I have this microwave and when I turn it on it makes an awful smell and will not heat. What can it be? The transformer or the magnetron?

follow the next steps , use the VOM and fix it. God bless you

Diode

The high voltage diode converts the A/C power output of the transformer to D/C, doubling the voltage to nearly 5,000 volts. This high voltage powers the magnetron which emits the energy that cooks the food. If the diode burns out, a lower A/C voltage reaches the magnetron, which is not sufficient to power the magnetron. When the diode fails it is often visibly burned out. If it appears to be good, it can be tested with a volt-Ohm meter capable of testing diodes. High voltage diodes frequently fail and are one of the most common points of failure in a microwave oven. A regular meter with a diode checker will not work to check these diodes. You have to use a meter with a 9 volt battery or put a 9 volt battery in series with the diode to check it.

Door Switch

If the microwave does not heat, one of the door switches might be defective. Microwave ovens normally have three door switches, if any of them fail the microwave does not turn on and does not heat. Check the switches for continuity with an Ohm meter.

Magnetron

If the microwave oven doesn't heat the magnetron tube might have burned out. The magnetron uses high voltage, high current DC power to generate the microwave frequency that cooks the food. If the microwave oven is turned on when it is empty this can cause the magnetron to burn out. Once it is burned out it has to be replaced, it's not repairable.

High Voltage Capacitor

If the microwave doesn't heat the high voltage capacitor might be defective. The high voltage capacitor works with the high voltage diode to convert the output of the transformer to DC voltage and to double the output voltage. If the capacitor is burned out the entire high voltage circuit stops working properly. The high voltage capacitor can be checked with a special VOM meter which has a capacitance testing capability. Be aware that the high voltage capacitor can retain a charge of more than 3,000 volts and can injure or kill a person if not handled properly. Only trained technicians should perform this type of testing.

High Voltage Transformer

If the microwave does not heat, the high voltage transformer might be burned out. Microwave ovens produce a very high voltage in order to power the magnetron antenna, which emits the energy that cooks the food. When a high voltage transformer fails it will usually arch and have a burning smell.

Thermal Fuse

If the microwave doesn't heat the thermal fuse may have blown. It can be tested for continuity. Watch our fuse testing video for more information.

Thermoprotector

If the microwave doesn't heat the thermoprotector may have tripped. This is a safety device to prevent the microwave from overheating. It can be tested for continuity to see if it's blown.

Main Control Board

If the microwave doesn't heat the main control board may be defective. This is not common. When a microwave doesn't heat the problem is usually a faulty door switch or within the high voltage circuit; either the high voltage capacitor, diode, transformer or magnetron.

Sound like a magnetron go to bad; here are the steps we took to replace it

Warning: You are not an electrician or repairman, following steps are from my experience. You should be careful while handling capacitor and other parts.

Unplug Microwave at least few hours before
Remove Microwave from above oven range by somebody holding Microwave from ground unscrew the screws from cabinet
Remove top cover of Microwave
Make sure to keep screws correctly in a place you remember what goes where
Make sure capacitor is discharged, GE manual inside Microwave says capacitor will discharge within 30 seconds once it is off. As a precaution check the voltage in capacitor to make sure there is no electricity
Remove other panels around magnetron part
You need to remove lot of connecting wires, should be careful to note down what goes where
If possible take digital photos to refer back when you put everything back together
You may need to remove transformer to easily remove and replace Magnetron. If you can't remove Magnetron easily then remove bottom panel of the Microwave and remove transformer
Now it should be easy to remove magnetron
Replace new magnetron and screw it. We had to put one outside part from old magnetron to new one because new one was missing that. Check to make sure both old and new one are exactly the same
Make sure put all wires properly back
Now put transformer back and screw it
Put capacitor panel in place and screw it
This might be a good time to test the Microwave to make sure it works fine now
Now cover the top panels and start to screw everything
Once everything assembled put the Microwave back above range put screws from top




Microwave Front and inside




Magnetron and transformer




Magnetron cover

Hope this helps (remember to rating this free answer).

The loud noise and no heat means that the magnetron has failed. It the part that generates the microwaves that heat the food. When it fails it shorts out, causing the transformer to heat up. That is what was causing the burning smell. The cost of a replacement magnetron is around $130-150 range so it may not make sense to have it fixed.

What is happening is that the magnetron is shorted, causing the high voltage transformer to overheat. That is what you are smelling is the insulation getting hot. When the magnetron shorts out, it makes a loud buzzing sound. Replacement magnetrons costs almost as much as a new oven so it rarely makes sense to fix.

MOST LIKELY YOU HAVE WHAT IS CALLED A MAGNETRON THAT HAS FAILED... IT IS THE PART THAT DOES ALL THE HEATING ...YOU DO ALSO HAVE A HIGH VOLTAGE TRANSFORMER THAT SEND POWER TO THE MAGNETRON BUT IT SOUNDS LIKE A MAGNETRON.... to be honest with you unless you are servicer it normally cost more to repair and for a few dollars more you can purchase a new one..... good luck to you.....

might just be magnetron and diode and thats not to terrible cost wise but if the smoke is real heavy the transformer may be burned as well and its not worth it then. mag & diode price with labor should only be $150-180 and add on an extra $120 for transformer

The most common problem would be your magnetron. Check your purchase date, magnetron's usually have a five year warranty. Not a part I recomend trying to fix yourself (high voltage ).

A burning smell along with a different sound (growl) USUALLY indicates a breakdown in the High Voltage Side. This is not a direct short (short circuit) or the line fuse would have blown shutting everything down. The High Voltage Side is made up of-- The Secondary ,or High Voltage Side of The High Voltage Transformer, A High Voltage Diode, A High Voltage Capacitor, and The Magnetron. If The High Voltage Transformer is the problem it will smell like a florescent light ballast burning, and will smell each time you turn on the MW. A HV Diode burns and opens, thus no more smell. A HV Capacitor usually does not burn nor does the Magnetron. There is no Cheap-Fix unless you can see that the HV Diode is burned into and you can get to it to replace. CAUTION: Always unplug from power before attempting to repair. NOTE: If you replace a Diode make sure it goes back in the same direction it came out. Yes there is a front and back.

buy

This is going to be either the high-voltage transformer, the magnetron, or the high-voltage diode. Magnetrons are the mosty common failure in these, and there is a campaign underway to replace "underperforming" magnetrons. To see if yours is one of these, visit: http://www.microwavedisplay.com/ge_mw_mag_kit_bulletin.pdf