iMac Intel 27" EMC 2546 Logic Board Assembly Replacement

Step 1

Use the flat end of a spudger to disconnect each of the four antenna connectors from the AirPort/Bluetooth card.
Note the original positions for each connector when reconnecting the cables. From left to right on the card, the antennas are connected in the following order:
Leftmost
Top
Upper right
Lower right

My iMac has a slightly different assembly. There are 2 - T5 torx screws holding little clamps for each cable (2 clamps per screw). Certainly more secure but another size screw to deal with…

Greg Freeman - 12/11/17

My iMac also same with Greg mentioned. need to T5 torx driver. A1419. Late 2015, Korean Version.

Joseph Yang - 31/03/18

My 2017 has long WI-Fi card, It’s It’s a M.2, cuz no remove antenna. Undo WI-Fi card fix screws and pull out card. Easy one.

Tanya Chachanova - 24/11/18

Before I disconnect the cables, I use different color sharpies and draw a different color on each one’s head & then I take a picture of the cables connected to the board. Pic is my reference of which cable goes to what connector.

Macrepair SF - 10/11/19

I have a 2017 and I agree with Tanya. There are 2 T4 screws fastening the airport card to the motherboard. It’s easier to remove these and gently pull the airport card straight up out of the motherboard while leaving the 4 antenna wires fastened. You can’t see the connector or the airport card as it’s on the back side of the motherboard but just wiggle it side to side while pulling straight up and you’ll have no problem. I’ve broken off those tiny airport connectors in the past and it’s no fun replacing them.

Mike Jones - 10/02/20

same as Greg, did with the torx t5

Alejandro Piris Nino - 28/05/20

I have a 2019 iMac and we needed to use a T4 screw

Mike Manasewitsch - 11/09/20

My late 2015 has a Airport/Bluetooth card secured with two T5 screws. After removing them you can just wiggle and unplug it from the logic board, without needing to fiddle with the antenna connectors.

Robin Gottschalk - 29/01/21

Same as the other comments, in my iMac 27” retina 2015, the WiFi/Bluetooth board is a bit longer and the 4 coax cables are fixed by 2 T5 screws…

SURIN Dominique - 24/05/21

When reassembling a removed WiFi card keep 4 antenna leads attached as mentioned by poster (tanya et al) when reassembling as you replace logic board keeping it tilted forward helps in aligning the notch on card for easy reassembly and T3 screws replacingonce card is firmly seated.

robert -

When reassembling a removed WiFi card keep 4 antenna leads attached as mentioned by poster (tanya et al) when reassembling as you replace logic board keeping it tilted forward helps in aligning the notch on card for easy reassembly and T3 screws replacingonce card is firmly seated.

robert -

Can also confirm it for a Late 2015 iMac, there’s just 2 T3 screws to remove, simple move out the WiFi/Bluetooth board and let cable on place.

tomax -

Step 2

This is a delicate connection that can be easily broken.
Flip up the metal retaining bracket on the iSight camera cable.
Pull the camera cable connector straight out of its socket, toward the top of the iMac.

During disassembly, I taped the cable up and out of the way, as it tends to get in front of things.

Tony Ross - 16/10/16

I recall comments here about this being particularly sensitive. I had an issue with no iSight on rebuild, however taking to bits again and seating and reseating this connector a few times resulted in the iSight camera working again (phew).

Amuseme -

Step 3

Use the flat end of a spudger to disconnect the headphone jack cable connector from its socket on the logic board.
Gently push the cable out of the way.

On my 2017 iMac there is a tiny little cable and connector on the motherboard that is approximately half way along the motherboard and is connected down towards the base of the case. It came free easily when I removed my motherboard but just wanted to remind people to reconnect!

Stuart Swaffer - 28/11/19

It’s the microphone cable!

Koen van Eijk - 19/12/19

This pulls straight up, towards you.

Eric - 11/01/20

I broke mine…when inserted the speaker… How do I replace the headphone jack and cable?

mmx2000 - 15/06/20

Lift upwards with the spudger/fingernail, rocking it up back and forth.

(For those who have not seen this style of connector.)

Mike Rehbein - 12/04/21

+1 Missing the step on this 2019 iMac 27” guide to remove mic cable. It’s in other guides, just not here.

joe -

I cannot determine how to reconnect the headphone jack cable to the logic board. Are there better pictures anywhere that I could access?

