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iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement

What you need

  1. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement, Display Assembly: step 1, image 1 of 1
    Tool used on this step:
    iMac Intel 21.5" Cardboard Service Wedge
    $4.99
    Buy
    • 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.

  2. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 2, image 1 of 2 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 2, image 2 of 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.

  3. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 3, image 1 of 3 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 3, image 2 of 3 iMac Intel 21.5" Retina 4K Display (2017) CPU 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.

  4. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 4, image 1 of 3 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 4, image 2 of 3 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 4, image 3 of 3
    • Continue running the tool up around the top left corner.

  5. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 5, image 1 of 2 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 5, image 2 of 2
    • Cut the adhesive along the top left of the display.

  6. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 6, image 1 of 2 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 6, image 2 of 2
    • 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.

  7. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 7, image 1 of 3 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 7, image 2 of 3 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 7, image 3 of 3
    • Push the tool around the top right corner of the display.

  8. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 8, image 1 of 2 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 8, image 2 of 2
    • Wheel the tool down along the right side of the display.

  9. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 9, image 1 of 2 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 9, image 2 of 2
    • 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.

  10. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 10, image 1 of 3 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 10, image 2 of 3 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 10, image 3 of 3
    Tool used on this step:
    Plastic Cards
    $2.99
    Buy
    • 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.

  11. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 11, image 1 of 2 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 11, image 2 of 2
    • 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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    • 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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    • 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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    • Insert a second plastic card into the gap between the display and frame near the top left corner of the iMac.

  15. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 15, image 1 of 2 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 15, image 2 of 2
    • 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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    • Slide the plastic card toward the center, again stopping just before the iSight camera.

  17. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 17, image 1 of 2 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 17, image 2 of 2
    • Wedge the plastic card back into the top left corner.

  18. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 18, image 1 of 3 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 18, image 2 of 3 iMac Intel 21.5" Retina 4K Display (2017) CPU 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.

  19. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement, Display Assembly Cables: step 19, image 1 of 2 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement, Display Assembly Cables: step 19, image 2 of 2
    • 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").

    • Hold the display with one hand while using your other hand to unplug the display power cable.

  20. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 20, image 1 of 3 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 20, image 2 of 3 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 20, image 3 of 3
    • Continuing to support the display with one hand, 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, keeping it parallel to the motherboard, to avoid damaging it.

  21. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement, Display Assembly Separation: step 21, image 1 of 2 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement, Display Assembly Separation: step 21, image 2 of 2
    • 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.

  22. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 22, image 1 of 3 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 22, image 2 of 3 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 22, image 3 of 3
    Tool used on this step:
    Plastic Cards
    $2.99
    Buy
    • 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.

  23. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 23, image 1 of 3 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 23, image 2 of 3 iMac Intel 21.5" Retina 4K Display (2017) CPU 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.

    • After the adhesive is cut, it cannot be used to re-seal the display in place. Follow this guide to replace the adhesive strips that secure the display to the rear enclosure.

  24. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement, Lower Support Bracket: step 24, image 1 of 2 iMac Intel 21.5" Retina 4K Display (2017) CPU 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

    • You may need to peel up the display adhesive lining the bottom edge of the iMac enclosure to access the screws.

  25. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 25, image 1 of 1
    • Remove the lower support bracket (a.k.a. "chin strap") from the iMac enclosure.

  26. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement, Hard Drive Brackets: step 26, image 1 of 1
    • Remove the following T10 Torx screws securing the hard drive brackets to the iMac:

    • Two 21 mm screws

    • One 9 mm screw

    • One 27 mm screw

  27. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 27, image 1 of 2 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 27, image 2 of 2
    • Remove the left and right hard drive brackets from the iMac.

  28. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement, Power Supply: step 28, image 1 of 3 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement, Power Supply: step 28, image 2 of 3 iMac Intel 21.5" Retina 4K Display (2017) CPU 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.

  29. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 29, image 1 of 2 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 29, image 2 of 2
    • 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.

  30. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 30, image 1 of 1
    • Remove the two 7.2 mm T8 Torx screws securing the power supply to the rear enclosure.

  31. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 31, image 1 of 2 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 31, image 2 of 2
    • 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.

  32. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 32, image 1 of 3 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 32, image 2 of 3 iMac Intel 21.5" Retina 4K Display (2017) CPU 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.

  33. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 33, image 1 of 2 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 33, image 2 of 2
    • Slide the power supply to the right to clear the screw posts on the rear enclosure.

  34. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 34, image 1 of 3 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 34, image 2 of 3 iMac Intel 21.5" Retina 4K Display (2017) CPU 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.

