Danger
Potentially Dangerous
Injury may result if this procedure is not followed properly. Use caution and follow all warnings.
Danger

Introduction

Follow this guide to replace the PRAM battery in a 21.5" Retina 4K Late 2015 iMac. The PRAM battery is located on the back side of the logic board, so replacing it requires first removing the logic board.

  • 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.

  • 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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Image 1/2: 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. Image 2/2: 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.
  • 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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Image 1/3: Be sure to always push with the handle behind the cutting wheel. If you pull, the wheel might get pulled out of the handle. Image 2/3: Run the tool up along the left side of the display. Image 3/3: Run the tool up along the left side of the display.
  • 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.

Erreur de traduction: "de bas en haut" et non de" haut en bas" sur le côté gauche de l'écran

Moreau - Reply

Image 1/3: Image 2/3: Image 3/3:
  • Continue running the tool up around the top left corner.

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Image 1/2: Image 2/2:
  • Cut the adhesive along the top left of the display.

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Image 1/2: 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. Image 2/2: 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.
  • 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.

In this step can I cut along the display without make any damage to the front camera?

arisnordico - Reply

Hi! Actually - there is no need to cut the tape around the camera area - there is no tape to cut at all! And so, the way go is easy - just pass 10 mm to the left and to the right from camera and start cutting!

P.S. Just did the whole procedure to replace a RAM and to add SSD on PSIe an hour ago! Seems to be different reading the instructions... you know - 2/10 and so on. But it's really not that hard, trust me. I'll give it 5/10.

P.P.S. By the way there is one trick to pass the difficult steps. Any action which requires pulling smth (motherboard, speaker, power supply unit) from the narrow crack (or should i say - slit?) at the bottom of your Imac is really not so easy.

And the trick is to first remove a thin metal stripe with some kind of insulation on it which held by 5 small (very small!!) screws at the bottom of your Imac. After you done it - it's easy to pull everything! Pay attention to the fact that one of this 5 screws at the center are more shortly than others.

dv1977 - Reply

After doing the replacement the adhesive still sticks quite good enough to hold the screen in place. Maybe this isn't rock-solid, but enough for me.

Mirko - Reply

I did all steps like this manuell but now the Display wont work only some colered strips are to see! Whats happend??

Can anybody help me ? Maybe the connector cable is broken?

djfanta - Reply

Check both connectors, probably one of them not seated well

pzhivulin -

You can add a SATA SSD if you already have a PCIe SSD Factory?

kaserlik - Reply

If you're changing cracked EMC 2638 display to new assembly, there's two more steps:

Step 24: 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 display assembly.

Step 25: Use the tip of a spudger to unplug bracket of the thermal sensor small cable near display data cable.

Carefully remove scotch tape covering thermal sensor. Using iSesamo or flat tip of the spudger carefully peel the thermal sensor away.

pzhivulin - Reply

omg - forgot to switch the termal sensor from the old display...

now fan runs like crazy...

Andrei Balotescu -

Image 1/3: Image 2/3: Image 3/3:
  • Push the tool around the top right corner of the display.

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Image 1/2: Image 2/2:
  • Wheel the tool down along the right side of the display.

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Image 1/2: At this point, you'll want to run the tool back around the entire display, to ensure you cut as much adhesive as possible. Image 2/2: At this point, you'll want to run the tool back around the entire display, to ensure you cut as much adhesive as possible.
  • 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.

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Image 1/3: Set the iMac face-up on a table. Image 2/3: Starting from the top right corner of the iMac, wedge a plastic card between the display and frame. Image 3/3: Be careful '''not''' to insert the plastic card more than 3/8", or you may damage internal components.
  • 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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Image 1/2: Move slowly and be careful not to stress the display glass too much—you only need to make a gap of about 1/4". Image 2/2: Move slowly and be careful not to stress the display glass too much—you only need to make a gap of about 1/4".
  • 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".

