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Introduction

Follow this guide to replace the PRAM battery in an iMac Intel 21.5" EMC 3068. The PRAM battery is located on the back side of the logic board, so replacing it requires completely 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.

  1. 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.
    • 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.

  2. 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.
    • 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.

  3. Continue running the tool up around the top left corner. Continue running the tool up around the top left corner. Continue running the tool up around the top left corner.
    • Continue running the tool up around the top left corner.

  4. Cut the adhesive along the top left of the display. Cut the adhesive along the top left of the display.
    • Cut the adhesive along the top left of the display.

  5. 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.
    • 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.

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

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

  8. 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.
    • 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.

  9. 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.
    • 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.

  10. 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".
    • 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".

  11. 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. 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.

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

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

  14. 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.
    • 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.

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

  16. Wedge the plastic card back into the top left corner. Wedge the plastic card back into the top left corner.
    • Wedge the plastic card back into the top left corner.

  17. 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.
    • 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.

  18. 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.
    • 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.

  19. 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.
    • 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.

  20. 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.
    • 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.

  21. If necessary, a plastic card can be used to cut any remaining sections of the bottom adhesive strip. If necessary, a plastic card can be used to cut any remaining sections of the bottom adhesive strip.
    • If necessary, a plastic card can be used to cut any remaining sections of the bottom adhesive strip.

  22. 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.
    • 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.

  23. Remove the following five Phillips  screws holding the lower support bracket in place: Four 3.2 mm screws
    • 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.

  24. Remove the lower support bracket (a.k.a. "chin strap") from the iMac enclosure.
    • Remove the lower support bracket (a.k.a. "chin strap") from the iMac enclosure.

  25. Remove the following T10 Torx screws securing the hard drive brackets to the iMac:
    • 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

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

  27. 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. 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.

  28. 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. 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.
    • 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.

  29. Remove the two 7.2 mm T8 Torx screws securing the power supply to the rear enclosure.
    • Remove the two 7.2 mm T8 Torx screws securing the power supply to the rear enclosure.

  30. 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 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.

  31. 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. 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.

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

  33. 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. 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.

  34. 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.
    • 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.

  35. 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.
    • 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.

  36. Remove the power supply from the iMac.
    • Remove the power supply from the iMac.

  37. Gently pull the fan cable connector straight out of its socket on the logic board. Gently pull the fan cable connector straight out of its socket on the logic board.
    • Gently pull the fan cable connector straight out of its socket on the logic board.

  38. Remove the three 10 mm T10 Torx screws securing the fan to the rear enclosure.
    • 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.

  39. Remove the fan from the iMac. Remove the fan from the iMac.
    • Remove the fan from the iMac.

  40. 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. 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.

  41. 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. 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.
    • 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.

  42. Remove the hard drive assembly from the iMac.
    • Remove the hard drive assembly from the iMac.

  43. Remove the 7.3 mm T8 Torx screw securing the hard drive tray to the rear enclosure.
    • Remove the 7.3 mm T8 Torx screw securing the hard drive tray to the rear enclosure.

  44. Remove the hard drive tray.
    • Remove the hard drive tray.

  45. Gently pull the left speaker cable straight out of its socket on the logic board. Gently pull the left speaker cable straight out of its socket on the logic board.
    • Gently pull the left speaker cable straight out of its socket on the logic board.

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

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

  48. Peel up the piece of tape connecting the left speaker connector to the SATA power and data cables. Peel up the piece of tape connecting the left speaker connector to the SATA power and data cables.
    • Peel up the piece of tape connecting the left speaker connector to the SATA power and data cables.

  49. 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.
    • 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.

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

  51. Disconnect all four antenna connectors by prying them straight up from their sockets on the AirPort/Bluetooth card. Disconnect all four antenna connectors by prying them straight up from their sockets on the AirPort/Bluetooth card. Disconnect all four antenna connectors by prying them straight up from their sockets on the AirPort/Bluetooth card.
    • Disconnect all four antenna connectors by prying them straight up from their sockets on the AirPort/Bluetooth card.

  52. Gently pull the right speaker cable connector parallel to the logic board, straight out of its socket on the logic board. Gently pull the right speaker cable connector parallel to the logic board, straight out of its socket on the logic board.
    • Gently pull the right speaker cable connector parallel to the logic board, straight out of its socket on the logic board.

  53. 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. 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.

  54. Peel off the tape covering the exhaust duct.
    • Peel off the tape covering the exhaust duct.

  55. Remove the following T8 Torx screws securing the exhaust duct to the rear enclosure:
    • Remove the following T8 Torx screws securing the exhaust duct to the rear enclosure:

    • Two 6.2 mm screws

    • Two 4.7 mm screws

  56. 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.
    • 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.

  57. Remove the four 7.3 mm T8 Torx screws securing the logic board to the rear enclosure.
    • Remove the four 7.3 mm T8 Torx screws securing the logic board to the rear enclosure.

  58. Tilt the top of the logic board away from the rear enclosure. When removing and installing the logic board, take care not to damage the delicate microphone ribbon cable at the bottom left. Lift the logic board straight up and out of the iMac.
    • Tilt the top of the logic board away from the rear enclosure.

    • When removing and installing the logic board, take care not to damage the delicate microphone ribbon cable at the bottom left.

    • 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.

  59. When reassembling your iMac, be sure 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 ensure the logic board is aligned correctly while you screw it in.
    • When reassembling your iMac, be sure 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 ensure the logic board is aligned correctly while you screw it in.

  60. Handling the board by the edges, flip the logic board over to access the PRAM battery. The PRAM battery is secured by a spring contact and two small plastic nubs. On the side between the two plastic nubs (opposite the spring contact), gently slide an opening pick in between the battery socket wall and the battery.
    • Handling the board by the edges, flip the logic board over to access the PRAM battery.

    • The PRAM battery is secured by a spring contact and two small plastic nubs.

    • On the side between the two plastic nubs (opposite the spring contact), gently slide an opening pick in between the battery socket wall and the battery.

    • Use the opening pick to slide the battery away from the two plastic nubs.

    • Once the battery's edge clears the two nubs, use the opening pick to tilt the battery up out of its socket.

  61. Remove the PRAM battery.
    • Remove the PRAM battery.

Conclusion

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

Adam O'Camb

Membre depuis le 11/04/2015

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