20 in Box fan has secondary hum

Hi @loninappleton

Does the sound occur if you manually rotate the fan blades?

Thanks for answering.

I wanted to ask before I took the new one's grille off. But I have another of the same brand I've had for so long I've fixed the handle that fell off. It does not have the secondary hum or at least not to any degree. That's why I thought there might be some hack for the blades. I'll take the grille off the new one and see if it's hitting anywhere but I cannot see any obstructions. Will report back anything I noticed.

@loninappleton

I was thinking more of an electrical motor hum. Sometimes poor design of the motor windings can generate a humming noise when operating, that's why I suggested doing a manual spin test

If the noise is still there when manually operating the fan it could be a mechanical issue e.g. bearings, shaft alignment etc

I haven't taken the grille off yet but, you see, I get this secondary whine which many are familiar with from PC fans b/c they are small. I have only one of three 20 inch fans that _doesn't_ do it-- an older one. I had another idea on this and I'll come back if it's worth anything: I wondered if the front grill itself can be making the noise-- if there had been a manufacturing change. Since I recently had a newer one just freeze up at the motor; I kept some of the parts and disposed of the rest at the metal recycler. I save the grilles so could try some things that way.

If it was motor hum, no one could hear it as the fan is running.

This seems like a trivial project but if solved could be used by others so it's worth pursuing for me at at least.

Another thing I've seen on Youtube is using a penny on one blade to get rid of wobble so there are some hacks with this. :-) I've repaired chipped blades as well.