ASUS A7N8X-X: high frequency noise by an induction coil !

Archived from groups: alt.comp.hardware.homebuilt (More info?)

On Fri, 29 Oct 2004 17:49:30 GMT, "jimjim"
<netuser@blueyonder.co.uk> wrote:

>Hello,
>
> A high frequency noise is generated by an induction coil of the ASUS
>A7N8X-X. The noise occurs only when I am logged in WinXP (e.g. not when in
>FreeBSD), when accessing particular web pages (e.g. http://uk.asus.com/ is
>one of them, while http://www.asus.com/ is not !!), or when maximizing
>particular, already running, apps (MSN messenger is one of them). In some
>cases the noise persists even after closing down the web page or app.
>
> Moreover, a "clicking" noise of less applitude is also generated by the
>coil at all times, which is audible especially when I move the mouse.
>
>The paradox is that when the CPU is not idle but operates in loads of more
>than 3% the noises cease, and they are coming back again when the load is
>back to 0%.
>(I have monitored the voltage variation when the noise is or is not occuring
>and I have seen slight differences (e.g 0.1- 0.2 Volts). I am using a
>Qtechnology PSU, which is of a reletively good quality. I have also used for
>testing purposes a different one to exclude the possibility that it is a PSU
>related problem (it can be though)).
>
>I have also tried on another graphics card, and striped the computer down to
>only necessary components (e.g. just grapfics card and a hard disk). I also
>made sure that it is not a failed induction coil problem by returning the
>m/b back to the retailer and using a new one.All the latest drivers have
>been installed as well.
>
>Have you come accross what I have described above?Any solutions?


Yes but not on that particular board.
Basically a loose coil is operating at a resonant frequency
in the power regulation circuit. It's not necessarily
significant WHEN it does this, only that it does in everyday
use enough to be distracting. It's not the absolute
voltage that matters but rather the switching regulators' as
they're effected by the load to regulate.

There are a few things that can be done, depending on your
comfort level in doing them and ability, not to mention
whether the board is under warranty that you wish to
preserve. One of them might be disabling ACPI power
management so CPU is never at the lowest load that you
report causing this. Another might be replacing the
inductor or removing it, readjusting the coils and
reinstalling. Another might be taking some
semi-heat-resistant epoxy and covering the particular
inductor's coils (probably easiest thing for someone to do).

Which one is it?
http://69.36.189.159/usr_1034/a7n8x_inductor.jpg

Archived from groups: alt.comp.hardware.homebuilt (More info?)

On Sat, 30 Oct 2004 01:02:07 GMT, "jimjim"
<netuser@blueyonder.co.uk> wrote:

>>It's not the absolute voltage that matters but rather the switching
>>regulators' as
>> they're effected by the load to regulate.
>>
>Are you refering to the PSU's or the m/b's regulators.

Motherboard's, the 4 in the picture I linked.


>Is it possible that I will resolve the problem by replacing my PSU with
>another? (I am planning to check out my flatmate's one tomorrow possibly).

If it were a very very narrow range I might think it
possible, but generally no, only #3 on the picture should be
effected by the PSU.


>
>> There are a few things that can be done, depending on your
>> comfort level in doing them and ability, not to mention
>> whether the board is under warranty that you wish to
>> preserve.
>The mobo is under warranty indeed. Id rather return it back to the retailer,
>as its just 2 days since I recieved it, and buy a different make one. On the
>other hand, I have had such a good experience with ASUS that I am hesitant
>in going for a different brand (the question is which brand really :-)

Well I have an A7N8X-Dlx (where that pic came from) that
does not make any noise, also with a (mobile) Barton in it,
but another brand of board that does (did) make the noise
before I : Removed inductor, shifted coil, and applied
epoxy.

IIRC that board was a Shuttle MN31L, but there is potential
for any board to do it, there is nothing particularly unique
about your Asus board that makes it more susceptible.


>
>>One of them might be disabling ACPI power management so CPU is never at
>>the lowest load that you
>> report causing this.
>how can I do this?

Depends on OS, often it's necessary to reinstall the
operating system with the bios ACPI feature turned off.
Google will turn up tips on doing it, using "APM" instead.

>I guess this is why I dont hear the noise when i am running FreeBSD.

