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.

Some models (with light sensor) have only the two outboard screws.

Robert Huber - Reply

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

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

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

  • The two leftmost 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: Image 2/2:
  • Rotate the center Phillips screw on the bottom of the iMac clockwise until the rear panel clamp contacts the edge of the case.

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Image 1/3: It will be necessary to work from alternate sides until the connector is free. Image 2/3: 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. 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, use a heavy duty spudger to pry the power supply connector away from its socket on the logic board.

  • 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 1/3: The power supply requires a large amount of force to remove.  You may need to bend the edge of the front case toward yourself for enough clearance to remove the power supply. Image 2/3: 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. Image 3/3: 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.
  • Lift the power supply slightly from its left edge, then grab each side and rotate the power supply toward yourself.

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

  • 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.

Smooth move not noting that there may be an ambient light sensor plugged into the board here. In the "large amount of force", I ended up yanking the cable right off the %$^@&$# sensor here - and took the contacts with the cable. So totally !@^@@& the thing up.

Matt Falcon - Reply

Quick tip: If you keep the captive screw on the right side held up, it helps a lot. Also, taking it completely out when reinserting the PSU helps a lot too.

coffee - Reply

Image 1/2: Pull the RAM chip straight away from its socket. Image 2/2: Repeat this process for the other RAM chip.
  • 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 rotated fully outward before installing new RAM chips.

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Image 1/1: One 11 mm T10 Torx.
  • Remove the following two screws:

    • One 11 mm T10 Torx.

    • One 10.6 mm T8 Torx.

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Image 1/1:
  • Lift the fan duct out of the chassis.

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Image 1/1:
  • Remove the two 7.3 mm Phillips screws securing the display data cable to the logic board.

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Image 1/1:
  • Pull the display cable up off the logic board by its black pull tab.

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Image 1/2: If you bend the pins on the logic board, use the fan connector as a guide to bend them straight. Image 2/2: If you bend the pins on the logic board, use the fan connector as a guide to bend them straight.
  • Disconnect both the left and right fan connectors by pulling them straight up off the logic board.

  • If you bend the pins on the logic board, use the fan connector as a guide to bend them straight.

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

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Image 1/1:
  • Remove the four 7 mm Phillips screws securing the optical drive to the midplane.

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Image 1/2: 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 2/2: 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.
  • Pull the optical drive up by its white pull tab to disconnect 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: Disconnect the speaker cable by pulling its connector straight up from the logic board. Image 2/2: Disconnect the speaker cable by pulling its connector straight up from the logic board.
  • Use the tip of a spudger to lift the speaker cable slightly.

  • Disconnect the speaker cable by pulling its connector straight up from the logic board.

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Image 1/2: Disconnect the fan and microphone cables by pulling their connectors straight up from the logic board. Image 2/2: Disconnect the fan and microphone cables by pulling their connectors straight up from the logic board.
  • Use the tip of a spudger to slightly lift the lower fan cable and microphone cable.

  • Disconnect the fan and microphone cables by pulling their connectors straight up from the logic board.

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Image 1/1:
  • Lift the AirPort card slightly by its plastic tab and pull it straight away from its socket.

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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 body of the AirPort card and its antenna connector.

  • 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.

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Image 1/1: Pull the AirPort antenna out from underneath the AirPort bracket.
  • Use a spudger to push the AirPort antenna through the gap in the AirPort bracket.

  • Pull the AirPort antenna out from underneath the AirPort bracket.

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Image 1/1:
  • Remove the two 5.5 mm T6 Torx screws securing the Bluetooth board to the logic board.

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Image 1/2: Be sure to only apply upward force, as any sideways force may cause the connector to shear off the Bluetooth board. Image 2/2: Use a spudger to pry the antenna connector off the Bluetooth board.
  • Use your finger to lift the Bluetooth board from the right edge up off its socket on the logic board.

  • Be sure to only apply upward force, as any sideways force may cause the connector to shear off the Bluetooth board.

  • Use a spudger to pry the antenna connector off the Bluetooth board.

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Image 1/1:
  • Disconnect the hard drive thermal sensor cable from the hard drive thermal sensor board.

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Image 1/1: One shouldered 12.4 mm Phillips.
  • Remove the following three screws:

    • One shouldered 12.4 mm Phillips.

    • Two 7 mm T10 Torx.

  • The two Torx screws may be Phillips in some units.

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Image 1/2: Twist the spudger to separate the SATA data connector from the hard drive, then disconnect it from the hard drive. Image 2/2: Repeat this process for the SATA power connector.
  • Insert the flat end of a spudger into the gap between the SATA data connector and the hard drive.

  • Twist the spudger to separate the SATA data connector from the hard drive, then disconnect it from the hard drive.

  • Repeat this process for the SATA power connector.

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Image 1/1:
  • Disconnect the black inverter cable from its socket on the logic board by pulling the cable straight away from its socket toward the side of the iMac.

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Image 1/1: Eight 7 mm T10 Torx.
  • Remove the following 9 screws securing the logic board to the midplane:

    • Eight 7 mm T10 Torx.

    • One 26 mm Phillips.

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Image 1/1:
  • Gently lift the logic board from its left side to clear the two pins mounted to the midplane.

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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 heat sink attached to the midplane. Image 2/2: We have a [guide|744|thermal paste guide] that makes applying thermal paste a snap.
  • Lift the logic board out of the midplane. Careful, there is a light guide on the lower left that can tear if you are not careful. This guides the light to the power-on light at the front of the iMac.

  • 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 heat sink attached to the midplane.

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

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Conclusion

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

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2 Comments

After removing and replacing the logic board on my iMac G5 twice, I thought I should add a suggestion.

Before replacing the board, it helps to tape or tie back all of the cables and connectors well out of the way. It's so easy to accidentally trap one of the connectors under the edge of the board. Also make sure to tie the speaker cables in a little bundle to make sure they fit into the small notch in the board/frame as it goes down.

One more item. When lowering the board into place, watch the small white plastic sleep light cone. The left of the two ears tend to get stuck on the edge of the (midplane?). It's difficult to see, but you can poke the end of a spurger in from the left to move the cone over just far enough to clear as the board is lowered. Make sure the holes in the sleep light cone ears are located over the little white matching pins. I made this mistake which caused me to remove the logic board, disturbing the thermal paste on the CPU.

randy3833 - Reply

My compliments to Andrew and everyone else who's been involved in this guide. I'd like to add my own suggestion regarding the 2

SATA cables and their routing. Make sure to A. Take a photo of any wiring routing prior to disassembly, and B. Note that the SATA power and data cables route UNDER the logic board as they pass from the HDD to their respective connectors on the logic board. I made the mistake of not paying attention and had to backtrack a bit to properly route those wires. Could / Would not have done this job without your guide so thank you very much!

ccarlley - Reply

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