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GE Microwave JVM1540DM3WW Everything but Heat

Discussion in 'Electronic Repair' started by [email protected], Apr 4, 2013.

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  1. Guest

    Everything operates correctly, except no heat. I can hear a transformer hum, come and go while it acts like it is working, like it is trying to run, but nothing heats. I understand electrical systems and have read considerable about troubleshooting and repair. I just wanted to ask before undertakingthis task. Based on the circumstances with the on and off hum, what do youthink?

    Thank you ...Ken
     
  2. Phil Allison

    Phil Allison Guest

    <>

    Everything operates correctly, except no heat. I can hear a transformer hum,
    come and go while it acts like it is working, like it is trying to run, but
    nothing heats. I understand electrical systems and have read considerable
    about troubleshooting and repair. I just wanted to ask before undertaking
    this task. Based on the circumstances with the on and off hum, what do you
    think?


    ** Do NOT even dream of fixing your own microwave oven.

    The devices are ABSOLUTELY LETHAL !!



    ..... Phil
     
  3. Tom Kupp

    Tom Kupp Guest

    Bad triac?
     
  4. whit3rd

    whit3rd Guest

    Microwave ovens have a vacuum tube. If you have a bad tube, or no
    filament power, the transformer will hum and no heat is produced.
    New microwave ovens aren't a lot more expensive than new tubes
    and the labor to put 'em in.
     
  5. Could be a bad heater in the magnetron, or the HV doubler is bad.

    I'd not suggest opening a microwave oven for repairs unless you are
    familiar with handling the high voltage cap in them. They seem to be the
    perfect rating to electrocute folks.

    If you're past that, and know how to dischard the filter cap, turn on the
    oven and check the HV output of the doubler, it should be around 4kV.

    If that's good, check the heater coil of the magnetron, it should appear
    to be a short. Check the filament winding on the transformer too. It's
    more likely to have bad crimp connections than being burned out, but you
    never know.

    A fairly detailed (even overly detailed) microwave oven FAQ is here

    http://repairfaq.ece.drexel.edu/REPAIR/F_micfaq5.html#MICFAQ_008

    Anyways, if the cap or rectifier are bad, it's worth $15 and a trip to
    ebay for replacements. They're all pretty generic and the chinese junk off
    there is no worse than they build new microwaves with anyways.

    If anything else is bad, it's just not worth fixing unless you want to
    make a project out of it.
     
  6. Phil Allison

    Phil Allison Guest

    "Tom Kupp"

    *** If the unit had a faulty triac ( most use relays ) then the transformer
    would either:

    1. Not hum at all.

    2. Blow the supply use immediately.


    .... Phil
     
  7. I promised to count the number of screws on my old (1981) samsung
    microwave oven. This was back when they were overbuilt. There's actually
    20 stainless torx screws in the front door inner bezel just to hold the
    glass in place. It's amazing.
     
  8. I promised to count the number of screws on my old (1981)
    Could their purpose have been to hold the screen so firmly in place that it
    could not come loose and permit leakage?
     
  9. the screen is behind the glass, or sheets of glass, where would it even
    slip or go? It's not like 20 screws will hold a piece of glass all that
    much flatter than 10. I've seen autoclaves with wimpier doors.

    Has anybody ever come across a microwave oven that actually has microwave
    leakage out the front door or gaskets? We always did the testing, but
    never had a reject or a loose door.
     
  10. "Cydrome Leader" wrote in message
    Could the /glass/ slip?

    The question is /plausible/ in the context that Samsung wouldn't waste time
    and money installing screws it didn't think were necessary. (See following.)

    Back in the 70s (I think) the Government set emissions standards. I remember
    an Amana commercial (I'm watching "Perry Mason" as I write this -- why
    couldn't Barbara Hale have been my mother? Of course, then I would have been
    William Katt.) in which a large, sharp-edged weight was slammed against the
    oven, leaving a huge gash. Amana claimed that, even with this damage, the oven
    still met emissions specs.
     
  11. I'd love to see what a large wedge would do to a modern microwave oven,
    other than go right though the entire thing, like a cup of to-go soup when
    the lids comes loose and it just instantly dissolves the paper bag you
    were holding just seconds earlier.

