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microwave high voltage ?s

Discussion in 'General Electronics' started by JamesgangNC, Jan 11, 2005.

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  1. JamesgangNC

    JamesgangNC Guest

    Working on a ge microwave. It does every but heat. The high voltage diode
    tests open in both directions with my meter. I've never tested one of these
    puppies before. Can I assume it tests just like an ordinary diode?

    From the sound I'd say the hi voltage transformer is working. Windings
    check out ok with meter as well as the filament in the tube seems ok.
    Getting about 85 ohms from the filament connections to the metal case of the
    tube. That's another one I'm clueless about, don't know if that's good or
    bad?

    Thanks in advance for any advice. I've got some regular electronics
    experience but never fooled around with a microwave before.
     
  2. Jerry G.

    Jerry G. Guest

    You cannot test the HV diode with your meter. Your DVM would never have
    enough break-over voltage to get the junction to properly conduct.

    It is best to use a proper HV diode tester to check this type of diode. The
    safest testing if you do not have the proper test gear, such as the HV
    probe, microwave radiation checker, and etc, is to use parts substitution.

    It is possible that any one or combination of parts can cause the microwave
    to not function properly.

    --

    Jerry G.
    =====

    Working on a ge microwave. It does every but heat. The high voltage diode
    tests open in both directions with my meter. I've never tested one of these
    puppies before. Can I assume it tests just like an ordinary diode?

    From the sound I'd say the hi voltage transformer is working. Windings
    check out ok with meter as well as the filament in the tube seems ok.
    Getting about 85 ohms from the filament connections to the metal case of the
    tube. That's another one I'm clueless about, don't know if that's good or
    bad?

    Thanks in advance for any advice. I've got some regular electronics
    experience but never fooled around with a microwave before.
     
  3. Diode has a voltage drop of 6 volts or more in the forward direction. Can't
    test with meter. Need power supply and resistor.
    Something shorted, probably the magnetron. Filament to case should be
    open.
    See the Microwave Oven Repair Guide at the site below, expecially the
    SAFETY info.

    WARNING: Microwave ovens are by far the most dangerous consumer electronic
    equipment to repair and it's not mainly the microwaves but the very lethal
    voltages inside.

    --- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/
    Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
    +Lasers | Sam's Laser FAQ: http://repairfaq.ece.drexel.edu/sam/lasersam.htm
    | Mirror Sites: http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html

    Note: These links are hopefully temporary until we can sort out the excessive
    traffic on Repairfaq.org.

    Important: Anything sent to the email address in the message header above is
    ignored unless my full name is included in the subject line. Or, you can
    contact me via the Feedback Form in the FAQs.
     
  4. JamesgangNC

    JamesgangNC Guest

    Thanks for the info everyone. If the tube's shorted then the diode might be
    gone too. Guess I could test it with 110v and a light bulb. The
    transformer makes enough noise to sound like it's under a load. Looks like
    magnetrons are $60 or so. Probably not worth it for this 12 year old
    microwave. Really nice faq on microwave repair. I was wary of the hiv
    section to begin with having dealt with them on tv's and I figured to be
    1000 watt microwave means that there has to be a fair amount of current to
    go along with that voltage.
     
  5. TeleTronic

    TeleTronic Guest

    If you have an analogue meter with a battery of over 6 volts,discharge the
    cap,disconnect one wire from diode,set ohms to highest range
    connect leads across diode.Reading in one direction{over 50k]inf.in the other.
    Filement to mag case should read inf.
    A defective diode can cause the capacitor to become hot.
    Also test the cap on a high Ohms range[Analogue meter] you should get a needle
    kick and slow decay.You can't test with digi.meter.
     
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