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Powerbook noisier on AC adapter

Message #1 - Posted 2005/06/23 - Tom

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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apax63 'at' dsl 'dot' pipex 'dot' com

Message #2 - Posted 2005/06/24 - pailface88

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.

Message #3 - Posted 2005/06/24 - Tom

pailface88@yahoo.com wrote:

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 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.

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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apax63 'at' dsl 'dot' pipex 'dot' com

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