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Old Jan 25, 2013, 09:28 AM   #26
Fishrrman
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"noise came back on. i am taking it to genius bar as planned."

Dr. John's "Surefire Fix" to solve your problems…

Just buy a nice power strip or surge suppressor and plug the Mac and related peripherals into it (as I do).

When you shut down, just reach down and turn the power strip OFF.

When you want to reboot, reach down and turn the power strip ON.

Do this, and I _guarantee_ that you will NEVER be bothered by such problems again!
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Old Jan 27, 2013, 08:06 PM   #27
PavelT
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Quote:
Originally Posted by WilliamG View Post
If it's time-dependent, it may well be something
Hmm... I'd just wait till it does it again and note the time it happens during the day, to see if it's anything to do with that...
so it passed all of the apple diagnostics, but noise is very much there. i did notice that it does happen in the evenings everyday. regardless of what is plugged in...what could that mean?
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Old Jan 27, 2013, 08:14 PM   #28
hfg
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It could be "coil whine", magnetic vibration of a loose or poorly potted coil, transformer, etc. in the power supply which may be temperature sensitive (cooler in evening?). I'm sure that would pass their diagnostics as long as the voltages were within tolerance.

Or perhaps your hearing is better in the evening?

Did the Apple techs actually hear what you are hearing? I don't hear anything from mine, but my high frequency hearing isn't all that good anymore.

If you are still within the return period, that might be an option. Then just buy another one, although they may be hard to get right now.

======

I would imagine the power supply is still "on" even when off as it has to power the "wake on LAN", "wake on Bluetooth", monitor the power switch, etc.
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Old Jan 28, 2013, 09:08 PM   #29
PavelT
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Originally Posted by hfg View Post
It could be "coil whine", magnetic vibration of a loose or poorly potted coil, transformer, etc. in the power supply which may be temperature sensitive (cooler in evening?). I'm sure that would pass their diagnostics as long as the voltages were within tolerance.
it for sure buzzes after 5pm...i have been keeping track for about a week now. but i still dont understand what is happening...could it be a bad power cord? and would a line conditioner solve the problem, if my outlet was the culprit?
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Old Feb 10, 2013, 08:38 PM   #30
PavelT
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Quote:
Originally Posted by WilliamG View Post
If it's time-dependent, it may well be something to do with the power in your house. But obviously I can't prove it. That is very bizarre....

Hmm... I'd just wait till it does it again and note the time it happens during the day, to see if it's anything to do with that...
so i bought a APC voltage regulator, and plugged in my imac. and...the buzzing continues...

a recording of the electrical noise:
https://soundcloud.com/pavl-1/2012-i...ectrical-noise

Last edited by PavelT; Feb 10, 2013 at 08:49 PM.
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Old Feb 11, 2013, 03:15 PM   #31
drambuie
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Quote:
Originally Posted by PavelT View Post
so i bought a APC voltage regulator, and plugged in my imac. and...the buzzing continues...

a recording of the electrical noise:
https://soundcloud.com/pavl-1/2012-i...ectrical-noise

Wow, sounds just like a barking dog. Seriously, it's just the sound of the power inverter for the +5 volt standby power. If it bothers you, switch off the APC power switch. If you bought an APC UPS, I hope it's a full sinewave unit, such as the SmartUPS. The Back-UPS XS and RS units provide a stepped square wave on battery power, which could stress components in your iMac's power supply.
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