  35. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 35, image 1 of 3 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 35, image 2 of 3 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 35, image 3 of 3
    • 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.

    • Do not let any of the exposed solder joints come in contact with a metal surface, as that can cause a short.

    • Flip the power supply over to access the DC power cable connection behind the logic board.

    • To disconnect the cable, squeeze the release clip on the back side of the connector, behind the logic board, and pull the connector straight out.

  36. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 36, image 1 of 3 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 36, image 2 of 3 iMac Intel 21.5" Retina 4K Display (2017) CPU 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 release 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.

  37. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 37, image 1 of 1
    • Remove the power supply from the iMac.

  38. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement, Fan: step 38, image 1 of 2 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement, Fan: step 38, image 2 of 2
    • Gently pull the fan cable connector straight out of its socket on the logic board.

  39. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 39, image 1 of 1
    • Remove the three 10 mm T10 Torx screws securing the fan to the rear enclosure.

    • The uppermost screw has a rubber standoff adhered to its head to support the display—leave this in place.

  40. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 40, image 1 of 2 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 40, image 2 of 2
    • Remove the fan from the iMac.

  41. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement, Hard Drive Assembly: step 41, image 1 of 3 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement, Hard Drive Assembly: step 41, image 2 of 3 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement, Hard Drive Assembly: step 41, image 3 of 3
    • Lift the hard drive from the edge nearest the logic board and pull it slightly out of its recess.

    • The hard drive is attached by a single SATA power/data cable—do not attempt to fully remove it from the iMac yet.

  42. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 42, image 1 of 2 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 42, image 2 of 2
    • Use a spudger to disconnect the single SATA power and data combo cable by gently prying its large plastic connector away from the hard drive.

  43. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 43, image 1 of 1
    • Remove the hard drive assembly from the iMac.

  44. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement, Hard Drive Tray: step 44, image 1 of 1
    • Remove the 7.3 mm T8 Torx screw securing the hard drive tray to the rear enclosure.

  45. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 45, image 1 of 1
    • Remove the hard drive tray.

  46. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement, Logic Board Assembly: step 46, image 1 of 2 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement, Logic Board Assembly: step 46, image 2 of 2
    • Gently pull the left speaker cable straight out of its socket on the logic board.

  47. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 47, image 1 of 1
    • De-route the left speaker cable by pulling it straight up out of the retaining clip in the back of the rear enclosure.

  48. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 48, image 1 of 2 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 48, image 2 of 2
    • Similarly to the previous step, de-route the SATA and power cables by pulling the braid straight up out of the retaining clip.

  49. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 49, image 1 of 2 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 49, image 2 of 2
    • Peel up the piece of tape connecting the left speaker connector to the SATA power and data cables.

  50. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 50, image 1 of 3 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 50, image 2 of 3 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 50, image 3 of 3
    • Flip up the metal retaining bracket on the FaceTime camera cable connector.

    • Pull the FaceTime camera cable straight out of its socket on the logic board.

    • This is a delicate connector that can be easily damaged.

  51. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 51, image 1 of 1
    • Remove the two 4.0 mm T5 Torx screws securing the four antenna connectors to the AirPort/Bluetooth card.

  52. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 52, image 1 of 3 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 52, image 2 of 3 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 52, image 3 of 3
    • Disconnect all four antenna connectors by prying them straight up from their sockets on the AirPort/Bluetooth card.

  53. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 53, image 1 of 2 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 53, image 2 of 2
    • Gently pull the right speaker cable connector straight down and out of its socket on the logic board.

  54. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 54, image 1 of 3 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 54, image 2 of 3 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 54, image 3 of 3
    • Use the flat edge of a spudger to pry the headphone jack cable connector from its socket on the logic board.

    • Push the cable slightly to the right.

  55. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 55, image 1 of 1
    • Peel off the tape covering the exhaust duct.

  56. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 56, image 1 of 1
    • Remove the following T8 Torx screws securing the exhaust duct to the rear enclosure:

    • Two 6.2 mm screws

    • Two 4.7 mm screws

  57. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 57, image 1 of 3 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 57, image 2 of 3 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 57, image 3 of 3
    • Use the tip of a spudger to flip open the retaining flap on the microphone ribbon cable ZIF socket.

    • Be sure you are prying up on the hinged retaining flap, not the socket itself.

    • Gently pull the microphone ribbon cable straight out of its socket.

  58. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 58, image 1 of 1
    • Remove the four 7.3 mm T8 Torx screws securing the logic board to the rear enclosure.