This part must be done very carefully or you can damage the flat cable from display, despite it was under a iron cover.

Cassio Machado - Reply

Image 1/3: Be sure to '''stop''' before the iSight camera, or you may damage it. Image 2/3: Be sure to '''stop''' before the iSight camera, or you may damage it. Image 3/3: Be sure to '''stop''' before the iSight camera, or you may damage it.
  • 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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Image 1/2: Image 2/2:
  • 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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Image 1/3: Image 2/3: Image 3/3:
  • 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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Image 1/2: As with the other side, twist slowly to allow the adhesive time to separate, and be careful not to over-stress the display glass. Image 2/2: As with the other side, twist slowly to allow the adhesive time to separate, and be careful not to over-stress the display glass.
  • 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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Image 1/3: Image 2/3: Image 3/3:
  • Slide the plastic card toward the center, again stopping just before the iSight camera.

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Image 1/2: Image 2/2:
  • Wedge the plastic card back into the top left corner.

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Image 1/3: 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. Image 2/3: Begin to lift the top of the display up from the frame. Image 3/3: Only lift the display a few inches—the display data and power cables are still connected to the logic board.
  • 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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Image 1/2: Hold the display with one hand while using your other hand to unplug the display power cable. Image 2/2: Hold the display with one hand while using your 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").

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

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Image 1/3: Carefully pull the display data cable from its socket on the logic board. Image 2/3: Be sure to pull the display data cable connector straight out of its socket, keeping it parallel to the motherboard, to avoid damaging it. Image 3/3: Be sure to pull the display data cable connector straight out of its socket, keeping it parallel to the motherboard, to avoid damaging it.
  • 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.

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Image 1/2: 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. Image 2/2: 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.
  • 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.

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Image 1/2: Image 2/2:
  • If necessary, a plastic card can be used to cut any remaining sections of the bottom adhesive strip.

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Image 1/3: It may be necessary to slowly lift from one side to peel against the remaining adhesive. Image 2/3: Be very careful handling the display—it's big, heavy, and made of glass. Image 3/3: After the adhesive is cut, it cannot be used to re-seal the display in place. Follow [https://www.ifixit.com/Guide/iMac+Intel+21.5-Inch+Retina+4K+Display+Adhesive+Strips+Replacement/64210|this guide|new_window=true] to replace the adhesive strips that secure the display to the rear enclosure.
  • 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.

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Image 1/2: Four 3.2 mm screws Image 2/2: One 1.7 mm screw
  • 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.

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Image 1/1:
  • Remove the lower support bracket from the iMac enclosure.

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Image 1/2: Image 2/2:
  • Gently pull the right speaker cable connector straight down and out of its socket on the logic board.

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Image 1/1: Rubber washers keep the screws snug in the speaker even when loosened. You can use tweezers  or a fingernail to remove the screws, or simply leave them with the speaker assembly.
  • Remove the two 10 mm T10 Torx screws securing the right speaker to the rear enclosure.

    • Rubber washers keep the screws snug in the speaker even when loosened. You can use tweezers or a fingernail to remove the screws, or simply leave them with the speaker assembly.

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Image 1/3: If the channel is not easily accessible, you can tip the speaker slightly forward (away from the rear case) to gain access to the antenna cable. Image 2/3: If the channel is not easily accessible, you can tip the speaker slightly forward (away from the rear case) to gain access to the antenna cable. Image 3/3: If the channel is not easily accessible, you can tip the speaker slightly forward (away from the rear case) to gain access to the antenna cable.
  • Insert the tip of a spudger between the right speaker and the antenna cable, running it down the right side of the speaker to de-route the cable from its channel.

  • If the channel is not easily accessible, you can tip the speaker slightly forward (away from the rear case) to gain access to the antenna cable.

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Image 1/3: Pull the speaker straight up and remove it from the iMac. Image 2/3: Pull the speaker straight up and remove it from the iMac. Image 3/3: Pull the speaker straight up and remove it from the iMac.
  • Tip the right speaker forward out of the rear enclosure, about 1 cm.

