Connect with us

Microwave arcing

Discussion in 'Electronic Repair' started by [email protected], Dec 3, 2006.

Scroll to continue with content
  1. Guest

    Our 5 year old Kenmore microwave has run perfectly with no abuse, no
    metal used while cooking, etc. We have also used it to warm our plates,
    and typically we warm one, two, or three dinner plates for between 1
    and 2 minutes total. They always emerge nicely warmed, not hot but
    just right. The plates are similar to what we'd call stoneware but not
    as dense, perhaps some sort
    of clay substance made by Pfaltzgraff. This shows the exact plate but
    not the material, at http://www.pfaltzgraff.com/ca/13937.htm .

    We have warmed plates in it for most of the 5 years since we discovered
    this seems to work quite well. Today, while warming two plates, we got
    a strong arc after only a second or two, which upon subsequent test
    seems to occur behind the flexible white plastic square on the right
    side
    of the cavity (assume this is the magnetron horn?)

    We shut it off immediately and then experimented further; it appears to
    still function, warming a glass of water normally, warming a container
    of rice normally, etc. However, placing the plates back in causes an
    almost immediate arc.

    So, what's changed? Have the plates somehow become more/less load now
    (unlikely; we tried two other plates as well with the same result.)

    I'm guessing maybe a buildup of grease or residue in the magnetron area
    may have changed it's parameters somehow, to the extent that it's no
    longer 'happy' being asked to warm plates.

    Ideas? (Other than "don't do that" please...)
     
  2. ian field

    ian field Guest

    Just remove the plastic bit, but make sure not to put food in there that can
    "burst" and splatter into the waveguide.
     
  3. Guest

    There is probably a build-up of carbonized food on the back side of the
    plastic plate. Do as the previous poster said. You may or may not be
    able to clean the plastic sufficiently to put it back. The potential
    for arcing has always been there, it is just that the food build-up
    finallly broke down under the high fields that occur when the oven
    cavity is lightly loaded. That is why you are always cautioned not to
    run the microwave under no-load conditions which is about what you are
    doing when you just pout loates in there. You can still warm plates,
    just put some water in a container in the microwave at the same time.
    The water will absorb much of the energy and it will take you longer to
    heat the plates. Why not just run them under hot water for a few
    seconds?

    H. R. (Bob) Hofmann
     
  4. nucleus

    nucleus Guest

    does your operating manual suggest using a microwave oven to heat
    plates?

    a microwave oven is designed to heat items containing water. a water
    molecule is composed of a single atom of oxygen with two atoms of
    hydrogen attached at a specific angle to the oxygen atom. the
    frequency
    of a microwave oven is designed to cause the hydrogen atoms to
    vibrate, causing friction with adjacent water molecules, thereby
    generating heat.

    clays contain minerals rich in metal oxides. the metal in your plates
    possibly has been marginal in the past and due to usage, the addition
    of molecular metal particles from flatware may have caused the change.
     
  5. Guest

    I think you nailed it, Bob... there were a couple of blobs of stuff on
    the backside of the shield; easy enough to clean up with some steel
    wool and then I remounted on the reverse so the waveguide shoots
    through a different area of the material. Seems to clear up the
    problem.
    Running hot water might be an option but not nearly as convenient as
    just popping them in the micro.

    Thanks.
     
  6. Lee

    Lee Guest

    If you checked your manual, you would find that shield is NOT to be
    cleaned with anything abrasive. It is made of a compound that is part
    of the distribution of the microwaves.
    My first unit manual said that (early 80's) and the one I bought a week
    ago also said that as well.
    My first unit was a Sharp, ($1,200) and included a 9 hour cooking course
    with it. The very first night, they had a Sharp tech there that said
    any dish that contained clay was not to be used as there is always trace
    amounts of metals in clay. He also said that if any container that got
    hot in the machine when there was no food/water, should not be used.
    Why don't you email the manufacturer of the plates and ask if they are
    microwave safe. I'll lay odds the answer is NO.
    Regards
    Lee in Toronto
     
  7. Guest

    dont do that, put a cup of water on the plates when you nuke them.

    Keep the plastic bit clean to prevent this recurring.

    Dont run the machine with the plastic waveguide cover removed, as food
    splatters will enter the waveguide, this will short out, and cleaning
    it out will then be difficult or impossible.


    NT
     
  8. They don't want you to destroy it but it is just a piece of plastic that
    is transparent to microwaves.
    He's been doing it for years without incident. So, something else has
    changed. As long as the plates absorb some of the energy, it won't hurt
    the oven. That's the same thing a glass of water does.

    I'd guess there is some burnt on crud which is causing the arcing.

    --- 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.
     
  9. ian field

    ian field Guest

    You should see the items Braniac (science abuse) TV show puts in the
    microwave - on average about half the items result in the steel casing being
    unfolded back to sheets of steel! Some of the less destructive items at
    least provide an entertaining light show.
     
  10. Guest

    Nukes are nothing like that fragile. You can heat plates in them, melt
    aluminium & iron in them, or put metal foil on food in them. The
    problem is just lack of load, the plates dont absorb much, plus burnt
    muck on the waveguide entry cover.

    Contrary to myth, magnetrons are not killed by running them with no
    load, that only applied to the very first commercial microwave oven
    iirc. However it does tend to cause arcing, and that can do minor
    damage in the cooking cavity, the worst example of which is frying that
    plastic plate. Once theres carbon on that, it will deteriorate until it
    catches fire. So keep that lil cover clean.


    NT
     
  11. Guest

    Nukes are nothing like that fragile. You can heat plates in them, melt
    aluminium & iron in them, or put metal foil on food in them. The
    problem is just lack of load, the plates dont absorb much, plus burnt
    muck on the waveguide entry cover.

    Contrary to myth, magnetrons are not killed by running them with no
    load, that only applied to the very first commercial microwave oven
    iirc. However it does tend to cause arcing, and that can do minor
    damage in the cooking cavity, the worst example of which is frying that
    plastic plate. Once theres carbon on that, it will deteriorate until it
    catches fire. So keep that lil cover clean and you can cast iron in it
    in peace.


    NT
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-