Introduction

Like brain surgery? Use this guide to replace your logic board.

Image 1/1: Loosen the three Phillips screws securing the rear panel to the iMac.
  • Lay the iMac display-side down on a flat surface.

  • Loosen the three Phillips screws securing the rear panel to the iMac.

  • These screws are captive in the iMac. The center screw will stop turning after about 3.5 turns and the outer screws will stop turning after about 5.5 turns. Do not try to remove these screws from your iMac.

My iMac has only ONE catch, the central one, so the two outer screws are not to be touched.

In fact, I tried so hard to unscrew them, with a good screwdriver, that my hand hurt. Knowing that some times captive things (like these screws or a faucet) can be already at the end of their travel and we only lock them further into that position, I tried both screwing and unscrewing to no avail.

paulfrancoeur - Reply

That chick MJ is sexy!!!!!

djmadcracker - Reply

Looks like one of these screws is not like the others... a security Philips?! Never seen one of those before.

Terry Mullane - Reply

Please Note: If your iMac has an antenna for the airport extreme and not the bluetooth card. Don't buy the bluetooth get the airport extreme instead. Also, some newer devices may not work with these units.

James Janota - Reply

Just want to say thank you to ifixit! You guys are amazing and so helpful! This was so easy to do and I ordered the part I needed as well! We are up and running over here and my 7 year old son could not be any happier! Thank you!

mary nicolazzo - Reply

Image 1/3: Pull the rear panel toward yourself and remove it from the iMac. Image 2/3: Pull the rear panel toward yourself and remove it from the iMac. Image 3/3: Pull the rear panel toward yourself and remove it from the iMac.
  • Lift the rear panel slightly from the bottom edge of the iMac.

  • Pull the rear panel toward yourself and remove it from the iMac.

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Image 1/3: Pull the RAM chip straight away from its socket. Image 2/3: Repeat this process for the other RAM chip. Image 3/3: Be sure the RAM arms are fully rotated away from the RAM socket before reinstalling any RAM chips.
  • Rotate each of the two RAM retaining arms away from the RAM chip.

  • Pull the RAM chip straight away from its socket.

  • Repeat this process for the other RAM chip.

  • Be sure the RAM arms are fully rotated away from the RAM socket before reinstalling any RAM chips.

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Image 1/1:
  • Remove the three 8 mm brass Phillips screws securing the optical drive to the midplane.

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Image 1/3: Lift the free end of the optical drive just enough to clear the fan cover.  Lifting the free end of the optical drive too far may break the plastic positioning pins off the front bezel. Image 2/3: Lift the free end of the optical drive slightly, then pull it away from the edge of the rear case to clear the two plastic positioning pins. Image 3/3: Lift the optical drive out of your iMac.
  • Lift the optical drive near the connector to separate it from the logic board.

  • Lift the free end of the optical drive just enough to clear the fan cover. Lifting the free end of the optical drive too far may break the plastic positioning pins off the front bezel.

  • Lift the free end of the optical drive slightly, then pull it away from the edge of the rear case to clear the two plastic positioning pins.

  • Lift the optical drive out of your iMac.

  • When reinstalling your optical drive it may be necessary to set the bezel attached to the open end of the drive on the plastic positioning pins molded into the front bezel of the iMac and pull the connector side of the drive toward the edge of the rear case, bending it outward slightly, to properly seat the connector.

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Image 1/2: On our specific machine, the threaded portion of the clamp broke off the clamp body causing the center screw to turn without moving the bracket. If your machine is broken like ours, skip to the next step. Image 2/2: On our specific machine, the threaded portion of the clamp broke off the clamp body causing the center screw to turn without moving the bracket. If your machine is broken like ours, skip to the next step.
  • Rotate the center Phillips screw on the bottom of the iMac clockwise until the rear panel clamp contacts the edge of the case.

  • On our specific machine, the threaded portion of the clamp broke off the clamp body causing the center screw to turn without moving the bracket. If your machine is broken like ours, skip to the next step.

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Image 1/3: Twist the heavy duty spudger to slightly separate the connector from its socket. Image 2/3: It will be necessary to work from alternate sides until the connector is free. Image 3/3: Your power supply may have an ambient light sensor cable attached from the power supply to the logic board. If so, carefully use a spudger to push out the cable towards you using the sides of the cable alternatively to help you slide it out.
  • While depressing the connector lock, insert the flat end of a heavy duty spudger into the gap between the power supply connector and its socket.

  • Twist the heavy duty spudger to slightly separate the connector from its socket.

  • It will be necessary to work from alternate sides until the connector is free.

  • Your power supply may have an ambient light sensor cable attached from the power supply to the logic board. If so, carefully use a spudger to push out the cable towards you using the sides of the cable alternatively to help you slide it out.

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Image 1/1: This step is very simple if you remove the power supply first.
  • Pull the power supply connector straight away from its socket on the logic board.