  • Pull the speaker straight up and remove it from the iMac.

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Image 1/1: Two 21 mm screws
  • 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

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Image 1/2: Image 2/2:
  • Remove the left and right hard drive brackets from the iMac.

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Image 1/3: Use the tip of a spudger to push each side of the power button cable connector and gently ''walk'' it out of its socket. Image 2/3: Use the tip of a spudger to push each side of the power button cable connector and gently ''walk'' it out of its socket. Image 3/3: Use the tip of a spudger to push each side of the power button cable connector and gently ''walk'' it out of its socket.
  • 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.

I would advise that before removing the PSU unit and all other components from the bottom of the case that you remove the 5 screws at the bottom of the display which hold an insulation strip in place.

The guide shows this piece removed, but does not tell you how to remove it.

There will be 5, small J1000 screws. The middle one, which goes over Apple Logo is the shorter one of the 5, all others are the same length. Once this piece is gone removing the components is much easier, and chance of damage lessened.

Jeffrey Gelinas - Reply

Added to the guide. Thanks for the tip!

Jeff Suovanen -

No need to remove power board and logic board and all other components, just remove the fan and it is quite "easily" accessable to change the RAM. Just need to use the tools to remove the old RAM and carefully install the new RAM.

I just did it without removing the logic or power board

Oleksandr Trokhymchuk - Reply

Image 1/2: Image 2/2:
  • 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.

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Image 1/1: In newer model iMacs these are 7.2 mm T8 or T9 Torx screws.
  • 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 or T9 Torx screws.

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Image 1/2: Tilt the power supply forward. Image 2/2: Tilt the power supply forward.
  • 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.

When replacing the PSU (on the re-build) take care not to trap the power button cable behind it - I did...

Dave Hallett - Reply

Image 1/3: Rotate the power supply counterclockwise, lifting the right side up about an inch higher than the left. Image 2/3: Rotate the power supply counterclockwise, lifting the right side up about an inch higher than the left. Image 3/3: Rotate the power supply counterclockwise, lifting the right side up about an inch higher than the left.
  • 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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Image 1/2: Image 2/2:
  • Slide the power supply to the right to clear the screw posts on the rear enclosure.

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Image 1/3: '''Do not''' try to completely remove the power supply from the iMac yet—it is still connected to the logic board. Image 2/3: '''Do not''' try to completely remove the power supply from the iMac yet—it is still connected to the logic board. Image 3/3: '''Do not''' try to completely remove the power supply from the iMac yet—it is still connected to the logic board.
  • 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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Image 1/2: Flip the power supply over to access the DC power cable connection behind the logic board. Image 2/2: Squeeze the DC power cable connector tab and pull it straight out of its socket on the back of the logic board.
  • 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 DC power cable connector tab and pull it straight out of its socket on the back of the logic board.

when pulled the cable, even slightly, the actual female piece that connects to the logic board came off. am i screwed?

Racheal Major - Reply

Image 1/3: Use the flat end of a spudger to press the clip on the side of the AC inlet cable connector inward. Image 2/3: While pressing on the release clip with the spudger, grasp the AC inlet cable, and pull the connector straight out of its socket. Image 3/3: While pressing on the release clip with the spudger, grasp the AC inlet cable, and pull the connector straight out of its socket.
  • 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.

I didn't disconnect the input cable to the power supply. Because I had the machine lying on its back throughout, I placed it on to the metal bit at the bottom of the machine instead (with a cloth to stop the metal getting scratched). The AC inlet cable was pretty tricky to get un-locked, and the PSU sat on the case fine. It didn't hinder anything else throughout the guide.

Dave Hallett - Reply

Image 1/1:
  • Remove the power supply from the iMac.

erreur: retirer "la carte d'alimentation" et non" le disque dur" !!!!!

