From: Rob Ward <wards_at_paradise.net.nz>
Date: Fri, 28 Dec 2001 20:54:52 +1300

If you can hear the whistle with the vol right down, then it is probably a
switching regulator. Ofter the chokes (inductors) on these whistle at maybe
5-10kHz, but as you say, the whistling disappears as the load increases -
this is because the duty cycle (or sometimes frequency) changes as the load
varies. What voltage do you need to drive the HDD? Is it 12V?

Rob


----- Original Message -----
From: "Tjerk Schuringa" <regenpak_at_yahoo.com>
To: <jukebox_at_cool.haxx.se>
Sent: Friday, December 28, 2001 2:52 AM
Subject: Re: Getting rid of that damn noise.


> I observed two things about the whistle: it is also present with the
volume all
> the way down and it does cease when the HD spins up in my newish (used to
be
> heehee) unit. I haven't looked at the schematics yet but it could be that
one
> of the voltage inverters (there must be several!) that feeds the HD goes
into a
> sort of "burst" mode which is about 1 kHz (that irritating whistle) and
goes to
> an ultrasonic frequency when the HD draws current. It's likely to be a
messy
> mod in any case!
>
> T.J.
>
> .
> .
> .
> .
> .
>
>
> __________________________________________________
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Received on 2001-12-27