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Sharp microwave oven problem

Discussion in 'Electronic Repair' started by Pat, Nov 16, 2004.

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  1. Pat

    Pat Guest

    My Sharp convection microwave (model R-9H66) trips the circuit breaker
    everytime it's turned on. It started doing this after its door was slammed
    shut by someone. It's obviously shorting somewhere when turned on, and I
    took the outer housing off to look at the wiring to see if there was
    anything obvious,but didn't notice anything.

    Does anyone have any idea what might be wrong or what to look for? It was a
    fairly expensive unit when I bought it 6 years ago, and I'd hate to just
    through it away, especially if it turns out to be something relatively easy
    to repair.

    Thanks for any help. I appreciate it.

    Pat
     
  2. Bob Shuman

    Bob Shuman Guest

    I'm not familiar with your model or unit, but there are safety interlocks on
    every microwave to assure the door is properly shut to prevent radiation
    leakage. These usually come in two flavors, a normally open microswitch
    that gets closed to "make" the connection to power the magnetron, and a
    second normally closed microswitch that is normally shorted across the
    magnetron and opens when the door is shut.

    These two switches work in combination and if all works properly, the short
    is removed and the power is then applied. In your case, I'd look at the
    switch and the alignment to make sure the one that opens is in fact opening
    properly. Sounds to me like it may have been jarred and is no longer aligned
    properly so stays closed creating the short and blowing your breaker (most
    units I've seen have a 15A slow blow fuse that goes first before the
    receptacle breaker).

    Good luck and hope this is helpful.

    Bob
     
  3. Jerry G.

    Jerry G. Guest

    Check for defective safety switches, and replace as necessary. It is rare,
    but there may be a short in the power supply, or the HV section.

    Take care that these are extremely dangerous to service yourself, unless you
    really know what you are doing. As for replacing the safety switches, use
    the origional manufacture parts only, and make sure you know how to adjust
    their placement. Check for the proper tollerance of how the door seats, and
    that the play in the hinges is correct.

    After replacing any components, especialy around the door area, it is
    strongly recomended to take measurments for any possible radiation leakage,
    in case the door may not be seating properly. If the door has been slammed
    so hard to damage the switches, a radiation leakage test would be in good
    order.

    I would recomend that you take the unit to an authorized service center
    where they service microwave ovens, for proper and safe service, unless you
    are properly trained, equiped, and are experienced in this type of service
    work. The microwave oven is the number one dangerous appliance in the home.
    The next ones down are the TV set, and the computer monitor.

    As for microwave radiation, at low levels this is not able to be felt, but
    damage may be done to anyone within its range. There are numerous safety
    articles about this. http://www.fda.gov/cdrh/consumer/microwave.html
     
  4. dkuhajda

    dkuhajda Guest

    FYI: I Never work on Microwave ovens. They simply are not worth the
    trouble or RISK to me. Realize that the capacitor in a microwave oven
    stores a charge roughly equivalent to the LifePak defibrillators we are
    seeing advertised on tv. If you get across it the wrong way with it
    charged at the wrong time in your heartbeat, boom, your probably dead
    unless medical help arrives in a few minutes, at a minimum you just did
    damage to your heart. That would be during the T wave of your EKG.

    At the very least, everyone I know who works on microwave ovens now, has
    insulative gloves up to the elbows on at least one arm AND double checks
    the high voltage stored on the capacitor with a high voltage probe.

    My suggestion, pay someone the $50 labor to work on it for you. If someone
    really does not know exactly what they are doing and is willing to accept
    the risk, $50 or so, is simply not worth the risk for the average Joe
    owner.

    David
     
  5. Art

    Art Guest

    Read the RepairFaqs regarding these infernal machines before even attempting
    service. There are many posts to Sam's Site within this and other
    newsgroups. As stated, these can be EXTREMELY DANGEROUS to service for the
    un-informed. Occasionally LETHAL!! BTW, I agree that it is highly probable
    a defective or miss-aligned switch, exp since some how "the door had been
    slammed"!!
     
  6. And if the oven is unplugged, working around the area of the door switches
    is safe. However, you do have to know where that is and where NOT to go!

    --- 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 is ignored.
    To contact me, please use the Feedback Form in the FAQs.
     
  7. Ken G.

    Ken G. Guest

    Now that you scared the guy to death .....


    its probably a door switch that jammed when someone slammed it . look in
    where those plastic spades on the door poke into the front there are
    some squarish black switches that get pushed when the spades go through
    the holes .
    Each switch has a little ( probably ) red nub that clicks when you push
    it in . You can reach in and push those with something to see if they
    mechanically click .
    If you do find the bad one you can unplug the wire from the back of it
    and note where they went and take the switch to some repair senter for a
    new one . Put it back the same way it came out . You dont need to do any
    of those silly tests .... those are for ovens that ha door damage .
    Just dont touch the wires coming out of a big capacitor ( silver oval
    like can mounted to the bottom or rear of the case )
     
  8. Pat

    Pat Guest

    Thanks to everyone for all the replies and warnings. I've worked around
    electronics before and know stay away from the caps or make sure they're
    discharged and everything is unplugged if I must go near them.

    If it turns out to be a bad switch (as seems likely) where's a good place to
    get a replacement?

    Thanks again. -Pat
     
  9. Bob Shuman

    Bob Shuman Guest

    Pat,

    I generally look in the owner's manual and contact the manufacturer (using
    the phone number listed or a visit to their web site) or the closest
    authorized service center. Usually you can order parts, especially the
    commonly replaced items like the microswitches, diode, HV capacitor, etc.

    Another option I've used is at the following repair web site:

    http://www.repairclinic.com/0047_6.asp

    They handle parts and provide a lot of basic troubleshooting info, assembly
    drawings, etc. for many common appliances in use today. In either case, be
    prepared to pay more than what you might expect since you are paying for the
    convenience of having the distributor stock these items and not just the
    manufacturing cost.

    Good luck and exercise caution when working on the microwave.

    Bob
     
  10. Pat

    Pat Guest

    It's fixed!

    Turns out one of the switches had been pushed slightly out of the plastic
    bracket that was holds it in place, although it wasn't real obvious until I
    looked closely. When I pushed on the back of it, it snapped back into place
    and everything started working again as normal. It must have been knocked
    out of place when the door was slammed.

    A very easy fix after all, but I would have never found it if someone hadn't
    suggested checking it.

    Thanks again to everyone. You've save me several hundred dollars. Does
    make me wonder how many microwaves end up by the curbside because of simple
    things like that.

    Thanks again,

    Pat
     
  11. NSM

    NSM Guest

    | It's fixed!
    ....
    | Thanks again to everyone. You've save me several hundred dollars. Does
    | make me wonder how many microwaves end up by the curbside because of
    simple
    | things like that.

    It's said that microwaves don't burn out, they rust out. My 20 year old one
    still works after daily use, long after I thought it would die.

    N
     
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