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Its the transformer I just had two with the exact same failure . No sound when hitting start just popping the house breaker and blowing the internal fuse. I thought the same as the rest that it was the capacitor because that is usually the suspected component but nope not on the frigidair ffmv164lsa and also on the kenmore 79080323310 made by frigidair with the same parts inside. Same Mag cap and diode same transformer both had a shorted to ground transformer!!
Just about all MW ovens made in the last 15 years are almost identical inside and operate in a similar manner. Most have a service sheet packed inside that will contain basic troubleshooting tips. If your having trouble with your oven, first remove the top and sides cover. It will be secured with security TORX screws. Now slide cover toward the rear.
First, does the interior light and control panel display come on? If not check the 20amp slow blow fuse located near where the power cord enters the cabinet. If bad,replace.
Next if the oven gives every indication that it is cooking yet does not actually heat your food, then check for 110V at the large power transformer. If no voltage than check the three micro-switches that are part of the door latch interlock. Failure of one of these switches is very common. If the 110V is present and yet unit does not cook and/or unit makes a loud vibrating noise, then the problem could be the magnetron, diode, or capacitor. WARNING: There is over 2000V in this circuit. Even when unplugged the capacitor could still hold a charge. Discharge cap by using a screwdriver and short across the two terminals. There is an internal bleeder that should take care of this but discharge the cap just to be sure. The diode can be checked by using a 9 volt battery to bias the diode on. Note: The diode function on your multimeter can not be used in this instance. The Capacitor can be checked by using an ohmmeter seeing if you see a surge as the cap charges. Reverse leads to check again. There isn't an easy way to check the Magnetron but arcing in the cabinet and/or a very loud buzzing are indications that one has failed. Mags are not normally replaced due to cost, about $75.
The fuse can be replaced, but the underlying issue should still be investigated and resolved. Otherwise the new fuse will blow also.
If the microwave is not working the thermal fuse may have blown.
When a microwave stops working the problem is usually the line fuse or within the high voltage circuit; either the high voltage capacitor, diode, transformer or magnetron.
Its tripping a high limit most likely. Be careful there is 2100 to 4000 volt high side with a capacitor if its not an inverter. The standard components consist of noise board, fuse, touch panel and power controller, high limits, door switches, whipper motor, fan, transformer, capacitor, transformer, magnetron, diode, plate rotator.
Discharge cap (for safety and further testing)..
Test fuse; if fuse tests blown test door switches first.
Test limits.
Check amp draw with slow blow fuse; open door to stop unit and again discharge capacitor.
Test resistance to ground on whipper, fan, magnetron, light.
Test resistance lead to lead (measurable on motors/coils/magnetron).
Test capacitor in ferrads, compare to spec on print.
Check diode forward and reverse.
Test output voltage from power control board to transformer.
Test transformer coils.
Best of luck and play safe; dont test voltage output from the transformer, voltage at capacitor or magnetron.
several of the GEs i have worked on with your symtoms turned out to be bad magnetrons ... if the magnetron gets too hot then it will go bad .. you can get it really hot by running it without anything in the oven .. but several of the failures were caused by a fan mount failure ... there is a fan that cools the magnetron .. it is mounted on a plastic framework .. if the plastic breaks or distorts then the fan is not aimed in the correct direction .. the air goes around the magnetron instead of thru it and it fails to cool the magnetron ... so in these cases the fan framework was repaired and a new magnetron installed .. often that repair costs more than a new microwave oven .. there are other things that will cause the same trouble .. a high voltage diode, a capacitor, a transformer, a relay and a high temperature cut out switch ... the cutout automatically resets once things cool down but it can go bad .. the cost of some of these things is not high but labor often dictates the repair vs replace decision ... magnetrons cost a lot unless you have connections .. .at any rate you dont want to be powerering the microwave when its taken apart .. with the cover off there is potentially fatal voltage and current avalible by just touching the wrong thing .. ..
If the diode is NOT shorted or burned looking, it's probably fine.
There should also be a "mini-manual" hidden inside the unit behind the control
panel or hidden on the left side behind the grille, which is very
helpful when troubleshooting, & testing.
It has a wiring diagram and a schematic which shows you how the components are connected. On one terminal of the high capacitor, there is only one connection - to the high voltage output of the high voltage transformer.
The other terminal of the capacitor will be connected to the high voltage diode and the magnetron, as well as one of the heater (cathode) windings of the high voltage transformer.
You could have a bad capacitor or diode. If the cap is open or the
diode is closed or both, then this could be the problem. You should get
a reading on the cap but not on the diode. If the diode fails then you
will get a reading. The capacitor stores the energy being produced by
the transformer while the diode makes and breaks that connection about
a billion times per second. This causes the magnetron to agitate the
molecules on whatever food or bev you have in the oven. The constant
agitation produces friction, friction produces heat.
Plus the back is on with some special screw. Looks like a star screw
hole with a center pin to keep out anything but a special bit.
A hollow point star drive is what you need for them screws.
Getting a reading is another way of checking to see if we have an open
circuit. Electricity cannot travel along an open circuit and therefore
the appliance won't heat. This diode and this capacitor are 2 of the
toughest stumpers known to mankind when comes to testing them. The
capacitor could have simply seperated internally and died (I think that
is the problem by the way) But the diode may be faulty as well. If the
capacitor was shorted then the fuse would be blown. But the microwave
runs so it is probably open. Their are several hi limit fuses built
into this microwave beyond the power supply. One is hidden way on the
backside of the cabinet follow the wires to it. If it is open then the
mag(magnetron) aint getting power. The Mag has a fuse mounted on it as
well. If the mag itself is open ther will be no heat. Look at the tower
on the mag. If it has a hole in it then it is the mag. If the leads to
the magnetron are shorted to the mag then it won't heat but the fuse
will blow. So it probably AIN'T the mag. Take a note of how the cabinet
screws come out. Put the long one in the same hole when putting the
case back on or it won't run. These tricky dudes put in a switch which
gets pushed against by a long screw and it is all hidden
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