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27" iMac whines when brightness turned down

peteullo

peteullo

macrumors regular
Original poster
Dec 13, 2009
245
57
Scranton, PA
I have a 27" iMac w/ i7 that has been driving me nuts lately.. When you turn down the brightness on the screen the unit begins to let off a high pitch whining noise. On full brightness it makes no noise at all but soon as a I lower the brightness one click the whining starts. I also noticed that when I turn down the brightness all the way to 0 that the noise completely stops.

I have another (3)27" iMac's w/ i5 that don't seem to have these problems. I was wondering if this has happened to anyone else?

I placed a call into a local authorized service center so I have already begun the process of hopefully getting this repaired.
 
peteullo said:
I have a 27" iMac w/ i7 that has been driving me nuts lately.. When you turn down the brightness on the screen the unit begins to let off a high pitch whining noise. On full brightness it makes no noise at all but soon as a I lower the brightness one click the whining starts. I also noticed that when I turn down the brightness all the way to 0 that the noise completely stops.

I have another (3)27" iMac's w/ i5 that don't seem to have these problems. I was wondering if this has happened to anyone else?

I placed a call into a local authorized service center so I have already begun the process of hopefully getting this repaired.
Click to expand...
I have been through 5 replacements with different issue, and all 5 have the high pitch and buzzing issue, when increasing or decreasing the brightness. I don't think there is a solution for that yet, just like the yellow tinge.
 
swee5420 said:
I have been through 5 replacements with different issue, and all 5 have the high pitch and buzzing issue, when increasing or decreasing the brightness. I don't think there is a solution for that yet, just like the yellow tinge.
Click to expand...

Like I was saying.. I have 3 other iMacs around the house without that issue but for some reason mine is sooo bad that I can hear it from across the room as soon as it kicks on.

I dropped off the computer at an Apple Store rather than the authorized center. I was told they ordered a Backlight board and I think a new screen as well. I also mentioned to them from what I read on Apples forums that a few people reported power supplies fixing their problem and they added that to the parts request list.

I should have the computer back in a few days so I will update then.
 
peteullo said:
Like I was saying.. I have 3 other iMacs around the house without that issue but for some reason mine is sooo bad that I can hear it from across the room as soon as it kicks on.

I dropped off the computer at an Apple Store rather than the authorized center. I was told they ordered a Backlight board and I think a new screen as well. I also mentioned to them from what I read on Apples forums that a few people reported power supplies fixing their problem and they added that to the parts request list.

I should have the computer back in a few days so I will update then.
Click to expand...

Please remember to report to this thread if the issue is fixed
 
Sounds like inverter whine to me. The replaced backlight board should fix it, hopefully.
 
My i7 does not have this issue. However, all of my Apple 23" Cinema Displays did. At max brightness, there was no sound from the screen, but at anything less than full brightness, there was a sound emitting from the screen that would drive me nuts.
 
I am on my third 27" iMac due to screen brightness noise issues. The issue normally occurs when the computer is running hotter (ex. ripping a dvd in Handbrake which uses all 4 cores). At most points <50% brightness, it is pretty much silent, but anything above 50% brightness, I begin to hear high pitched, almost dog-whistle noises combined with a buzzing noise that almost sounds as if there is a fly trapped in the upper left corner. I have taken audio samples and they've been forwarded to the engineering department through a senior adviser on the previous 2 iMacs. The first one that I received back in December had the exact opposite issue... at <50% brightness, it would make the fly buzzing sound along with the high pitched whistle noise. The last two have been at brightness above 50%. Apple Care was suspecting an environmental issue that was causing the noises... something like dirty electricity, causing the noises. I am just worried about long-term hardware issues due to misappropriated electricity.

If anyone gets any answers on this, please post back here. I'll try to do the same once Apple Care gets back with me. At this point, I am considering opting for a refund and holding out until the next refresh comes. I'm just not sure that a 4th replacement is going to solve the problem.
 
same issue here.

I have the same issue with my Imac, though This was never a problem, When i got my imac (4th one after replacements) everything was fine. I am not sure if the last firmware update did not bring this issue out. Looks like I will be dragging the damn thing into the apple store soon, wish it was not so heavy.
 
Now that I receive an imac with almost no yelow tinge, I have this problem also, it seems like a high-pitched noise coming from the left corner.
I can´t believe that they solve one problem and then create other.
 
Just got the iMac back on Tuesday. Apple replaced the LED Backlight board and problems seems to be cured. I hope this helps anyone who may have these issues.
 
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