    If there were strict standards back then, I doubt anbody is testing them
    anymore. Those cone shaped Simpson probes were the rage, then there were
    the taiwanese cheapo VU meter attached to a diode and a loop of wire
    leakage meters. Again, I've never seen any of them ever register anything.

    Even the Amana and Tappan units didn't have thousands of screws holding
    them together. I've always been really curious about how this oven was
    designed or who it was copied from in the first place.
     
  12. I'd love to see what a large wedge would do to a modern
    I have a near-end-of-American-manufacture LItton that's built like a tank.
    Haven't used it in a few years, but it'll still be working when I'm dead. Only
    problem is that the cavity's on the small side.

    It's possible all those screws were needed to compensate for sloppy
    tolerances. But without tearing it apart, there's no way to know.
     
  13. I liked the ones that opened like oven doors. The last tappan around here
    died when the mechanical timer wore out.
    Interesting point. Maybe the glass is what holds the door together.

    I'm going to have to take the thing apart. The thing is guest-proof too.
    It's digital but you have to enter cooking times in this format

    [time button] [enter the time] [time button] then [start]

    it may be built around a soviet RPL calculator chipset.
     
  14. It's digital but you have to enter cooking times in this format
    It sounds as if whoever wrote the code didn't want to have to keep a running
    calculation of the number of seconds -- just do it once with the second [time
    button] press. Of course, it could have been done at [start] just as well.

    The GE Jet in my range hood has a simple and easily understood entry system.
    I'm amazed how many microwave ovens have confusing and complex systems.
     
  15. Jerry Peters

    Jerry Peters Guest

    Couldn't aggree more. When my mehanical timer microwave went a few
    years back I went around to the 4 or 5 different microwave ovens at
    work to find the one that was simplest to use, then bought a very
    similiar one of the same brand. Key in time, hit start.

    Jerry
     
  16. Guest

    But you're robbing the design engineers the opportunity to demonstrate
    how complicated a system they can design just to heat a bowl of soup.
     
  17. Leif Neland

    Leif Neland Guest

    Ian Field skrev den 05/04/2013:
    Another thing to consider is the resulting effect of the microwave.

    Using these formulas:

    1 Ws = 1J

    4.184 J for the temperature of one gram of water to increase 1 degree
    celsius (°C).

    Then take the time for 100g=1dl tap-water to boil from tap-temperature,
    perhaps 10C, it is easy to calculate the resulting effect.

    (And here you see the advangage of using metric, instead of units based
    on the length of king X's thumb and the volume of his bladder or
    whatever :) )

    Doing that, I discovered my microwave, labeled 900w, actually delivered
    250w.

    I don't know if it still takes 900w from the mains, but I discarded it
    and replaced it.

    technically, you might have called it "working" :)

    Leif
     
  18. Phil Allison

    Phil Allison Guest

    "Arfa Daily"
    ** Correct.

    A couple of things will tend to under rate the actual heat power delivered
    by a microwave oven tested with a vessel of water.

    1. An unsuitable vessel can absorb much of the energy.

    2. Heat is lost to the surrounding air during the test.

    3. The thermometer will usually under read the actual temperature rise.

    So, use at least half a litre of water in a thin walled plastic container
    and heat the water to no more than 60 degrees C.

    Be damn quick with the thermometer and even then allow 10% for losses.



    ..... Phil
     
  19. amdx

    amdx Guest

    I have a working Frigidaire microwave that was manufactured in 1983.
    The specs say 1.38 KW 120V 60HZ, a little odd, now it would be amps not
    KW. Don't know about the output power, nothing on the unit, and the
    owners manual says nothing about the power. The model number is MC800M,
    I would think 800W is to low for the output power. But, I'm curious what
    is the efficiency of a magnetron?
    Mikek

    PS. The owners manual says " If you move or sell the microwave to
    another person please report the change so we can update our records.
    Hope I'm not in trouble, I've moved 5 times without reporting. :)
     
  20. amdx

    amdx Guest

    No kidding, just give me a knob that I can spin to the minutes I want.
    Mikek
     
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