iMac Intel 21.5" EMC 2638 Power Supply Replacement

Sam Goldheart and 4 other contributors

Last updated on March 25, 2024

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Introduction

Go to step 1

Use this guide to replace the power supply.

What you need

Parts

Tools

Step 1 Display Assembly

iMac Intel 21.5" EMC 2638 Power Supply Replacement, Display Assembly: step 1, image 1 of 1

Tool used on this step:

iMac Intel 21.5" Cardboard Service Wedge

$4.99

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With the hinge free to move, the iMac will be unbalanced and hard to work on. Repairs are fast and easy with an iMac service wedge, but can be completed without one.
If you are using the iFixit cardboard service wedge, follow these assembly directions to put it together.
Before beginning any work on your iMac: Unplug the computer and press and hold the power button for ten seconds to discharge the power supply's capacitors.
Be very careful not to touch the capacitor leads or any exposed solder joints on the back of the power supply. Only handle the board by the edges.

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Step 2

Starting on the left of the display, near the power button, insert the iMac Opening Tool into the gap between the glass panel and the rear enclosure.
The hub on the iMac Opening Tool will keep you from pushing the wheel in too far. If using a different tool, insert no more than 3/8" into the display. Otherwise, you risk severing antenna cables and causing serious damage.

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Step 3

iMac Intel 21.5" EMC 2638 Power Supply Replacement: step 3, image 3 of 3

Use the tool like a pizza cutter—roll it along through the gap, and it will cut the foam adhesive through the center.
Be sure to always push with the handle behind the cutting wheel. If you pull, the wheel might get pulled out of the handle.
Run the tool up along the left side of the display.

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Step 4

iMac Intel 21.5" EMC 2638 Power Supply Replacement: step 4, image 3 of 3

Continue running the tool up around the top left corner.

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Step 5

Cut the adhesive along the top left of the display.

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Step 6

Continue along the top of the display.
You may want to run the tool back and forth through what you've already cut a few times, to ensure you get as much of the adhesive separated as possible.

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Step 7

iMac Intel 21.5" EMC 2638 Power Supply Replacement: step 7, image 3 of 3

Push the tool around the top right corner of the display.

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Step 8

Wheel the tool down along the right side of the display.

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Step 9

Finish pushing the opening tool to the bottom of the right side of the display.
At this point, you'll want to run the tool back around the entire display, to ensure you cut as much adhesive as possible.

Edit

Step 10

iMac Intel 21.5" EMC 2638 Power Supply Replacement: step 10, image 3 of 3

Tool used on this step:

Plastic Cards

$2.99

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While the opening tool cut most of the adhesive, the display will still be slightly adhered to the case. A plastic card will be necessary to free up the last of this adhesive.
Set the iMac face-up on a table.
Starting from the top right corner of the iMac, wedge a plastic card between the display and frame.
Be careful not to insert the plastic card more than 3/8", or you may damage internal components.

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Step 11

Gently twist the plastic card sideways to create a gap between the display and frame.
Move slowly and be careful not to stress the display glass too much—you only need to make a gap of about 1/4".

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Step 12

iMac Intel 21.5" EMC 2638 Power Supply Replacement: step 12, image 3 of 3

Slide the card toward the center of the display to cut any of the remaining adhesive along the top right corner of the iMac.
Be sure to stop before the iSight camera, or you may damage it.

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Step 13

Wedge the plastic card into the top right corner once again, and leave it there to prevent the adhesive from resticking.

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Step 14

iMac Intel 21.5" EMC 2638 Power Supply Replacement: step 14, image 3 of 3

Insert a second plastic card into the gap between the display and frame near the top left corner of the iMac.

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Step 15

Gently twist the card upward, slightly increasing the space between the display and frame.
As with the other side, twist slowly to allow the adhesive time to separate, and be careful not to over-stress the display glass.

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Step 16

iMac Intel 21.5" EMC 2638 Power Supply Replacement: step 16, image 3 of 3

Slide the plastic card toward the center, again stopping just before the iSight camera.

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Step 17

Wedge the plastic card back into the top left corner.

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Step 18

iMac Intel 21.5" EMC 2638 Power Supply Replacement: step 18, image 3 of 3

With both plastic cards inserted as shown near the corners, gently twist the cards sideways to increase the gap between display and case.
If there are any sections that seem to stick and won't separate, stop twisting and use one of the cards to cut the remaining adhesive.
Begin to lift the top of the display up from the frame.
Only lift the display a few inches—the display data and power cables are still connected to the logic board.

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Step 19 Display

iMac Intel 21.5" EMC 2638 Power Supply Replacement, Display: step 19, image 1 of 2

iMac Intel 21.5" EMC 2638 Power Supply Replacement, Display: step 19, image 2 of 2

While holding the display up with one hand, use the other hand to unplug the display power cable.
Lift the display up enough to have easy access to the connector, but not so much that you stretch the cables and stress their connections (about 8").

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Step 20

iMac Intel 21.5" EMC 2638 Power Supply Replacement: step 20, image 3 of 3

Use the tip of a spudger to flip up the metal retaining bracket on the display data cable.
Carefully pull the display data cable from its socket on the logic board.
Be sure to pull the display data cable connector straight out of its socket.

