Humming buzz, then the fuse blew.

Hi @beanman56

Humming, buzzing sound could be a few things.

Was the turntable rotating before the fuse blew? If not it could have been a faulty turntable motor. Same with the fan.

I can't find the schematic for the oven (GE 31-30856) which would have helped. Sometimes it is tucked up inside the oven near the control board. Worth a look perhaps as it would make things easier.

You would really need to test all the components that need AC power to work i.e. fans, motors, HV components (transformer, diode, capacitor, magnetron) to check if they're OK or not as it could be any one of them, especially since it occurred whilst is was operating.

Here's a link that may help with this.

If it had happened when the door was first closed and/or when the oven was started, my first thought is that you check the door interlocks as they are mostly the cause when it happens then. Although in saying this if one was loose then I suppose it could have happened whilst the oven was on.

Here's a part list that is also useful for when you find the faulty part. Find the part in the list to find the manufacturer's part number (not the supplier's part number) and then search online for that number to find suppliers that suit you best.

Be safety aware when working in microwave ovens. The HV capacitor can store >5000V DC for months even if the power has been disconnected for this length of time. This amount of voltage can seriously injure you. The HV capacitor needs to be correctly discharged as soon as it can be accessed after the oven's cover has been removed and before commencing any further work in the oven