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?
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.
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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.