• ** REMEMBER! **The microwave can still shock you even unplugged!!

    ALWAYS discharge the high-voltage capacitor first if you even think your hands will come close to any HIGH VOLTAGE components.

    Jeff mentions this: Anything in the high voltage ( magnetron, capacitor, diode, wires to and from ):
    ...Use a metal ( not the shiny chrome type ) screw driver with a insulated handle to short across ( touch both at the same time ) the terminals of the high voltage capacitor to discharge it.

    From Jeff's site: http://www.applianceaid.com/component-testing.php

  • Please note, some of the links on our site are affiliate links (Learn More)
  • Important Announcement

    It's with sad news to announce that our site owner, Jake, has passed away. You can read the details here.

Breville Microwave BMO734XL Loud Humming and Not Heating this morning


Premium Member
Mar 12, 2005
Whitby, Ontario, Canada
Model Number
6-10 years
We had this microwave for a long time after acquiring it at a charity silent auction years ago. LOVE IT. Now it is dead :cry:. Everything seems to work normally except for the loud noise and no heat. Reading other posts, the different sound and the non-heating means the magnetron needs to be replaced. Now...I would test the related parts (transformer, capacitor, etc.) to be sure.

However, I can't even come close to finding core parts for this microwave including the magnetron. This site and the AppliancePartsPros site does not have Breville as manufacturer! I am wondering if another brand's magnetron will work in this machine. I know Breville is an Australian but the parts are made in China.

The consensus of advise out there suggests I should not even try to repair it and just buy a new one. Anyone who has read my past posts and those who have helped me here (including Jake!) knows that this is not the way I like to operate. We are all here to take the risk and make an otherwise perfectly working assemblage of electronics and metal out of the landfill.

A copy:

Q - The microwave makes a loud "hum or buzz" noise but will not heat up the food?

A - 9 times out of 10 this is usually this is a bad magnetron, the other time is sometimes a bad high voltage diode. See components section.

Written for a GE, but same idea for testing to see if the unit is creating high voltage...

I can't even come close to finding core parts for this microwave including the magnetron.

If it comes down to the mag...give us the numbers off of the mag and we can see what we can find.

jeff sr.
Thank you Jeff Sr. In the GE instructions it says: "This will work on all microwaves with a transformer and diode system ( not the inverter style )." This microwave says "Inverter" on the front door!
Could I just take the chance and replace the Magnetron? I read somewhere the magnetron lasts about 2,000 hours. it is about 8 to 10 years old. Realize it is expensive, but it is a high-end oven and I could give it to my son if it fixes it.
So update: It does not say inverter on it! I was thinking of the Panasonic at work. I opened it up and discharged the capacitor - no spark but it has been unplugged for two weeks. It has a transformer, diode and capacitor. So I guess I will start to test. There are two test protocols the one you send and on on the forum pinned post.

capacitor and diode.jpg Magnetron.jpg Transformer Cap and Diode.jpg
By the description it sounds like a defective magnetron
Thanks! even though my father was an electrican, all the warnings have me freaked out. (plug it in run for a few then short the capacitor...Spark?) Don't worry, I will test and get back. The transformer continuity is there, so I think I am generating HV.

Users who are viewing this thread

Support Our Site

If you feel that you have benefited from this site, and would like to show your appreciation, please consider making a donation.