high-pitched noise during bootup

[Mitch Bradley]

The likely suspects are the inductors in the various switching regulator 
circuits.

They look like little black water tanks and most say 5R0R on top, but 
the one near the power input says 100PF. (you might think that to be a 
100 picofarad capacitor, but it's actually an inductor.  Go figure.)

The magnetic fields in those inductors tends to induce vibrations.

Sometimes you can stop the vibrations with a dab of glue.  Hot-melt glue 
is often effective, as is epoxy.


Dan Williams wrote:
> On Thu, 2006-09-21 at 02:09 +0200, Carl-Daniel Hailfinger wrote:
>   
>> Hi,
>>
>> I have noticed some high-pitched noise during each bootup,
>> estimated frequency is >12kHz. Sounds like a bird chirping,
>> but with a much higher pitch near the upper hearing range.
>> The sound is also quite quiet and can't be heard if any
>> fans of other machines are running.
>>
>> Could anybody verify my findings in a quiet room without
>> air conditioning and other sources of noise? This sound
>> gives me a headache and at least one other person can
>> hear it, too.
>>     
>
> I've heard something like it too, and when I commented on it to MarkF he
> said it's normal and is part of the DC electronics stepping down the
> voltage (or something like that).  Somewhat like the high-pitched whine
> you can hear from the high-voltage flyback transformers in television
> sets and other CRT-based displays.  Maybe that's what you're hearing?
> Maybe check if it comes from the area around the power plug or not.
>
> Dan
>
>   
>> I would record it if my microphone wasn't so crappy.
>>
>> Regards,
>> Carl-Daniel
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>>     
>
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