Ron Owens -

Step 4

Remove the following screws from the front of the logic board:
Two 23.7 mm T10 screws
Four 7.4 mm T10 screws
One 20.8 mm T25 spacer screw
One captive T10 screw
This screw is beneath a hole in the logic board. You'll need a fixed screwdriver or the 60 mm extension from an iFixit driver kit to reach it.

The central screw is very difficult to reach! Use a long and very thin T10 screw driver

MrSchaeffer - 18/06/15

On my late 2015 there is another T10 (approx 16 mm long) on the lower edge slightly left of the hole in the logic board giving a total of 4 screws along the bottom edge.

Konrad Skeri Ekblad - 28/08/18

I’ve also found an extra T10 in my late 2015 iMac

luis - 20/11/18

My 2017 has small flat cable and connector on logic board. And all screws are changed to T 9

Tanya Chachanova - 24/11/18

Note: the T25 spacer is behind and to the left of the logic board and below the HDD bracket.

Tom - 23/12/18

My 2017 had all T8’s, including the captive screw beneath the motherboard

Mike Jones - 09/02/20

My 2017 had 4 T8 screws along the bottom of the logic board, not 3

greg - 17/03/20

Late 2015 iMac - mine had all T8 screws and 4 along the bottom row

Pete Mackenzie - 18/05/20

On 2019 iMac

Red = T8

Orange = T8

Green = T8

Yellow = T25

Mike Manasewitsch - 11/09/20

In 2017 too.

Andrew Gough - 16/03/21

2017 here.

IMPORTANT - note Tanya’s comment. The narrow flat cable in the middle - it’s the mic cable on a *tiny* ZIF. See iMac Intel 21.5" Retina 4K Display (2017) Logic Board Replacement

Also has the extra bolt middle lower edge.

All T8 except the yellow T25.

Andrew Gough - 16/03/21

In my iMac 27” retina 2015 all screws are T8.

There is also an another T8 screw between the left and central “orange” on bottom of the CPU board

SURIN Dominique - 24/05/21

Just completed and removed logic board. All my screws were T6. The screw beneath is a captive screw, stays retained in the fixture after unscrewing.

Keith Thomas -

If I change the logic card on an imac 27’ 2020, will the computer's memory be affected?

nizarishi -

There is a 25T stand off that is not listed. It is not on the board but beside or underneath the yellow/red on power supply side.

Tom Gordon -

Step 5

The hard drive SATA cable can't be removed just yet, but will get in the way of removing the logic board.
Pull the cable and connector through the right hard drive bracket. Move the cable to the right side of the iMac, out of the way of the exhaust port.

Anyone know if models that shipped with only a bladed SSD have the SATA cable still inside? I’m guessing probably not, but haven’t been able to confirm anywhere.

Jesse Mitchell - 22/11/18

The cable was so stiff, I didn’t try to pull it through the bracket. Instead I removed the upper screw holding the right HDD bracket in place. Then I rotated it counter clockwise enough to just move the cable behind it and out of the way. Once I did that, I screwed the bracket back into place. I reversed the process when I put the machine back together. It’s a Torx-10 BTW.

Kenneth Cluff - 28/03/19

Excellent tip, Kenneth! I did the same, made things easier.

Dave Hoppenrath - 07/11/19

Jesse, no SATA cable inside. My iMac came only with the blade SSD and an empty HDD bay, so I have to buy the SATA cable separately.

mveras1972 - 25/12/19

the card drive cable is affixed to the heat sink with some sort of adhesive. If it is not placed back similarly, the system cannot sense the heat sink temperature, and the fan will run at full speed continuously. I used double sided tape and pushed it back in adhered position after re-attaching logic board.

labah -

the above should read “the hard drive cable” , not card drive (typo)!

labah -

Step 6

Remove two 5.7 mm T10 screws from the top of the heat sink exhaust duct.

My model (2015) had another screw holding the heatsink duct and a stand-off holding the whole thing attached to the back. Even gently moving the logic board almost got the duct damaged till I realised what was going on so I’d suggest to be careful and DO NOT pull the logic board if it looks like it’s still attached - most likely it is!

Carlos Ferrari - 02/04/19

Carlos,

I am at a bit of a loss. I have a 2015 as well and removed everything else, but the motherboard is still not moving. I found the two, as shown in the picture, but can't find a third one anywhere on or around the heatsink duct. Any help is sincerely appreciated.

