Oven lost all power while running. No GFI's were tripped. No circuit breakers were tripped. I unplugged and replugged the microwave oven as it said in the owner's manual trouble shooting section. microwave still without power.

Your microwave should be on a 20 amp dedicated circuit. Often people add these later after initial construction and do not have an isolated circuit for it. If you have this on a circuit with other outlets or possibly the refrigerator, this can cause the circuit overload and trip your breaker. Try running an extension cord from another circuit that is not being used such as outlets, but not GFI outlets! and see if your microwave operates then. If not you have an internal issue with the microwave and it could be a defective Magnetron or doorswitch assy causing the problem.

the oven is short I suggest checking the capacitors and the power supply lines

The magnetron probably has a partial short pulling more current than normal as it runs, the other two items that give trouble is the high voltage diode, "sometimes cracks" to the high voltage capacitor, "usually shorts"

It is leaking to earth due to spilliage on the connections I expect.
It is not safe to use in that condition.

Hi,

Here is a tip that will help you to figure out what is wrong with your Microwave Oven....

Microwave Oven Basic Troubleshooting Tips

heatman101

from online Microwave Repair Manual: Totally dead oven (no lights, no clock, no display, no fan, no heat...)First, check power to the outlet using a lamp or radio you know works. The fuse or circuit breaker at your service panel may have blown/tripped due to an overload or fault in the microwave oven or some other appliance. You may just have too many appliances plugged into this circuit - microwave ovens are high current appliances and should be on a dedicated circuit if possible. If you attempt to run a heating appliance like a toaster or fryer at the same time, you *will* blow the fuse or trip the circuit breaker. A refrigerator should never be plugged into the same circuit for this reason as well - you really don't want it to be without power because of your popcorn!

If you find the fuse blown or circuit breaker tripped, unplug everything from the circuit to which the microwave is connected (keep in mind that other outlets may be fed from the same circuit). Replace the fuse or reset the circuit breaker. If the same thing happens again, you have a problem with the outlet or other wiring on the same branch circuit. If plugging in the microwave causes the fuse to blow or circuit breaker to trip immediately, there is a short circuit in the power cord or elsewhere.

The microwave oven may be powered from a GFCI outlet or downstream of one and the GFCI may have tripped. (Removing a broken oven lamp has been known to happen.) The GFCI outlet may not be in an obvious location but first check the countertop outlets. The tripped GFCI could be in the garage or almost anywhere else! Pushing the RESET button may be all that's needed.

Next, try to set the clock. With some ovens the screen will be totally blank following a power outage - there may be nothing wrong with it. Furthermore, some ovens will not allow you perform any cooking related actions until the clock is set to a valid time.

Assuming these are not your problems, a fuse has probably blown although a dead controller is a possibility.

While you can do some repairs on your microwave, what you don't know can kill you... even on an unplugged microwave, so make sure you understand the dangers and how to reduce them before you try anything inside a microwave. If you want to do more yourself, go to the link at the top of this post.

The first thing you need to check is the GFI--when it trips, it definitely should shut off power to the circuit. It may be wired incorrectly, or is faulty. There should be a 20 amp breaker and wiring to the oven.It is also much better is the oven is the only appliance on this circuit. Hope this helps!

There is a fuse under the cover, as well as a couple of safety thermostats that can cause a dead oven. It may also be that the power transformer for the control circuit board has failed. I've seen several Sharp ovens where the transformer died because of power surges. This would cause no display and no functions even though the oven has power. Also, did you make sure the outlet your oven is plugged into has power? If it's a GFI outlet it may need to be reset, or a circuit breaker in your electric service panel may have tripped.

Hope this helps, and thanks for using Fixya!

You might try pulling the plug on the unit and leaving it overnight. The electronics may have locked up due to irregular voltage during the failure. There may also be a GFI (ground fault interrupter) on that circuit that has tripped for the same reason. Check the kitchen outlets for a tripped GFI.

Remove unit and check trip/reset switch on unit. Double check GFCI receptacle with plug tester with GFCI test button.