Introduction
The iMac uses an incredibly hard to get to power supply. It has 24-Pins. This will require taking the iMac fully apart.
Tools
Parts
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Start by flipping the iMac upside-down. It may help to lay it on a towel, so you don't damage the screen, or scratch the face.
 
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Remove this Phillips screw.
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Using a flathead screwdriver, work your way around the bottom cover, until it comes off.
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Then, lift the bottom cover up and out, and set it aside.
 
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Now, remove the DB-15 Video connector from the logic board.
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It may be helpful to use a Phillips screwdriver to remove the thumbscrews.
 
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Remove the front panel connector. (You may also need to remove an additional screw that connects the front panel connector to the logic board assembly).
 
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Now, remove these Phillips screws.
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Now, grab the logic board assembly by the piece of plastic, and lift it out.
 
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The logic board assembly. This is the heart of the computer, it contains the motherboard, CPU, RAM, V-RAM, PRAM battery, the hard drive, and the optical drive.
 
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Removing the front bezel:
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There isn't a great position to put the iMac in to remove the front bezel. I recommend flipping it so it it like it would normally be positioned.
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Remove these two Phillips screws.
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Now, work your way around the bezel with a flathead screwdriver, and then, pivot it up towards the top, and remove it.
 
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Removing the translucent plastic:
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Removal of the front bezel will reveal two screw covers on the top, pop them off with a Phillips screwdriver.
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Now, use a Phillips screwdriver to remove the screws.
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You can now remove the plastic.
 
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Power Supply:
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Removal of the EMI shield will reveal two major circuit boards.
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The Display Driver:
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The Power Supply:
 
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Now, swing the board out, and remove the following connectors:
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AC Power
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To System Fan
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Don't remove this. It comes free with the logic board power.
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To Display Driver
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The connector that is attatched to the logic board; to remove it, simply thread it through the hole in the metal:
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Now, you should be able to remove the power supply.
 
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To reassemble your device, follow these instructions in reverse order.
One comment
i have exactly this problem with my vintage imac g3 took it to repair shop they said could not find it do you know where i can get this power supply and pay to have it installed