Marc

MarcW58 -

Ditto for the 2013 27”. One extra screw

Dave Sands - 30/12/19

My model 2546 late 2012 has 2 screws on heat sink shroud. First is on left side. The right can only be accessed with board tilted out a bit.

Michael Wright - 13/03/20

I just finished disassembling a late 2017 27” Retina and for the life of me I couldn’t get the logic board to come out. What. I discovered was that there is a part of the heat sink shroud that is held in place by a stand off boss for the power supply. You will need to remove the stand off boss using a T25. Remove carefully and save for reassembly…

David Brix -

Same here for late 2014.

Jamuel Starkey -

Yes, there is a screw holding down the fan shroud it is an angled black part where the guy's left hand index finger is located in Step 56

Carl Schultz -

Step 7

Tilt the logic board slightly forward.
Lift the logic board straight up and out of the iMac. Be careful not to snag on any of the screw posts attached to the inside of the rear case.

You should add a step about removing the sata cable here. When following the directions in reverse I forgot to put in back on and had to remove the motherboard again.

Ken Prows - 21/06/19

If you are having a hard time removing it, you might have forgot to remove the spacer rod when you removed all the motherboard screws. In my case, it was a T20.

Eric - 11/01/20

The 2017 iMac has a small cable with a ZIF connector coming from the bottom of the machine that needs to be detached from the logic board before it can be removed.

greg - 17/03/20

I can confirm this. As i recognized the cable after i removed the logic board i had some trouble to find the spot where to plug it in.

sebastian.wittl - 07/03/21

If you are having a hard time removing it, you might have forgot to remove the spacer rod when you removed all the motherboard screws. In my case, it was a T20. This is in my late 2015 the case. Just like Eric said 11-01-2020.

John - 08/01/21

Same for late 2012. For those curious the spacer is just to the left and appears to attach to the heat sink.

skiingjoo - 21/01/21

The iMac 27” didn’t come with the PCIe SSD card so of course there wasn’t the necessary screw to mount one.

Here is the screw to order;

https://www.ebay.com/itm/283482947478?ch...

What I did was find a screw that fit. Happened to be the case screw from the iFixit external 2.5” case but since that was a countersunk screw, I fabricated a washer for it.

Mike Rehbein - 13/04/21

Step 8

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.
You can use a USB flashdrive or ethernet cable to ensure the logic board is seated correctly while you screw it in.

To help me line up the IO ports, I filled all the USB ports on the back with thumb drives before I screwed the Logic board back down. Worked like a charm!

Alex Grayson - 14/03/18

Ugh! Wish I saw this before. I did this mod and failed to do this step and now only one Thunderbolt 3 port works at a time and the SD card has to get pushed way further to get it to read. I hate taking this thing apart!

scolvin - 14/08/20

Thanks Alex :)

Mike Rehbein - 13/04/21

iMac (Retina 5K, 27-inch, 2017) の場合、Thunderbolt 3（USB-C）ポートの位置がシビアです。

Ethernet、USB 3ポート、Thunderbolt 3（USB-C）へ最低でも各１本（合計３本）を差し込んだままの状態でロジックボードのネジを閉めるようにすることを強くおすすめします。

EthernetケーブルとUSBメモリの２本を挿して調整し組み上げましたが、最終的にThunderbolt 3（USB-C）が刺さらないことが後で判明し、結果組み直しをしなくてはいけませんでした。

For iMac (Retina 5K, 27-inch, 2017), the location of the Thunderbolt 3 (USB-C) port is severe.

It is highly recommended to close the logic board screws with at least one cable each (total of three) plugged into the Ethernet, USB 3 port, and Thunderbolt 3 (USB-C).

I plugged in two Ethernet cables and a USB memory stick, adjusted and assembled the board, but in the end I found out later that the Thunderbolt 3 (USB-C) would not stick, so I had to reassemble the board.

Translated with www.DeepL.com/Translator (free version)

JapanWolf -

貴重な情報ありがとうございました！

Midori Doi -

I do this job fairly frequently and I have a small box in my iMac tool kit containing a headphone jack, four USB drives, a short two-ended Thunderbolt cable and the end of a red moulded Ethernet cable to keep things aligned from the back when screwing the logic board back into place.

I loosely screw all the screws in, then tighten them gradually, going round the board several times to make sure it lands in exactly the right position.

John Blagden -

iMac Intel 27" EMC 2546 Logic Board Assembly Replacement

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