Celing Fan Hum

I have a ceiling fan that hums badly. Is not dimmed is running at full speed or one notch down with the pull chain. Is not a 120Hz buzz but a slow hum modulated by the blade position. In other words the hum changes cyclically around the blade circle. It is not mechanical because it stop immediately after cutting power.
Any idea on what to look for when I get it down?
Thanks
MG
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I had a fan do this and it turned out to be a loose light fixture attached to the fan that was vibrating. If your fan has a light fixture attached, I'd check that before taking the fan down. On mine, each bulb has a cover attached by three small screws. I just tightened the screws and the hum went away.
David
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Maybe the starting capacitor; especially if an old unit. In the US, the AC is at 60 Hz which is a fairly low frequency. The fan speed is likely a harmonic of 60 Hz as well.
Thunder
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slow
Sounds like the motor has a problem.
Have you checked all of the wiring? Especially if the motor is grounded?
WAG
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good question
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