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From: Merciadri Luca on 16 May 2010 05:50
Hi,

I am using a Philips HQ 8000 100-240V /D 50-60 Hz, 9W, shaver charger
and transformer. I always let it plugged in, and then, to charge the
shaver, I plug the shaver in the charger, and everything's right.

However, it makes a very irritating noise, some piercing one, even if
the shaver is not plugged. This sound is so much unbearable that I
have to disconnect it before going to bed. I know that, practically,
it is disadviced to let a transform connected to the network without
any output, but why is it making so much noise? I have dozens of other
transformers which never make such a noise.

Thanks.
From: Jasen Betts on 16 May 2010 06:33
On 2010-05-16, Merciadri Luca <merciadriluca(a)gmail.com> wrote:
> Hi,
>
> I am using a Philips HQ 8000 100-240V /D 50-60 Hz, 9W, shaver charger
> and transformer. I always let it plugged in, and then, to charge the
> shaver, I plug the shaver in the charger, and everything's right.
>
> However, it makes a very irritating noise, some piercing one, even if
> the shaver is not plugged. This sound is so much unbearable that I
> have to disconnect it before going to bed. I know that, practically,
> it is disadviced to let a transform connected to the network without
> any output, but why is it making so much noise? I have dozens of other
> transformers which never make such a noise.


http://en.wikipedia.org/wiki/Switched-mode_power_supply

serch for the text "acoustic noise" read the rightmost column

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From: Merciadri Luca on 16 May 2010 08:57
On May 16, 12:33 pm, Jasen Betts <ja...(a)xnet.co.nz> wrote:
> On 2010-05-16, Merciadri Luca <merciadril...(a)gmail.com> wrote:
>
> > Hi,
>
> > I am using a Philips HQ 8000 100-240V /D 50-60 Hz, 9W, shaver charger
> > and transformer. I always let it plugged in, and then, to charge the
> > shaver, I plug the shaver in the charger, and everything's right.
>
> > However, it makes a very irritating noise, some piercing one, even if
> > the shaver is not plugged. This sound is so much unbearable that I
> > have to disconnect it before going to bed. I know that, practically,
> > it is disadviced to let a transform connected to the network without
> > any output, but why is it making so much noise? I have dozens of other
> > transformers which never make such a noise.
>
> http://en.wikipedia.org/wiki/Switched-mode_power_supply
>
> serch for the text "acoustic noise"  read the rightmost column
Thanks. And so, I have nothing to do, do I? This is the only one which
I get such a problem with.
From: Jamie on 16 May 2010 10:45
Merciadri Luca wrote:

> Hi,
>
> I am using a Philips HQ 8000 100-240V /D 50-60 Hz, 9W, shaver charger
> and transformer. I always let it plugged in, and then, to charge the
> shaver, I plug the shaver in the charger, and everything's right.
>
> However, it makes a very irritating noise, some piercing one, even if
> the shaver is not plugged. This sound is so much unbearable that I
> have to disconnect it before going to bed. I know that, practically,
> it is disadviced to let a transform connected to the network without
> any output, but why is it making so much noise? I have dozens of other
> transformers which never make such a noise.
>
> Thanks.
It's possible that it hasn't enough load on it and is cycling on/off.
Some chargers are designed to do this if it does not detect a proper
load due to the possibility of a bad battery or doing battery detection
cycles.

And some, like I said, are just plain noisy with no load on them
because they are designed for the battery load which is much greater
than just sitting idle. Normally, there is a load in there to help this
out how ever, its been a big thing about wall adapters sucking power
while your device isn't plugged in. Vampire Wallworts is a slang name
for that. So the noise you hear could also be the detection circuit
operating and looking for a load to switch and it could be on the edge
of a trigger.


From: Merciadri Luca on 16 May 2010 11:58
On May 16, 4:45 pm, Jamie
<jamie_ka1lpa_not_valid_after_ka1l...(a)charter.net> wrote:
>   It's possible that it hasn't enough load on it and is cycling on/off.
>    Some chargers are designed to do this if it does not detect a proper
> load due to the possibility of a bad battery or doing battery detection
> cycles.
>
>    And some, like I said, are  just plain noisy with no load on them
> because they are designed for the battery load which is much greater
> than just sitting idle. Normally, there is a load in there to help this
> out how ever, its been a big thing about wall adapters sucking power
> while your device isn't plugged in. Vampire Wallworts is a slang name
> for that. So the noise you hear could also be the detection circuit
> operating and looking for a load to switch and it could be on the edge
> of a trigger.
Okay, I just plugged the shaver in, and put my ear next to the
transformer, and, actually, the noise is really even more perceptible
when the saver is plugged. This doubles the noise.
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