Another Microwave question

Discussion in 'General Electronics Chat' started by Gdrumm, May 29, 2015.

  1. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
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    Does the magnatron want to emit the radio waves horizontally rather than vertically?

    All of the microwaves I've seen have a magnatron mouted so as to emit the radio waves horizontally.

    While trying to fix a new type Microwave / Grill (combination conventional grilling mechanism attached to the back of the MWO), I found that the magnatron was turned in such a way as to fire the rays up, then a metal cover took that, and bent it 90 degrees, so that the waves would then go in through the side of the cabinet (like a normal MWO does.

    Long story short, the magnatron is shorted out, and I don't have a duplicate. They cost between $45.00 to $100.00, so my friend told me to just keep the thing for parts.

    I read on the internet that microwaves can be effected by gravity, so I'm just wondering if this is a poor design, and that's why the magantron got shorted out.

    Does anyone have any insights on this?
    Please see crude drawing showing what I mean.
    Thanks
     
  2. nsaspook

    AAC Fanatic!

    Aug 27, 2009
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    Don't believe what you read on the Internet.;) The metal cover is just a simple waveguide or reflector into the cooking cavity. Very unlikely it was the cause of the dead magnetron.
     
  3. crutschow

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    Mar 14, 2008
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    Gravity near a black hole may affect Magnetron operation but not gravity on earth. ;)
     
  4. cmartinez

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    Unless of course, you drop the thing and earth's gravity shatters it against the ground... :D
     
  5. ian field

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    When I fixed those things for a living, shorted magnetrons weren't totally rare.
     
  6. nsaspook

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    Posted to the Internet on how gravity affects a Magnetron. (sic)


    The microwave energy has a mass equivalent that generates gravity, so a giant microwave oven would suck the black hole in it, warp space and generate gamma waves that would cook the microwave killing the Magnetron.
     
  7. Kermit2

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    horizontal or vertical polarization will have no effect on cooking efficiency. if the maggie just radiates into open air and is aimed at the reflector the it should work fine whatever the polarization. such things matter when using waveguides that are completly closed for such things as radar and deep space radioastronomy
     
    cmartinez likes this.
  8. cmartinez

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    :eek:
     
  9. crutschow

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    Now why didn't I think of that? :cool:
     
  10. ian field

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    You'd need a quantum singularity to power it.
     
  11. cmartinez

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    I've got a singular neuron in my brain dedicated to trying to understand all this... :confused:
     
  12. nsaspook

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    but ...
    You simply add minus infinity to plus infinity to create the ZPE field and extract energy from it but ...


    To the OP, be careful with those magnets if you disassemble the Magnetron.
     
    Last edited: May 29, 2015
  13. bertus

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  14. ian field

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    I wanted to see what the cavity block looked like - you should've seen the state of my knuckles by the time I'd chiselled it open!
     
  15. ian field

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    Those magnets make good swarf trap oil filters.

    My last motorcycle was so far gone, the filter cartridge was clogged and started to collapse. A few zip ties round a ring magnet to hold it centered in the filter housing, Even thicker engine oil was no longer enough - I had to fill the sump with molybdenum grease.
     
  16. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
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    Ian, Anyone else,

    Any insights on what might make a magnatron short out?

    I've only seen a few in the years I've been working with them.

    One had a broken magnet, this one did not.
    And since it was a new unit, there weren't any Critters inside.

    Thanks,
     
  17. ErnieM

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    Apr 24, 2011
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    My last microwave sucked down a micro black hole which shorted out the framistan from the fibulator down to the float valve.
     
  18. BR-549

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    Gdrumm,

    If it's new, file a warranty claim.
     
  19. ian field

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    Structurally, the magnetron is very similar to a thermionic diode - its the magnetic field and the cavities around the anode that make it do more than just rectify. AFAICR: its directly heated, i.e. no cathode sleeve - the heater can break and spring out to touch the anode, or possibly get deformed by mechanical shock. Presumably any cathode coating that flakes off could also bridge the narrow gap and cause a short. If the heater isn't open circuit, you could try clearing the short with car battery current - what have you got to lose?

    Some of the Philips models have the waveguide feeding into the bottom of the compartment, which has a dielectric ceramic floor.

    This one was a rescue from the tip, so I had to repair it first. The usual test is put a mug of water in it and see how long it takes to boil, so I was a bit surprised at the sizzling and smell of cooking.

    In the compartment under the ceramic floor where the waveguide emerges, it was packed solid with maggots.
     
  20. Gdrumm

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    Aug 29, 2008
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    When I said new, I meant to say unused. I think it was actually manufactured a few years ago, and when it failed, someone put it in storage, and then my friend bought the storage locker at auction, and that's how I got it.

    Ian,
    Thanks for the explaination, though it's somewhat over my head right now, I will study it.
    I am seeing a burnt spot ( a black blister) where one of the HV leads connects to the magnatron.
    It looks like it shorted inside the epoxy, or whatever that material is that seals the plug where the two HV wires attach.
    When I checked it with my meter, everything I checked was going to ground.

    I appreciate the feedback.
    Can you explain the bit about a car battery in greater detail?
    Or tell me where I can read something about that?

    I've never come across maggots, but roaches love to hang out in these things.
    I've gotton to where I can recognize a "buggy one", by the droppings and such, before I ever take the cover off.
    Some folks just don't keep a very clean Kitchen I guess.

    Thanks again
     
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