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Step 21

Lift the display up to a near-vertical position.
At this point there is still a strip of adhesive along the bottom of the display, that will hold the display to the frame like a hinge. You can loosen this adhesive by working the display up and down a few times.

Edit

Step 22

iMac Intel 21.5" EMC 2638 Power Supply Replacement: step 22, image 3 of 3

Tool used on this step:

Plastic Cards

$2.99

Add To Cart

Be very careful not to touch the capacitor leads or any exposed solder joints on the back of the power supply (boxed in red).
Grasp the small tab at the end of one of the bottom edge display adhesive strips and pull the adhesive toward the top of the iMac to remove it.
Repeat this step with the other adhesive strip and remove it.
If either adhesive strip breaks before it's removed, use a plastic card to slice through the remaining adhesive.

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Step 23

iMac Intel 21.5" EMC 2638 Power Supply Replacement: step 23, image 3 of 3

Lift the display up from the frame and remove it from the iMac.
It may be necessary to slowly lift from one side, to peel against the remaining adhesive.
Be very careful handling the display—it's big, heavy, and made of glass.
During reassembly, head over to our display adhesive guide to install the new adhesive.

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Step 24 Lower Support Bracket

iMac Intel 21.5" EMC 2638 Power Supply Replacement, Lower Support Bracket: step 24, image 1 of 2

iMac Intel 21.5" EMC 2638 Power Supply Replacement, Lower Support Bracket: step 24, image 2 of 2

Remove the following five Phillips screws holding the lower support bracket in place:
Four 3.2 mm screws
One 1.7 mm screw
On at least some EMC 2544 machines, all five screws are the same size.
You may need to peel up the display adhesive lining the bottom edge of the iMac enclosure to access the screws.

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Step 25

Remove the lower support bracket from the iMac enclosure.

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Step 26 Hard Drive Brackets

iMac Intel 21.5" EMC 2638 Power Supply Replacement, Hard Drive Brackets: step 26, image 1 of 1

Remove the following screws securing the hard drive bracket to the rear enclosure:
Two 21 mm T10 Torx screws from the left-hand hard drive bracket.
One 9 mm T10 Torx screw.
One 27 mm T10 Torx screw.

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Step 27

Remove the left and right hard drive brackets from the iMac.

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Step 28 Power Supply

iMac Intel 21.5" EMC 2638 Power Supply Replacement, Power Supply: step 28, image 1 of 3

iMac Intel 21.5" EMC 2638 Power Supply Replacement, Power Supply: step 28, image 2 of 3

iMac Intel 21.5" EMC 2638 Power Supply Replacement, Power Supply: step 28, image 3 of 3

The next few steps bring your hands close to the exposed face of the power supply. Do not touch the face of the power supply or any of the exposed solder. Touching it risks a high voltage shock from the many large capacitors attached to the board.
Use the tip of a spudger to push each side of the power button cable connector and gently walk it out of its socket.

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Step 29

Use the tip of a spudger to push each side of the power supply control cable connector and gently walk it out of its socket.

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Step 30

Remove the two 7.2 mm T10 Torx screws securing the power supply to the rear enclosure.
In newer model iMacs these are 7.2 mm T8 Torx screws.
During reassembly, be careful not to trap the power button wire behind the board.

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Step 31

When working on the power supply, be very careful not to touch the capacitor leads or any exposed solder joints on the back of the power supply. Only handle the board by the edges.
Tilt the power supply forward.

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Step 32

iMac Intel 21.5" EMC 2638 Power Supply Replacement: step 32, image 3 of 3

Pull the power supply slightly up and out from the rear enclosure.
Rotate the power supply counterclockwise, lifting the right side up about an inch higher than the left.

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Step 33

Slide the power supply to the right to clear the screw posts on the rear enclosure.

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Step 34

iMac Intel 21.5" EMC 2638 Power Supply Replacement: step 34, image 3 of 3

Rock the power supply forward and remove it from its recess in the rear enclosure.
Do not try to completely remove the power supply from the iMac yet—it is still connected to the logic board.

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Step 35

Be very careful not to touch the capacitor leads or any exposed solder joints on the back of the power supply. Only handle the board by the edges.
Flip the power supply over to access the DC power cable connection behind the logic board.
Squeeze the tab on the back side of the DC power cable connector and pull it straight out of its socket on the back of the logic board.

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Step 36

iMac Intel 21.5" EMC 2638 Power Supply Replacement: step 36, image 3 of 3

You may find it helpful to set the iMac down on its back for the next couple of steps.
Use the flat end of a spudger to press the clip on the side of the AC inlet cable connector inward.
While pressing on the release clip with the spudger, grasp the AC inlet cable, and pull the connector straight out of its socket.

Edit

Step 37

Remove the power supply from the iMac.

Edit

Conclusion

To reassemble your device, follow these instructions in reverse order.

14 other people completed this guide.

Author

with 4 other contributors

Sam Goldheart

Member since: 10/18/12

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One Comment

Great guide. My question is this however, How does one test this PSU before they replace it? I can't seem to find a PSU pinout for this particular unit (661-7111)

Stephen De Tomasi - Jan 16, 2017 Reply

iMac Intel 21.5" EMC 2638 Power Supply Replacement

Introduction

What you need

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