I'd have thought it supported ACPI too but I don't know. It
is definitely related to the power drawn by the CPU, or
rather the amperage based upon CPU utilization.

>
>>Another might be replacing the inductor or removing it, readjusting the
>>coils and
>> reinstalling.
>can i really remove it so to readjust the coils?

Well that's sort of a trick question. Yes you can, it's
just soldered in there and can be unsoldered... but no, if
you needed to ask or be told that then you probably don't
have enough circuit-board soldering experience that it'd be
good to try it, or at least not until after practicing on
some inductors on old/junk boards... You need a pretty hot
iron to get an inductor off since it's not only so much
metal but large areas of copper and solder. It's not really
hard to do, some would think it a lot easier than delicate
work but this being a brand-new motherboard you'll have to
make that call yourself... might be best to just return it,
or try the epoxy alone, liberally applied (epoxy that
hardens, not flexible type).


>
>>Another might be taking some semi-heat-resistant epoxy and covering the
>>particular
>> inductor's coils (probably easiest thing for someone to do).
>>
>whats this and do you really think that it will resolve the problem?

yes it should providing you can work the epoxy into the gaps
between the coils and torrite (doughnut) in the middle,
pretty well though perfection is not necessary.
Last time I did that I used "American Quick Set Epoxy
Steel", which is similar to "JBWeld" that you can find at
many retail stores, though I chose it primarily because it's
what I happened to have an arm's-reach away, there might be
something better but it did "good enough". Mainly you just
want a rigid epoxy that fixes the coils in place.

>(another issue is the one of the "clicking" noise generated when I move the
>mouse, as at least the high pitch noise due to me accessing web pages or
>maximizing running apps disappears when I push the coil with the back of my
>screw driver)

Not sure what that is, it might be your power supply or
audio (? if you're hearing it through the speakers).


>
>why is it that the noise is generated when I access particular web pages?any
>ideas?

It'd should be either a sound or a load due to processing
flash or animated images, scripts or (whatever the
particular page demands of the browser), OR just the
opposite as seem with your inductor, that the load is lower.


>
>
>> Which one is it?
>> http://69.36.189.159/usr_1034/a7n8x_inductor.jpg
>>
>the one on the left

Since the board is only 2 days old I'd send it back, if
replacement won't be too costly... Otherwise slap some epoxy
on it or take it to someone experienced with this type of
soldering who has a similar spare inductor lying around that
could be swapped in.

Archived from groups: alt.comp.hardware.homebuilt (More info?)

On Sat, 30 Oct 2004 01:40:02 GMT, kony <spam@spam.com> put finger to
keyboard and composed:

>>> Which one is it?
>>> http://69.36.189.159/usr_1034/a7n8x_inductor.jpg
>>>
>>the one on the left
>
>Since the board is only 2 days old I'd send it back, if
>replacement won't be too costly... Otherwise slap some epoxy
>on it or take it to someone experienced with this type of
>soldering who has a similar spare inductor lying around that
>could be swapped in.

I'd be wary of replacing just the one coil, if any at all. Inductors 1
and 2 should be as closely matched as possible because they come from
two identical load sharing circuits.


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.

Archived from groups: alt.comp.hardware.homebuilt (More info?)

P.S: my flatmate has the A7N8X-Dlx and met no probs. Dunno about the A7N8X-E
Dlx though

P.S: what about the Gigabyte GA-7N400-L mobo?

Archived from groups: alt.comp.hardware.homebuilt (More info?)

thx for the reply

kony, have you got the A7N8X-Dlx or the A7N8X-E Dlx?

>>P.S: what about the Gigabyte GA-7N400-L mobo?
>>
> I know of no problems with the Gigabyte board

is there any reliable and "independent" internet resource that presents
comparisons btw mobos?


>but wouldn't
> expect this particular issue with any board, it's random
> when it happens.
it has happened to me in two different A7N8X-X. So, I m wondering; am I so
unlucky that recieved two faulty m/b, or is it my setup and combination of
components that I am using !!

>The 7N400-L probably uses 12V for CPU
> power so you'd need a PSU with ATX12V connector (don't
> recall if your PSU has one or not)
hmm, i really dunno what you are saying here...Doesnt 7N400-L requires the
same PSU power plug as the A7N8X-X ?