Imac 27 BUZZING

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My mid-2011 27" iMac started making an annoying buzzing sound, like an arcing/crackling, coming from the upper left corner of the screen. The noise got louder with screen brightness and when scrolling, and could even be heard faintly while the iMac was in sleep mode. I tolerated this for months until it was just driving me crazy. After reading various blogs (including Apple support communities) I determined it was most likely the power supply module. I bought a new supply module (for my particular model) and the suction cups used to remove the front face of the iMac screen from iFixIt, and they arrived in just a couple of days.

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The repair went exactly as expected, thanks to the step-by-step instructions provided on this site. I used the iPad instructions to follow along step by step as I progressed through the repair. From start to finish it was less than one hour. No more buzzing.

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The heavy duty suction cups, used to remove the front face of the screen, left marks after removal. With some scrubbing, the marks can be removed, but in hindsight, cleaning the screen and suction cups BEFORE applying them probably would have eliminated this problem.