Model A1312 / Mid 2011 / 2.7 & 3.1 GHz Core i5 or 3.4 GHz Core i7 Processor

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iMac has a buzzing noise on the top back left corner

I have a mid 2011 27inch Imac 3.4 GHz , i7 ,8GB. Recently there has been a buzzing noise that comes out the top back left corner. when i increase the brightness of the screen the buzzing noise becomes louder when I decrease the brightness the noise stays the same.

I have seen youtube videos of people recording the buzzing noise and some say it is a faulty power supply or the LED driver board.

Has anyone heard about this? and if so where could the noise be coming from?

Answered! View the answer I have this problem too

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I have this same problem. I also found that video on YouTube and yes, the sound increases as brightness does, as well as when scrolling a web page, etc. I work on a mac all day and for the price, I expect more...

I actually took it in to an Apple store for repair telling them it could be the Power Supply. The Genius guy heard the sound and said they'd have it back to me in 7 days. 9 days later I called and they told me they couldn't find anything wrong, thus no need for repair.

This doesn't sit well with me since it's a pain to lug around a 27" iMac.

So in the end, problem NOT fixed.

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You must have had a repair receipt with the description of the problem. I'd go back and up the chain to the manager, or contact apple support directly. They took the machine in, if there was nothing wrong why would they do that, and keep it 9 days? Something smells... don't let it go out of warranty like this.

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I have the same problem. Next time I will buy a pc and if something goes wrong I can just change the problematic part. But apple wants you to buy a new computer, of course. Bunch of thieves!

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I HAD the same problem. After some research I found the following solution that worked in my case.

Quote: "I did a lot of searching around but ended up finding the solution by accident. The problem, it turns out, didn't have anything to do with my screen. It was a fluorescent lamp plugged in to the same circuit as my computer. It was actually on the other side of the room but it creates interference in the AC power that conflicts with the power supply in the computer. Somewhat similar to what makes some car stereos buzz when driving."

Ergo: I changed all the fluorescent lamps in my room with LEDs >> buzzy noise fixed.

original solution see this link: https://discussions.apple.com/thread/343...

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This seems to be a "known issue" as they say in the Mac World. Could be the LED Backlight Board or the PSU. Since there's been quite a bit of chatter about this I would go to Apple Support and see if the machine in questoin is still under warranty, if not, there may have been a silent recall, extended warranty or coverage still in effect on your machine. If there doesn't seem to be, I would contact Apple directly and rais a bit of fuss- as there's quit a bit of this on the Discussion Board and other Mac Forums.

If this Answer is helpful please remember to return and mark it Accepted.

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I had the same buzzing noise issue with my mid-2011 27" iMac. Then one day I shut it down to move it and it was totally dead when I hit the power button. I replaced the PSU with a new one and the buzzing stopped – for about two weeks and then it started up again (with the new PSU unit in). It does the increase/decrease volume with brightness adjustment. I even tried lifting it off the desk to see if it was a vibration as some people had stated with no success. Seriously, this issue is all over the internet and there is no definitive answer/fix from Apple!

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After that I replaced power supply unit at Apple service center the noise totally gone. By the way, old Sata disk makes some noise though.

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My 27 inch 2011 iMac started to buzz like this after 5 years. It was silent for the first 5 years.

Then the buzz started. I changed the PSU. The buzz came back after 2 days. Then, I changed the LED backlight board and the buzz came back after an hour...

There is nothing left to change! WTF. If someone finds a fix, please let us know.

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I had the same problem and after 1 to 2 months of buzzing I turned it off and it would not start again! I am fairly certain that this is related to the PSU and I have already ordered one (I am based in Greece and I do all my work on my iMac so I can't afford to waste time with the fairly low quality Mac service available here).

This may or may not be relevant: I have been using the iMac with a 2nd monitor attached. The GPU has been getting pretty hot and I assume that this has placed a strain on the PSU.

Update: I decided to power the iMac with a UPS. For some bizarre reason the humming stopped immediately. It has been a month now with the UPS and the buzzing only happened once. I have ordered (and received) a new PSU from ifixit, which is sitting in my drawer for now.

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Hi Dimitris,

Can I ask you if using UPS on your iMac is still solving the buzzing problem? I'm also located in Athens and facing the same problem with my iMac. The whistling noise in the top back of my iMac is intermittently present when the iMac heats up. I'm considering applying your solution since I have to work on my Mac and cannot miss it for a week or more for diagnostics at Apple service. I read somewhere that this problem happens only with 220V and not 110V power supply.

Thanks for you answer!

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Yesterday I bought UPS(Eaton ENV-600H) including AVR(Automatic Voltage Regulator) for my iMac 27" 2009 mid.

After that installed, buzzing or humming did NOT stop immediately, but I can feel it has now different noise.. more moderate one.

I just want to tell you that dimitrisdovinos's lucky case may not for all.

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Hi Jin Hwa Kim,

Thanks for your update. From my last post the noise stopped spontaneously. I cannot explain it, but time ago I found a post in a blog describing the same phenomena. The post was describing how after cca two months buzzing stops by itself. And indeed for me it stopped +- in the same period. I just hope it is a permanent change. I wish the same happened to your machine. Kind regards, iGor

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Hi guys

update on my side. I had the same problem and I was going crazy about it... I had replaced the PSU to solve a problem related to the iMac not starting... I thought it was the PSU (it would actually "try" to start for a few secs and then would power down... and loop again) - the problem was actually a faulty memory!

the noise was driving me crazy (due to the pitch and because I was used to a silent iMac...) and I thought it was the fans... e.g. that something related to the brushing...

When I saw this post I decided to put back the *Original* PSU... and miracle... the noise went away

It was definitely an electrical noise and definitely coming from the PSU area --- so replacing the PSU (with the original one...) solved it

luis

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Hi, I'm back.

UPS doesn't make better even after few weeks. So I backed up all data and took it to the Apple service center. Apple guy said he had doubt on Hard-disk fan, but I insisted that it must be PSU coil something problem.

After few days he called me and he said PSU is the root of weird noise, Replacement will cost about $140 due to the expired warranty. But, luckily, LCD panel will be replaced for FREE because of its own defect (He found the notorious stain mark on the display I couldn't even notice). New LCD panel is worth $900.

Now my iMac is dead silence. The most loud noise is the little static sound when sometimes reading hard disk. And my $80 UPS (perhaps its AVR functionality?) may prevent another PSU noise I guess, I hope.

p.s. iMac 27" is very heavy. Two men or using car. Awful.

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