  • This step is very simple if you remove the power supply first.

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Image 1/1: All three screws are captive in the power supply.
  • Remove the three Phillips screws securing the power supply to the chassis.

  • All three screws are captive in the power supply.

  • To aid in removal, it may be helpful to lift the center screw slightly away from the midplane.

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Image 1/2: Grab the power supply from each side and rotate its top edge toward yourself until it clears the logic board. Image 2/2: Lift the power supply out of the midplane.
  • There are several capacitors mounted to the logic board in close proximity to the power supply. Try not to disturb them, as they are delicate and may break off the board.

  • Grab the power supply from each side and rotate its top edge toward yourself until it clears the logic board.

  • Lift the power supply out of the midplane.

  • The power supply requires a large amount of force to remove. You may need to slightly bend the edge of the front case toward yourself for enough clearance to remove the power supply.

Bend the case at the rear panel clamp enough to clear the panel clamp while lifting out the power supply using the two captive screws as handles.

timothychilders - Reply

Rolling the power supply towards you while lifting using the captive screws helps get it past the captive back cover screw from step 4.

themackey - Reply

My replacement power supply did not come with an Ambient Light Sensor. I thought I had gotten the wrong one, but in fact the ALS comes easily off the old power supply (using a small flathead screwdriver to pry it off) and attaches to the new one.

Calion - Reply

Image 1/1: During reassembly, use the tip of your spudger to plug the hard drive thermal sensor back into the socket on the hard drive thermal sensor board.
  • Disconnect the hard drive thermal sensor cable from the hard drive thermal sensor board.

  • During reassembly, use the tip of your spudger to plug the hard drive thermal sensor back into the socket on the hard drive thermal sensor board.

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Image 1/2: Lift the fan duct out of the midplane. Image 2/2: Lift the fan duct out of the midplane.
  • Remove the two 13 mm T10 Torx screws securing the fan duct to the midplane.

  • Lift the fan duct out of the midplane.

The screws are T10, not T8

Yishai Sered - Reply

Quote from Yishai Sered:

The screws are T10, not T8

Mine are T10.

Yishai Sered - Reply

On the ALS model, the left arm is longer/straight and combines with one of the logic board fixings, which is why you will only have 5 torx screws to take out in the final stage. When re-assembling be sure not to use this as a fixing point until the duct is fitted back in.

harwood - Reply

Image 1/2: The shouldered Phillips screw belongs in the lower left corner of the fan cover. Image 2/2: Lift the fan cover out of the midplane.
  • Remove the two Phillips screws securing the fan cover to the midplane.

  • The shouldered Phillips screw belongs in the lower left corner of the fan cover.

  • Lift the fan cover out of the midplane.

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Image 1/2: Using its black pull tab, pull the display data cable connector straight up off its socket on the logic board. Image 2/2: Using its black pull tab, pull the display data cable connector straight up off its socket on the logic board.
  • Remove the two 7 mm shouldered Phillips screws securing the display data cable to the logic board.

  • Using its black pull tab, pull the display data cable connector straight up off its socket on the logic board.

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Image 1/1: Pull the connector parallel to the face of the logic board.
  • Disconnect the SATA power cable by depressing the lock mechanism and pulling the connector straight away from its socket.

  • Pull the connector parallel to the face of the logic board.

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Image 1/1:
  • Disconnect the SATA data cable by pulling its connector straight up off the logic board.

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Image 1/2: The larger of the two fans connects closest to the top edge of the logic board. Image 2/2: On the ALS model, the larger fan connector is attached with a clip. Depress the clip while carefully removing the plug.
  • Disconnect both fans by pulling their connectors straight up off the logic board.

  • The larger of the two fans connects closest to the top edge of the logic board.

  • On the ALS model, the larger fan connector is attached with a clip. Depress the clip while carefully removing the plug.

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Image 1/1:
  • Slide the inverter-to-display cable connector from under the metal clip on the midplane.

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Image 1/1:
  • Disconnect the inverter-to-display cable connector by pulling it straight away from its socket.

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Image 1/2: Lift the inverter straight up off the pins on the logic board. Image 2/2: Be sure to lift the inverter straight up off the logic board, as the connector pins are very long and easily bent. If the pins bend during removal, use the connector on the inverter as a guide to bend them straight.
  • Remove the single 8 mm brass Phillips screw securing the inverter to the logic board.

  • Lift the inverter straight up off the pins on the logic board.

  • Be sure to lift the inverter straight up off the logic board, as the connector pins are very long and easily bent. If the pins bend during removal, use the connector on the inverter as a guide to bend them straight.

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Image 1/1:
  • Disconnect the inverter cable from the logic board by pulling it straight up from its socket.

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Image 1/1: Lift the inverter out of the midplane and set it aside.
  • De-route the inverter cable connector from the channel in the logic board.

