Laptop makes barely aubible high pitched whine .. when powered down

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Hi all,
This is a follow up to my earlier post about 'Sony Vaio .. fails to boot" ..
perhaps I should have replied to my thread but, some of you experts out
there might have ignored my less interesting subject which had been replied
to already.

So as the subject line of this thread says, this laptop, which fails to boot
makes a barely audible high pitched whine when it is powered down, as long
as it has the battery inserted or the power cable connected or both.

I can only hear the whine when I place my ear against the laptop. The whine
changes slightly when I connect or remove the power cable or battery.

As you would expect there is no whine when there is no battery or power
cable connected.

So  what is this whine? Might there be a short circuit in this laptop? has
some component failed to create this noise?

any ideas will be greatly appreciated.

Re: Laptop makes barely aubible high pitched whine .. when powered down

On 8/16/2010 4:09 PM, 123Jim wrote:
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Typically, such a noise would be associated with a switching regulator or
power converter. This is possibly part of the battery charger which would
correspond with the conditions you describe. Most often the noisemaker
would be an inductor vibrating a bit at the rate at which the circuit
switches or, I believe, at some subharmonic of that frequency. A laptop has
a switching regulator/converter circuit which converts the battery voltage
to the various voltages which the computer requires. One other possibility
occurs to me at the last moment before posting and that would be the
circuit which generates the high voltage required by the fluorescent
backlight behind the LCD but that seems _far_ less likely than the
regulator/converter/charger theory.

Re: Laptop makes barely aubible high pitched whine .. when powered down

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Thanks for responding,
It grieves me horribly but I think I have to admit defeat with this laptop
.. I just don't have the time or the spare parts needed to work through the
possibilities. It might be, as I think you allude to, a problem on the
charger board, but why would there be any current at all when the power
cable is not attached, or when the battery has been removed? .. In both
those cases no current is required, but as I say the noise persists in both
those cases ..

Re: Laptop makes barely aubible high pitched whine .. when powered down

On 8/16/2010 7:55 PM, 123Jim wrote:
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I may have totally misread the original post then. Apologies if I did. As
you note (assuming I'm now reading correctly) the noise is there when the
battery + the cord are there, or when the battery is there with no cord, or
when the cord is there with no battery. In all three cases where the noise
is present there is a source of power -- it only goes away when there is no
source of power. That still leads me toward regulator/converter/charger
circuitry with a _very_ slight edge given to the charger side. And yes, it
could be a short circuit. Or an open circuit. Or something else entirely.

As you obviously know, troubleshooting laptops is a serious PITA if you
don't have the proper resources. As with many computer problems, having all
of the proper known-good parts to swap in and out is often the key. With
desktops almost anything is swappable but with notebooks there is too much
specialization to make that possible unless you are very lucky. Add to that
the fragility of some parts and you have a serious mess. I have an elderly
P4 notebooks which was damaged in the trunk of my car on a trip despite
being in a good case. It now works perfectly -- as long as it is opened at
precisely 90-degrees and then turned upside down to resemble an old-style
tent. Not the best typing or viewing position. I beat myself up trying to
fix it and am pretty sure that one or more hair-thin traces on the
motherboard have cracked but the motherboard is unobtainable AFAIK and it
was easier and cheaper (time is money even for a retiree) to buy a new
computer and promise myself to be more careful when I pack it in the car.
Sometimes a strategic retreat is called for.

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