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  • ch.denis Level 1 (0 points)
    I think it- Inverter Board
  • David Kaminsky2 Level 1 (5 points)
    Got a 24" imac last week and it has the screen dimming hum. It also does something else which may be related.

    When you adjust the brightness slider in display prefs it goes from bright to sort of bright. Every other Mac I've ever owned goes from bright to black. Has anyone else noticed this?

    I haven't tested this out yet but others ichatting with me also get an annoying hum from my computer during the ichat. Not sure if this goes away if I brighten the screen to the max.

    24" imac   Mac OS X (10.4.8)  
  • milkbone Level 1 (0 points)
    I am actually a little relieved to hear that others are experiencing this annoying hum when the brightness slider is moved to a lower level. I just received mine two days ago, and mine hums too. I'm finding it very difficult trying to get used to it.

    To anyone that has heard it, this is obviously not a fan or hard drive type of noise. It must be from the electronic device (inverter?) that controls the brightness of the backlighting tubes. I can reduce the intensity of the hum a tiny bit by squeezing the outside edges of the case in certain locations, so there must be some case resonance that's making it a little worse. But that's beside the point.

    I am going to try contacting Apple and see if there is a fix for this before I go transferring all my files and settings to this computer. I really hope there is a fix for it, as I see this annoyance as a very large drawback to anyone who works for long hours in a quiet environment (like me).

    iMac 24"   Mac OS X (10.4.8)  
  • Simon69 Level 1 (30 points)
    Just to add to the numbers -

    I have just received my 24" iMac, with 7600 card.
    I work in a silent environment and the hum is very audible when brightness turned down, though it is completely silent when turned up full.

    The internal fan and harddisk are almost silent by comparison.

    Still, it is much quieter than my old PC
  • milkbone Level 1 (0 points)
    I just returned from the Apple store at the Westfarms Mall in CT where I spoke with a tech at the Genius Bar. He said the humming was a "known issue" at Apple, and that their engineers are working on a fix. He had no insight as to what that fix might be, how Apple would implement it, or even if they could find a fix at all; but he said to keep checking Apple's support web site for information. If anyone hears anything else about this, please post it here so we will all know about it.

    24" iMac, 2.16 GHz   Mac OS X (10.4.8)   Screen is uneccessarily bright, and hums when dimmed.
  • jaumesignes Level 1 (0 points)
    well, i hope apple can fix the hum finally, because doesn´t do,it could be very anoying situation for them.
  • Level 6 (11,040 points)
    I am pretty sure they have a handle on this. I am sitting in front of an all-singing, all-dancing 24" iMac right now. It was manufactured about a month ago, so it is very recent. There is absolutely no hum evident no matter where the brightness level is set.

    So, if they have corrected the more recent iMacs to run silent, they must know what the problem is and how to correct it. Whether it can be done by a new firmware release or by a parts exchange program remains to be seen.

  • Simon69 Level 1 (30 points)
    I received my 24" iMac a few days ago, and it has the Hum sound when you turn the brightness down - it sounds a bit like the test tone on the TV at the end of programs (but lower in pitch.)

    I spoke to Apple Support and they agreed to swap it.

    So, some new ones do have the problem (I was told it was the inverter whatever that is.)

    Mine was a Custom Build (send from China) so perhaps they have some older stock ?? Dunno.
  • linkstate Level 1 (5 points)
    I just wanted to bump this topic back to the top as I am contemplating purchasing a 24" iMac after Macworld.

    Have any of you that contacted Apple about the hum received a solution of some kind?

    Has Apple 'officially' acknowleged this issue?

    Is this still an issue with recently shipped iMacs?

    Mac Mini 1.5 GHz PowerPC G4 1 GB DDR SDRAM   Mac OS X (10.4.8)  
  • milkbone Level 1 (0 points)
    I think the issue is still open. I called Apple support today (about a different issue) but asked about the hum problem too. The support person looked it up and said that Apple appears to be gathering information about it. She said that when someone calls in with a iMac noise issue, they are supposed to ask the customer a series of questions about it (when do you notice it, etc.). She knew nothing of a fix being iminent or anything else about the issue.

    On a side note, if you are considering purchasing a 24" iMac, you should be aware that there are reported problems regarding uneven screen brightness and color variation. You may want to review this thread and also search the forum for uneven display brightness issues. It all depends what you will use the iMac for and how much these issues will affect your satisfaction with it.
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