  • Lift the inverter out of the midplane and set it aside.

  • Skip this step if yours is an ALS model; this part is not present.

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Image 1/1: If you do bend the pins during removal, use the connectors as a guide to bend them back straight.
  • The connectors removed in the next few steps slide onto long pins attached to the logic board. Be sure to only pull them straight up from the logic board to avoid bending the pins.

  • If you do bend the pins during removal, use the connectors as a guide to bend them back straight.

  • Use the tip of a spudger to lift the speaker cable connector from its lower edge straight up off the logic board.

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Image 1/2: With the spudger still inserted, lift the lower fan connector straight up off the logic board. Image 2/2: The speaker cable connector attaches to the pins closest to the power supply. It is the only connector with four wires. The microphone cable attaches to the pins furthest away from the power supply and is the only connector with a dark orange wire.
  • Insert the tip of a spudger into the center hole punched into the side of the lower fan connector.

  • With the spudger still inserted, lift the lower fan connector straight up off the logic board.

  • The speaker cable connector attaches to the pins closest to the power supply. It is the only connector with four wires. The microphone cable attaches to the pins furthest away from the power supply and is the only connector with a dark orange wire.

Doesn't this mean speaker connector - not fan connector?

harwood - Reply

ALS model looks different from this

harwood - Reply

Image 1/1:
  • Use the tip of a spudger to lift the microphone cables enough to grab the microphone cable connector and pull it straight up off the logic board.

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Image 1/1: This step does not apply to the ALS model; this bracket is not present. The card attaches with a pair of T6 Torx screws and looks slightly different from this picture.
  • Using its attached pull tab, lift the AirPort card slightly and pull it straight away from its socket.

  • This step does not apply to the ALS model; this bracket is not present. The card attaches with a pair of T6 Torx screws and looks slightly different from this picture.

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Image 1/1: Push the spudger away from the AirPort card to disconnect the AirPort antenna.
  • Insert the flat end of a spudger between the antenna connector and the body of the AirPort card.

  • Push the spudger away from the AirPort card to disconnect the AirPort antenna.

  • When reassembling your iMac, be sure to insert the AirPort card the way it was before disassembly.

  • This step does not apply to the ALS model.

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Image 1/2: De-route the AirPort antenna out from under the AirPort bracket. Image 2/2: This step does not apply to the ALS model.
  • Use a spudger to push the AirPort antenna cable through the slot in the AirPort card bracket.

  • De-route the AirPort antenna out from under the AirPort bracket.

  • This step does not apply to the ALS model.

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Image 1/1: Some models may not have a blue tooth module.
  • Remove the two T6 Torx screws securing the Bluetooth board to the logic board.

  • Some models may not have a blue tooth module.

My iMac doesn't have the BlueTooth card. Instead, the antenna is connected to the board with a plastic clip which is easy to remove and reattach.

Mark - Reply

Image 1/2: Be sure to lift the Bluetooth board from its right edge only.  Trying to lift it up from any other side will shear the connector off the Bluetooth board. Image 2/2: Use the flat end of a spudger to pry the Bluetooth antenna connector up off the Bluetooth board.
  • Depending on your iMac model, the bluetooth board may be blue. Use your fingertip to lift the Bluetooth board from its right edge, disconnecting it from its socket on the logic board.

  • Be sure to lift the Bluetooth board from its right edge only. Trying to lift it up from any other side will shear the connector off the Bluetooth board.

  • Use the flat end of a spudger to pry the Bluetooth antenna connector up off the Bluetooth board.

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Image 1/1: Six 7 mm T10 Torx.
  • Remove the following nine screws securing the logic board to the midplane:

    • Six 7 mm T10 Torx.

    • Three long 20 mm brass coarse-thread Phillips.

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Image 1/2: Image 2/2:
  • Lift the logic board from its left edge to clear the two positioning pins connected to the midplane.

On my ALS model there is a cable connector marked 'fan 1' lower right of the G5 box.

harwood - Reply

Image 1/2: When reinstalling your logic board, be sure to clean and apply a new layer of thermal paste to the U3 chip (highlighted in red) located on the underside of your logic board as well as its copper heat sink attached to the midplane. Image 2/2: We have a [guide|744|thermal paste guide] that makes applying thermal paste a snap.
  • Grab the logic board from both edges and lift it out of the midplane, minding any cables that may get caught.

  • When reinstalling your logic board, be sure to clean and apply a new layer of thermal paste to the U3 chip (highlighted in red) located on the underside of your logic board as well as its copper heat sink attached to the midplane.

  • We have a thermal paste guide that makes applying thermal paste a snap.

There is a white support foot under the board directly behind the speaker. If this comes free with the board, it should be placed on the frame using the locating plastic nipples before replacing the board. Do not attach it to the board and try to push it back down as there is in sufficient space for it to pass through.

harwood - Reply

Conclusion

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

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