge" on such things is that if there's nothing in the oven to absorb the microwaves, the magnetron will eventually overheat (from the reflected unabsorbed energy). The lower the power setting, the less likely this is to happen. But overheating isn't arcing. Arcing requires a sharp metallic edge for the electric field to build to a point where the air breaks down. |
#17
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Sharp microwave arcs *through* front door
"Chris" wrote in message
... Nah, it was half a stick, well within the pre-programmed range, so that's not it. In any case, some bit of foil of just the right size or shape can lead to gradients high enough to get sparks, but this was not like this. This was some large fraction of the entire current output of the transformer, like the fireworks you see on youtube when people have pulled the guts out of the microwave and using it just to make an arc. If a thorough cleaning and inspection doesn't resolve the issue, I'd get a new unit. The potential for damage or injury seems too great. |
#18
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Sharp microwave arcs *through* front door
Chris writes:
Nah, it was a half a stick, well within the pre-programmed range, so that's not it. In any case, some bit of foil of just the right size or shape can lead to gradients high enough to get sparks, but this was not like this. This was some large fraction of the entire current output of the transformer, like the fireworks you see on youtube when people have pulled the guts out of the microwave and using it just to make an arc. This whole thing doesn't sound right. Regardless of whether the microwave oven is attached to Earth ground, the return path for the high voltage IS the chassis of the microwave oven. It would be almost impossible for that to be disrupted as the magnetron and HV transformer are bonded to the chassis. So, it's highly unlikely that the HV current (not the microwave energy) would want to jump from the oven to an external ground. Looking at the typical schematic, it's hard to come up with any sort of failure mode where such a potential difference would appear between the chassis and ground. I'm not saying something very peculiar didn't happen. Just that an explanation relating to the HV power doesn't make sense. I'd quicker go with some combination of load (butter), dirt, and other factors affecting the microwave distribution. --- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/ Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/ +Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm | Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html Important: Anything sent to the email address in the message header above is ignored unless my full name AND either lasers or electronics is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs. |
#19
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Sharp microwave arcs *through* front door
Sam Goldwasser wrote:
Chris writes: Nah, it was a half a stick, well within the pre-programmed range, so that's not it. In any case, some bit of foil of just the right size or shape can lead to gradients high enough to get sparks, but this was not like this. This was some large fraction of the entire current output of the transformer, like the fireworks you see on youtube when people have pulled the guts out of the microwave and using it just to make an arc. This whole thing doesn't sound right. Regardless of whether the microwave oven is attached to Earth ground, the return path for the high voltage IS the chassis of the microwave oven. It would be almost impossible for that to be disrupted as the magnetron and HV transformer are bonded to the chassis. So, it's highly unlikely that the HV current (not the microwave energy) would want to jump from the oven to an external ground. Looking at the typical schematic, it's hard to come up with any sort of failure mode where such a potential difference would appear between the chassis and ground. I'm not saying something very peculiar didn't happen. Just that an explanation relating to the HV power doesn't make sense. I'd quicker go with some combination of load (butter), dirt, and other factors affecting the microwave distribution. It could be possible that some part of the door, possibly one of the hinges has lost it`s bonding to chassis earth and a potential is building up there then striking to the nearest earthed metal. it`s unlikely tho in my experience. There was a model of Phillips oven that could build up a charge on the thin aluminium cover over the lamp leading to quite spectacular arcing around the rivet which held it in place and acted as a swivel. A poor connection there was indicated by quite strong leakage of microwave radiation through the plastic menu strip on top of the oven. Ron(UK) |
#20
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Sharp microwave arcs *through* front door
On 15 Dec, 23:09, "William Sommerwerck"
wrote: Are the door seals clean? Does the door close firmly and evenly? Mains wont jump 2 inches !!!!!! |
#21
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Sharp microwave arcs *through* front door
Marra wrote:
On 15 Dec, 23:09, "William Sommerwerck" wrote: Are the door seals clean? Does the door close firmly and evenly? Mains wont jump 2 inches !!!!!! It`s not mains voltage and it`s not mains frequency, is it? Ron(UK) |
#22
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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 |
#23
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Sharp microwave arcs *through* front door
"Chris" wrote in message ... 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. |
#24
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Sharp microwave arcs *through* front door
Chris wrote:
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) |
#25
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Sharp microwave arcs *through* front door
Chris writes:
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. --- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/ Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/ +Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm | Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html Important: Anything sent to the email address in the message header above is ignored unless my full name AND either lasers or electronics is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs. |
#26
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Sharp microwave arcs *through* front door
Ron(UK) wrote:
Chris wrote: snip Thanks again. I'll keep cooking with one hand in my pocket for now. 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 Ron(UK) |
#27
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Sharp microwave arcs *through* front door
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. On Dec 17, 8:32 am, Sam Goldwasser wrote: Chris writes: 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. --- sam | Sci.Electronics.Repair FAQ:http://www.repairfaq.org/ Repair | Main Table of Contents:http://www.repairfaq.org/REPAIR/ +Lasers | Sam's Laser FAQ:http://www.repairfaq.org/sam/lasersam.htm | Mirror Sites:http://www.repairfaq.org/REPAIR/F_mirror.html Important: Anything sent to the email address in the message header above is ignored unless my full name AND either lasers or electronics is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs. |
#28
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Sharp microwave arcs *through* front door
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. On Dec 17, 8:32 am, Sam Goldwasser wrote: Chris writes: 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. --- sam | Sci.Electronics.Repair FAQ:http://www.repairfaq.org/ Repair | Main Table of Contents:http://www.repairfaq.org/REPAIR/ +Lasers | Sam's Laser FAQ:http://www.repairfaq.org/sam/lasersam.htm | Mirror Sites:http://www.repairfaq.org/REPAIR/F_mirror.html Important: Anything sent to the email address in the message header above is ignored unless my full name AND either lasers or electronics is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs. |
#29
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Sharp microwave arcs *through* front door
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 |
#30
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Sharp microwave arcs *through* front door
wrote in message
... 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. |
#31
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Sharp microwave arcs *through* front door
http://www.southgatearc.org/news/feb..._magnetron.htm
If you are ever in London, say Hello to ''Maggie'' Magnetron for me. cuhulin www.incallander.co.uk/music/maggiemp3.wav |
#32
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Sharp microwave arcs *through* front door
William Sommerwerck wrote:
wrote in message ... 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. 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 |
#33
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Sharp microwave arcs *through* front door
"Michael A. Terrell" wrote in message
... William Sommerwerck wrote: wrote in message ... 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. 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. |
#34
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Sharp microwave arcs *through* front door
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? ................... |
#35
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Sharp microwave arcs *through* front door
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 |
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Troll
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Troll
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Sharp microwave arcs *through* front door
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