Timer functions, fan works, great humming noise, no heat. Magnetron??

GE microwaves are notorious for the magnetron failing, this is what generates the microwaves. Usually the unit will make a louder than normal deep hum when running if this is the case, but not always. If you have the schematic, you can measure for 120 volts leaving the control board to the transformer, you can simply measure the line in on the transformer for this. You also want to visually note that all other functions like the countdown timer, inter light, turntable, and fan are all running when you start a cooking cycle. The monitor, and interlock switches mounted on the latch assy need to be checked for continuity too. If replacing the magnetron we always recommend replacing the high volt diode connected to the capacitor and chassis ground. Pleazer Appliance...

Excessive 60 cycle hum/vibration means a bad Magnetron. Time to replace the unit.

This clearly indicates a bad magnetron, "heats food" in most cases it is cheaper to replace the microwave oven than have it repaired, since the magnetron is the heart of the unit.

If its making a humming noise, that means the diode is bad and should be replaced. Once replaced the microwave will begin to heat again.

The diode that connects to the capacitor needs to be replaced. Once its replaced microwave will begin to heat again. (If it wasn't heating and wasn't making a humming noise, then your magnetron would need to be replaced). If you are thinking of doing it yourself and need instructions, i'll be glad to help.

Possibly a shorted relay on the main timer board?? hum coming from transformer being powered with no fan running. With No fan you can hear it hum. shorted power relay on main board.

To allow us to help you at no charge, please post a NEW question, and please include your brand name and the full model number from the tag in or on the unit, as well as the answers to these questions:

When you try to microwave are the inside light, internal cooling fan and turntable all working?

Is there any unusual noise or is it louder or quieter than normal?

A loud buzz, hum, or groan is usually a shorted high voltage rectifier diode, but a sound like gurgling into an empty coffee mug is one symptom of a failed magnetron, and yet the mag can be bad without that sound.

We have a sound clip of what a microwave should sound like when the cooling fan and high voltage section are working.

We're happy to help you with free advice and we'd appreciate your thoughtful rating of our answer.

the magnetron needs replacement my friend, although you can still heat up food but eventually it will soon fail.
appreciate your kind comment

Microwave not heating problems when the timer/controller board appears to function properly, are related to the following components -

1) Diode
2) Capacitor
3) Transformer
4) Magnetron

Sounds like you just fried your magnetron. Normally when they go bad, they make a very loud noise like what you described. The smell concerns me because you may have ruined the waveguide as well. If the magnetron burns through the protective painted surface of the waveguide, the waveguide is ruined. In most microwave ovens this means replacing the entire unit because the waveguide is not replaceable. Putting a new magnetron in a damaged waveguide will result in the same arcing and eventual failure. In addition to the magnetron, the following components are part of the same high voltage network: HV Transformer HV Diode HV Capacitor Magnetron Thermal Cut-Out Any one of these components could have also been damaged. I DO NOT recommend taking any voltage measurements inside the HV network. Potentials of over 4000 volts can be reached and make it very dangerous for the do-it-yourselfer. Taking resistance readings with the unit unplugged is strongly encouraged. If you decide to pursue a repair, inspect the magnetron tip and inside of the waveguide first. If the magnetron is melted and/or there are burn marks inside the waveguide, a new microwave may be a in order. This actually may be a better option than an expensive repair. I hope you find this advice helpful.