Re: Why so much HD activity?

Terry Pinnell wrote:

> Terry Pinnell <terrypinDELETE@xxxxxxxxxxxxxxxxxxx> wrote:
>
>>"J. Clarke" <jclarke.usenet@xxxxxxxxxxxxxxxx> wrote:
>>
>>>Terry Pinnell wrote:
>>>
>>>> "Rod Speed" <rod_speed@xxxxxxxxx> wrote:
>>>>
>>>>>steve@xxxxxxxxxxxxxxxxxxxx wrote
>>>>>> Terry Pinnell <terrypinDELETE@xxxxxxxxxxxxxxxxxxx> wrote
>>>>>
>>>>>>> When just spinning, it's fine. But most of the time
>>>>>>> there's 'activity', and that makes a sort of deep
>>>>>>> 'throbbing' sound which gets rather wearing.
>>>>>
>>>>>> It could be a beat frequency between
>>>>>> the drive and a fan or another drive.
>>>>>
>>>>>Nope, you'd see that when just spinning.
>>>>>
>>>> No, Steve is right, I was mistaken/misleading in my initial
>>>> description. Now that I've been more careful and also taken the cover
>>>> off, I can clearly see/hear that the 'throbbing' is coming from the
>>>> fan mounted on top of the Athlon CPU heat sink.
>>>>
>>>> It's intermittent and it's not consistently the same sound. I can
>>>> alter it by touching the case.
>>>
>>>If you can alter it by touching the case it's either something loose or a
>>>panel resonance. If it's something loose find out what and tighten it.
>>>If it's a panel resonance there are at least three fixes--different case
>>>with different resonant frequency, alter the RPM of the fan so it's no
>>>longer in resonance with the case, or add some mass and damping to the
>>>resonant panel, which you can do by sticking in some purpose-made
>>>soundproofing (Dynamat Extreme <http://www.dynamat.com/> is the gold
>>>standard--"ice and water shield" that you can get in the roofing section
>>>building supply stores is cheap and works well but read all the fine
>>>print, if you go to <http://www.silentpcreview.com> you'll find
>>>discussion of other materials that work well).
>
> An immediate finding is that one of the 4 screws is not 'threading',
> IOW is completely loose and cannot be tightened up. However, all the
> others are firm (and I've just given them another 1/4 turn). The
> 'resonance' diagnosis is one possibility, which maybe I could cure
> with a replacement fan, or adding a couple of diodes in series with
> leads to reduce voltage applied? But how about bearing failure or dust
> build-up? As you saw from my photo, there's a fair amount of dust
> inside the fan. Could this unbalance it, and - combined with wear on
> the presumably cheap bearing - cause this throbbing? It changes every
> few minutes, sometimes deeper sometimes higher.

Blowing the dust out won't hurt, but an unbalanced fan wouldn't explain why
the sound goes away when you touch the case (I presume you mean by "case"
the metal box that forms the outer shell of the computer). As for the
bearing, if the fan is coming up to full RPM the bearing is not likely to
be causing a balance problem--if it's a sleeve bearing and it's failing it
would be slowing the fan down, if it's a ball it can make noise for a long
time before it stops functioning as a bearing. I wouldn't try oiling it
unless I was sure that it was the problem--with the machine shut down does
the fan spin freely with no feeling of roughness when you turn it by hand?
If so then the bearing is functional.

If it's sometimes louder and sometimes softer then there could also be a
beat-frequency component resulting from two devices at nearly the same RPM
going in and out of phase with each other.

>>Many thanks for that detailed reply, John. Will follow-up on all of
>>your suggestions and report back.
>

--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)
.

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