replaced mid 2011 imac 21.5" power supply
My computer was squealing faintly, like some car in the distance with a slipping belt. I notice it did it more when screen brightness was higher, or when the computer was doing anything processor intensive.
Repair was a piece of cake. I've opened this imac 5 times now i think, to put in a new ssd, clean out dust, etc. Taking the screen of is most of the work, and thats easy as long as you are careful. The new power supply from iFixit seems to have done the trick. computer is near silent again, especially when hd is spun down.
First, use tweezers to hold the lcd screws as you take them out, cuz the magnets want to grab them. Use the tweezers when putting them back too. Also get a good large microfiber cloth and carefully wipe down the lcd screen and inside of glass cover. it may take a few tries but you can get all the dust specs that will inevitably be there. Next, when first pulling the power supply out take your time and don't force it . Wiggle each corner in a one after the other sequence to work it out of the plastic frame. Finally, a spudger is very helpful with getting that large power connector undone.