Powerbook noisier on AC adapter

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Tom - 23 Jun 2005 20:28 GMT

My powerbook 1.5 aluminium makes quite a bit of noise from the
circuitry/memory/processor when set to Highest in processor performance
and running Classic. The noise is loud enough to be annoying. It's like
the electronic noise you get from memory but I think it comes from the
motherboard. I noticed that is stops when running off the battery only,
also if I put the ac adapter to my ear it makes the same noise. I wonder
if this is some kind of interaction between the switching psu and the
load the powerbook puts on it. I have tried different adapters and they
are all the same.

Has anyone run one of these powerbook off a external battery or other
true dc supply and noticed if the noise is still there? Also any ideas
what the minimum voltage the powerbook needs to run?

I would be prepared to find an alternative power source for the
powerbook, maybe an old fashioned one with a big transformer in it if it
would make a difference.

Thanks

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pailface88@yahoo.com - 24 Jun 2005 12:34 GMT

I have never heard of "the electronic noise you get from memory".

I do know that in some powerbook models the DC voltage inverter which
changes the low DC voltage to a high (several hundred volts AC) voltage
for powering the floresent LCD backlight can make a high pitched tone.
This tone can be altered by using the battery to power the computer or
the AC supply. The reason is that the battery and the AC supply produce
a different amount of voltage and therefore power available to the
inverter. Nothing to really be concerned about. It can likely be cured
by applying some epoxy to the inverter's transformer, which gets
physically loose over time.

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Tom - 24 Jun 2005 13:37 GMT

> I have never heard of "the electronic noise you get from memory".

It is difficult to hear but the last couple of powerbooks I have had
have done it. Have you never heard that clicking sound when scrolling
web pages with large images on them? you need to be in a fairly quiet
room with no fans on and a quiet HD etc.

I dont mind that sound, it the constant buzzing produced when running
classic with processor performance set to highest that annoys me.

> I do know that in some powerbook models the DC voltage inverter which
> changes the low DC voltage to a high (several hundred volts AC) voltage
[quoted text clipped - 5 lines]
> by applying some epoxy to the inverter's transformer, which gets
> physically loose over time.

It's not the inverter but I know the noise you mean, I have a flat
screen monitor that does that. the pitch changes as you adjust the
brightness of the display.

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Mac Forum / General / Portable Macs / June 2005

Powerbook noisier on AC adapter