Buzzing when undervolting 92mm Rexus Panaflo mid speed fan

[Placid]

Greetings SPCR,

I have a Rexus Panaflo 2450 RPM mid speed fan with RPM sensor.
Model numbers: FBA0912M1BX NMB-MAT (25093) 35-705-008

I needed to swap out the noisy fan in my PSU, so I started to look for a suitable 92mm fan. I wanted to avoid ball bearings, and the fan orientation was not ideal for sleeve bearing, so I searched for an alternative. Having looked through many 92mm fans that were reasonably accessible, I decided on this one due to the hydro wave bearing and that it is the one of the few fans that were close to my airflow requirements.

After testing and using the fan, I noticed what may have appeared to be vibrations transferred to the case a first, but it turned out to be motor buzz. Lowering the voltage would cause the motor to buzz. The lower the voltage, the greater the buzz intensity, to the point that it would drive me crazy. Increasing the voltage would do the opposite. With the fan at full speed, the buzzing disappears entirely. Contrary to what we're used to, higher voltages are more desirable in this case. Have anyone who tried this fan noticed similar characteristics or did I get a bad batch?

Despite the buzzing, this fan is still a significant improvement over the original vacuum cleaner, so the slight buzzing is tolerable since the summer heat spins the fan past the extremely buzzy voltages most of the time, that is until winter arrives in a few months. I'm in need of a replacement again, and hopefully this time, maybe someone may know of a better, reasonably quiet, mid speed 92mm fan at 2500-2600 RPM.

[frankgehry]

Rexus, like scythe, is a relabeller. Scythe never mentioned that their minebea series were actually from nmb-mat's value line. Most likely, a rexus panaflo is a low spec version of a retail nmb-mat panaflo. Just out of curiousity, what is the production code? In this photo, the production code is located just above the model number.

[Placid]

The fan is inside the PSU, so I can't see the numbers at this time. I will crack open the PSU if I can get a new fan to swap it out.

[Placid]

I finally got a chance to do some maintenance in the case, and opened up the PSU while I was at it.

Here's the production code:
7F06A73 -BX

[Operandi]

After testing and using the fan, I noticed what may have appeared to be vibrations transferred to the case a first, but it turned out to be motor buzz. Lowering the voltage would cause the motor to buzz. The lower the voltage, the greater the buzz intensity, to the point that it would drive me crazy. Increasing the voltage would do the opposite. With the fan at full speed, the buzzing disappears entirely. Contrary to what we're used to, higher voltages are more desirable in this case. Have anyone who tried this fan noticed similar characteristics or did I get a bad batch?

Are you feeding the fan a fixed voltage or PWM "switching" circuit?

The Panaflo bearings seem to have problems with some PWM controllers. I'm guessing the PWM controller is cycling the voltage too slowly creating an audible buzz.

[Placid]

Take a look at this thread for more details about the buzzing. It refers to this fan.
viewtopic.php?t=50140