  59. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 59, image 1 of 3 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 59, image 2 of 3 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 59, image 3 of 3
    • Tilt the top of the logic board away from the rear enclosure.

    • As you tilt the logic board, pull the right speaker connector to the right and out of the way of the board.

    • Lift the logic board straight up and out of the iMac.

    • Be careful not to snag the board on any of the rear enclosure's screw posts.

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    • When reassembling your iMac, be very careful to align the exterior I/O ports correctly. The logic board can sit crooked even when secured with all its screws.

    • Use a USB flash drive and/or ethernet cable to keep the logic board seated correctly while you tighten the screws.

  61. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement, SATA Data and Power Cables: step 61, image 1 of 3 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement, SATA Data and Power Cables: step 61, image 2 of 3 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement, SATA Data and Power Cables: step 61, image 3 of 3
    • The SATA data connector has a clip that must be pressed to allow removal.

    • While pressing on the clip with your thumb, lift and disconnect the SATA data connector from its socket on the logic board.

  62. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 62, image 1 of 2 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 62, image 2 of 2
    • Grasp the hard drive power connector and gently pull it out of its socket on the logic board.

  63. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement, Heat Sink Assembly: step 63, image 1 of 2 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement, Heat Sink Assembly: step 63, image 2 of 2
    • Peel off the four black tamper-evident stickers covering the heat sink mounting screws.

    • Remove the four T10 screws that secure the heat sink from the backside of the logic board.

    • During reassembly, tighten these screws one full turn at a time, alternating in a cross pattern. This will gradually increase the clamping pressure evenly across the surface of the CPU. Continue gradually tightening the screws until they're snug and the entire spring plate lays flat against the logic board.

  64. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 64, image 1 of 2 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 64, image 2 of 2
    • Lift the heat sink retaining spring and its bracket off the logic board.

  65. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 65, image 1 of 1
    • Fully loosen the three captive T8 screws securing the heat sink over the GPU.

    • Remove the two 5.4 mm T8 screws securing the heat pipe to the logic board.

  66. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 66, image 1 of 2 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 66, image 2 of 2
    • Note that the CPU will most likely remain stuck to the underside of the heat sink as it's lifted out. Take care not to damage it.

    • Lift and remove the heat sink assembly from the logic board.

  67. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement, CPU: step 67, image 1 of 1
    • Flip the heat sink over and use your spudger to pry out the CPU, being careful not to drop it.

    • A thick layer of thermal paste holds the CPU in place.

  68. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 68, image 1 of 1
    • Lift and remove the CPU from the heat sink.

  69. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 69, image 1 of 2 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 69, image 2 of 2
    • Use a lint-free cloth (or coffee filter) with either isopropyl alcohol or ArctiClean Thermal Material Remover to thoroughly clean the thermal paste residue from both the CPU and GPU arms of the heat sink.

    • Once the heat sink surfaces are completely clean, use a fresh lint-free cloth or coffee filter to apply a drop of ArctiClean Thermal Surface Purifier to remove any oils and prepare the copper heat sink surfaces.

    • Do not touch the copper surface with your bare fingers, or allow any dust or debris to get on it. Even a fingerprint can be a major obstacle to thermal transfer. If you touch it accidentally, re-clean it and re-apply the surface purifier.

    • Allow the heat sink to dry completely while you continue working.

  70. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 70, image 1 of 2 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 70, image 2 of 2
    • Use a spudger to gently lift the excess thermal paste residue off of the GPU.

    • As before, use a lint-free cloth or coffee filter and the appropriate fluids to clean and prep the GPU surface.

    • Clean the thermal paste from the four VRAM chips around the GPU as well.

  71. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 71, image 1 of 2 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 71, image 2 of 2
    • Apply thermal pads to the four VRAM modules around the GPU.

    • Alternatively, you can use a thick thermal paste such as K5-PRO.

    • Use tweezers to peel the liner from the tops of the thermal pads.

  72. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 72, image 1 of 2 iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 72, image 2 of 2
    • Check the orientation of your CPU before installing it.

    • Small cutouts on the edges of the CPU align with notches on the sides of the socket.

    • Carefully align your new CPU into its socket on the motherboard, and lay it into position.

  73. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 73, image 1 of 1
  74. iMac Intel 21.5" Retina 4K Display (2017) CPU Replacement: step 74, image 1 of 1
    • Apply a thin bead of thermal paste to the GPU.

    • You do not need to apply any thermal paste to the heat sink, although Arctic Silver does suggest "tinting" the surface of the heat sink. For more information on this and on thermal paste application in general, see Arctic Silver's instructions.

    • You can now reinstall the heat sink over the CPU and GPU.

Adam O'Camb

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