Loud whine near end of preheat

Hi everyone,

Since about 5 roasts ago, I’ve started hearing a loud whine sound start up towards the end of preheat. Once out of the last 5 roasts it didn’t occur.

It’s not a mechanical, metal on metal sound as far as I can tell, but more like a noisy fan or an inductive load noise. It’s loud enough to hear it all through the machine (the drum is very much like a soundboard!)

Once the sound starts, it can’t be stopped by cycling through the modes. This last time it started before I charged so I cycled through the modes a couple of times, returning to preheat.

It doesn’t seem to affect the roasts, everything continues as expected in all other ways.

I haven’t paid attention to when it stops, will do that next time for sure.

Here is a link to a 30 second mp4 file, the noise starts at 18 seconds.

Thanks for your feedback!

Does this happen only during pre-heat?

Have you tried to run the roaster cold and see if it happens at all ?

Can only suggest the usual suspects
fan clearance from the backplate, I use a couple of coffee stirrers as a pseudo feeler gauge
chaff basket correctly seated in the rubber seal?
drum belt or pulley slipping?
Drum motor loose?

All the best

Thanks, I’ll check those. It’s such a resonant whine, not at all like metal scraping. I’ve had the chaff basket rubbing, this is quite different. I’ll also do some more testing and keep this thread posted.

Ok, so was able to do a few more roasts, and try out a few things.

On the first roast, I didn’t wait to the end of preheat - I manually pressed MODE to start charging at about 15 minutes into preheat, before the sound started. I completed the roast and let the Bullet go into Cool then Shutdown on its own. The noise never presented itself.

At 88C, I started preheat again, this time letting it finish preheat fully, and no noise! I completed the roast and let it go into shutdown again.

At 177C, I started preheat again, again letting it preheat fully. At 18-19 minutes of preheat, just before declaring “Charge!”, the noise presented itself, but fainter than usual.

It’s super loud if I put my ear on the side of the control panel, and seems that this is where the noise is originating. Putting my ear on a leg, or on the back chaff collector the noise is much fainter.

So it really seems at this point that the noise is coming from the control pod itself.

I’ll repeat the tests, but at this point, I do worry that there is something amiss with my machine. It’s not currently affecting operation, but nonetheless, I worry.

Would it make sense to take it to Sweet Maria’s from whom I purchased it (it’s an hour drive away) and have them look at it? Other thoughts?


The potential source for noise in the control panel is the IBTS fan. That fan (assuming it’s running at the proper speed) is at 16,000 RPM. I would expect it to be more of a scream than the low freq which the audio clip has. So perhaps the IBTS fan is not running at 16,000 rpm. You can see the measured fan speed in the Info panel when the roaster is running e.g. during Preheat. ( Click the “i” button upper right on the Roast screen. )

Failed IBTS fans are not unheard of- I had to replace mine at 4 mos. It was defective from the start but only showed up when a test was added to the f/w in 2019. I believe the fail point at that time was 5,000 rpm but that may have changed in the subsequent 3 yrs.


That my friend, is an awesome bit of feedback - thank you very much!
I’ll investigate further - thanks again!