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Registered Member #53
Joined: Thu Feb 09 2006, 04:31AM
Location: Ontario, Canada
Posts: 638
I have a small DC brushless fan in a stereo reviver that is emitting a very loud and high pitch whine. I will replace the fan later but for now I am wondering where does the noise come from? I have googled and the only info I have found tells me that the fan is defective and should be replaced. The whine changed pitch depending on what mode the reviver is in (and thusly the power drawn from the PS changes). The fan seems to make the least amount of noise when it is spinning the slowest but that still doesn’t explain (to me) what exactly makes the noise.
If any one knows what is the source of the noise it would help me scratch a brain itch.
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141
Probably the worn bush bearing(s), ball-bearings don't usually make this noise. If you can get a drop of oil on the bearing the noise will go for a while.
Registered Member #53
Joined: Thu Feb 09 2006, 04:31AM
Location: Ontario, Canada
Posts: 638
The noise is not bearings and is not comeing from the speakers. It is an electrical noise that can be heard directly from the fan. Like the noise that a push-pull flyback driver makes when no arc is being drawn.
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Bad bearings can make horrible squealing and screeching noises. I believe it's a kind of chaotic mechanical oscillation. The fan always spins slower than usual.
You say it's not bearings though, so that leaves faulty electronics. I guess they could oscillate in the audible range. If the fan speed is controlled by some kind of variable voltage circuit, that could have gone unstable. I designed a couple of variable speed fan circuits, and they all needed a big electrolytic capacitor on the output to stop strange noises coming from the fan. Maybe that capacitor in your circuit has dried out and stopped working.
Registered Member #53
Joined: Thu Feb 09 2006, 04:31AM
Location: Ontario, Canada
Posts: 638
I was about to ask you if putting a cap across the fan might take out the noise but you beat me to it, thanks. The fan is in a KS5192 stereo and it seems that this fan noise is a reoccuring issue with that unit. I will most likely replace the fan but if a big cap would remove the noise that might be a little easier of a solution.
Registered Member #53
Joined: Thu Feb 09 2006, 04:31AM
Location: Ontario, Canada
Posts: 638
Well I'm an idiot. alothough the fan is making the noise worse the sound seems to be comeing form a HF x-fmer in the power suply. Thanks for your replies.
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DC brushless fan "whine"