Moreau - Reply

Image 1/2: Image 2/2:
  • Gently pull the fan cable connector straight out of its socket on the logic board.

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Image 1/1: The uppermost screw has a rubber standoff adhered to its head to support the display—leave this in place.
  • 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.

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Image 1/2: Image 2/2:
  • Remove the fan from the iMac.

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Image 1/3: The hard drive is attached by a single SATA power/data cable—do '''not''' attempt to fully remove it from the iMac yet. Image 2/3: The hard drive is attached by a single SATA power/data cable—do '''not''' attempt to fully remove it from the iMac yet. Image 3/3: The hard drive is attached by a single SATA power/data cable—do '''not''' attempt to fully remove it from the iMac yet.
  • 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.

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Image 1/2: Image 2/2:
  • 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.

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Image 1/1:
  • Remove the hard drive assembly from the iMac.

When reassembling, I found it easier to loosen the HD tray screw from Step 48 and pull the tray outwards from the left side in order to plug the SATA cable in more easily.

KB1972 - Reply

Thanks! I, too, had a hard time reconnecting the SATA cable.

boboswell -

Image 1/1:
  • Remove the 7.3 mm T8 Torx screw securing the hard drive tray to the rear enclosure.

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Image 1/1:
  • Remove the hard drive tray.

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Image 1/2: Image 2/2:
  • Gently pull the left speaker cable straight out of its socket on the logic board.

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Image 1/1:
  • De-route the left speaker cable by pulling it straight up out of the retaining clip in the back of the rear enclosure.

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Image 1/2: Image 2/2:
  • Similarly to the previous step, de-route the SATA and power cables by pulling the braid straight up out of the retaining clip.

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Image 1/2: Image 2/2:
  • Peel up the piece of tape connecting the left speaker connector to the SATA power and data cables.

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Image 1/3: Pull the FaceTime camera cable straight out of its socket on the logic board. Image 2/3: This is a delicate connector that can be easily damaged. Image 3/3: This is a delicate connector that can be easily damaged.
  • 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.

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Image 1/1:
  • Remove the two 4.0 mm T5 Torx screws securing the four antenna connectors to the AirPort/Bluetooth card.

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Image 1/3: Image 2/3: Image 3/3:
  • Disconnect all four antenna connectors by prying them straight up from their sockets on the AirPort/Bluetooth card.

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Image 1/3: Push the cable slightly to the right. Image 2/3: Push the cable slightly to the right. Image 3/3: Push the cable slightly to the right.
  • 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.

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Image 1/1:
  • Peel off the tape covering the exhaust duct.

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Image 1/1: Two 6.2 mm screws
  • Remove the following T8 Torx screws securing the exhaust duct to the rear enclosure:

    • Two 6.2 mm screws

    • Two 4.7 mm screws

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Image 1/1:
  • Remove the four 7.3 mm T9 Torx screws securing the logic board to the rear enclosure.

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Image 1/2: Image 2/2:
  • Tilt the top of the logic board away from the rear enclosure.

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Image 1/3: Be careful not to snag the board on any of the rear enclosure's screw posts. Image 2/3: Be careful not to snag the board on any of the rear enclosure's screw posts. Image 3/3: Be careful not to snag the board on any of the rear enclosure's screw posts.
  • 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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Image 1/3: Gently push the battery away from the two plastic nubs. (This puts increased pressure on the spring contact at the other end.) Image 2/3: Once the battery's edge clears the two nubs, tilt it up out of its socket. Image 3/3: Once the battery's edge clears the two nubs, tilt it up out of its socket.
  • The PRAM battery is secured by a spring contact and two small plastic nubs.

  • Gently push the battery away from the two plastic nubs. (This puts increased pressure on the spring contact at the other end.)

  • Once the battery's edge clears the two nubs, tilt it up out of its socket.

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Image 1/1:
  • Remove the PRAM battery.

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Conclusion

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

Evan Noronha

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