Previous 1 2 Next 25 Replies Latest reply: Nov 21, 2010 3:29 AM by Paulmeijer
coxorange Level 1 Level 1 (40 points)
Just restored everything from my Time Machine backup and wanted to start working
with my new iMac 27" i3 3.2GHz but there is this annoying humming noise!

It's not from the HD - I hear the HD only during reading/writing and this is quite normal.

The humming noise sounds like it's from the power transformer
and I can also feel a vibration when I lay my hand on the iMac.

Anyone else has this issue?

I hope this is not NORMAL with the new iMac!!

I've had 3 other Macs before (see below) and NEVER heard ANY noise.
As far as I'm informed, the previous 27" iMac generation didn't have
this humming noise either.

Please answer ASAP - I have much work to do. Thanks!

iMac 24" 2.8GHz; 2x iMacs 21.5" 3.06 GHz, Mac OS X (10.6.4), Kensington Expert Trackballs
  • rkaufmann87 Level 8 Level 8 (46,465 points)
    It should be dead quiet. Contact AppleCare immediately, the phone number is in your owners manual.

    Regards,

    Roger
  • babowa Level 7 Level 7 (26,080 points)
    I agree with Roger - I bought the very same machine on Tuesday and I can't hear it at all.
  • coxorange Level 1 Level 1 (40 points)
    Thanks for the replies - I thought this can't be normal!
  • Jogon Level 1 Level 1 (0 points)
    How loud is the hum? I have one just the same save mine is an i5 2.2 quad and I have a hum..in fact as I type the rest of the house is asleep but my imac is low level humming
  • Scott Billings Level 4 Level 4 (1,655 points)
    It kind of depends on where the noise is coming from. If it's anywhere in the top left quadrant of the screen, definitely take it back or get it fixed. It's probably not dangerous to leave for a day or two, but I wouldn't really chance it. If the display itself seems to be making noise... That's annoying but not really anything you need to worry about immediately.

    But during normal operations, like not playing games or anything stressful such as that, the iMac should be pretty much silent.
  • coxorange Level 1 Level 1 (40 points)
    I can hear it up to a distance of 1.5 m.
    When sitting directly in front of the iMac
    (working position) it's really a pain!
  • coxorange Level 1 Level 1 (40 points)
    It kind of depends on where the noise is coming from. If it's anywhere
    in the top left quadrant of the screen, definitely take it back or get it fixed.


    OK I tried to locate the source of the humming noise:
    It's coming from the left side, but not sure if from the top or bottom. Maybe the top...
    I'm quite certain it's not coming from the top right quadrant.

    It's probably not dangerous to leave for a day or two, but I wouldn't really chance it.


    I can't return the iMac before Monday. So if it IS dangerous, what could happen...!?

    If the display itself seems to be making noise... That's annoying
    but not really anything you need to worry about immediately.


    I don't think the display could cause such a low frequency noise.
    Sounds like a transformer or motor.

    But during normal operations, like not playing games or
    anything stressful such as that, the iMac should be pretty much silent.


    It does absolutely nothing.
  • Macmateo Level 1 Level 1 (0 points)
    I got my 27" 2.88 i5 yesterday, and does definitly not hum. There is a soft tapping noise which seems to come from the hard disk , but apart from that it's very quiet. To hear the fans you have to put your ear right over the ventilation slot at the top rear - careful not to burn your ear though - but thats another discussion
  • coxorange Level 1 Level 1 (40 points)
    There is a soft tapping noise which seems to come from the hard disk,
    but apart from that it's very quiet. To hear the fans you have to put your ear
    right over the ventilation slot...


    ... just like my other iMacs behave.
  • Paul_31 Level 6 Level 6 (13,105 points)
    When I first got my new iMac last October my wife could hear a persistent humming noise that she reckoned was really loud - I couldn't hear a thing, although I've got good hearing. Must be something do do with us hearing different frequencies. Anyway, after a couple of days she turned around and declared that the irritating humming sound had stopped.
    Maybe it'll cure itself in a day or so, if not a phone call to Apple I guess.
  • Scott Billings Level 4 Level 4 (1,655 points)
    There are two power supplies in the iMac starting with the Late 2009 models. One is the main power supply, the other steps up the voltage for the LED backlighting. The main PSU is a bit left of center on the top of the system, the other one runs along the left edge from pretty close to the top to about the middle of the system. One of those is likely defective.

    While I'd put the odds as pretty low, the worst case scenario would be one of those catching fire and completely destroying the computer.

    I'm no electrical engineer, so if there are any out there who want to disagree with what I'm about to say, I'd definitely defer to them. But I'd say the humming is probably a sign that the PSU is not having it's power flow regulated properly and somewhere there's a buildup/backup of energy. It could also be a lack of proper shielding that's creating a kind of sympathetic resonance. Lots of possibilities, but so long as the frequency/pitch of the sound is remaining constant... PROBABLY nothing to worry about in the next 2-3 days.

    Again, I'll defer to any electrical engineers in the audience, but having worked as a hardware tech for around 2 years, I've run across people who have had loud PSUs for years with no obvious ill effects. I wouldn't recommend it myself, but there's at least anecdotal evidence to suggest it's more of an annoyance than anything.
  • coxorange Level 1 Level 1 (40 points)
    Thanks a lot for the detailed information! I will take care.

    In the meantime I contacted Apple. I reported the problem and was asked
    to disconnect everything and to RESET the iMac.
    Unfortunately it was not better after the procedure, hence I was told to
    contact my dealer (comet.co.uk) to arrange a collection & exchange.
    I hope the next one will be quiet...

    BTW Could such a fault result from ungentle transport by the courier?
  • Scott Billings Level 4 Level 4 (1,655 points)
    There's a small chance, but I'd say it's highly unlikely. The PSU's are all solid state components, so being tossed around a bit shouldn't really hurt them.

    And what they had you do was a SMC reset. I would be quite surprised if that had solved the issue, but I suppose it was worth a try given it only takes a few seconds.

    Yours is a pretty classic case of a manufacturing defect. It happens. I would recommend that before you return the system you first make sure you have a backup of any files you may have created in the short time of owning it. Then boot off the install DVD and load up Disk Utility. From there, I'd recommend doing a drive erase, and at a minimum selecting to zero out the drive. That should make it pretty hard for someone to recover any data should they decide to get nosy and start snooping around. Maybe do this the night before the system is set to be collected. Even selecting the 7-pass option. It will not likely finish overnight, but it will have made probably 2-3 passes in that time and you can just stop after that and reinstall the OS, which will further obliterate a lot of data.
  • coxorange Level 1 Level 1 (40 points)
    Thanks again for this valuable information!
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