Apple iMac (27-inch, Mid 2011) Repair

 Apple Technician Guide

iMac (27-inch, Mid 2011)

Updated: 2011-08-29

 Apple Inc.

© 2011 Apple Inc. All rights reserved.

Under the copyright laws, this document may not be copied, in whole or in part, without the
written consent of Apple.

Every eort has been made to ensure that the information in this document is accurate. Apple
is not responsible for printing or clerical errors.

Apple
1 Innite Loop
Cupertino, CA 95014-2084
USA
+ 1 408 996 1010
www.apple.com

Apple, the Apple logo, Mac, and Macintosh are trademarks of Apple Inc., registered in the U.S.
and other countries.

iMac (27-inch, Mid 2011)

Contents

About This Guide

Updates 11

Updated 29 August 2011 11
Updated 22 July 2011 11
Updated 28 June 2011 11
Updated 16 June 2011 11
Updated 15 June 2011 12
Updated 10 June 2011 12
Introduced 04 May 2011 12

Feedback 12

Basics

Overview 14

Identifying Features 15
Product Congurations 15

Thunderbolt 16

Safety Precautions 17

Serial Number Location 18

Troubleshooting

General Troubleshooting 20

Update Software & Firmware 20
Wireless Troubleshooting 20
Troubleshooting Theory 20
Hardware vs. Software 20
Common Reset Procedures 21

Power On Self Test (POST) 21
Starting Up in Safe Mode 21
Resetting the System Management Controller (SMC) 22
Resetting Parameter RAM (PRAM) 22
Coin Battery Removal, Testing, and PRAM Reset 23
Recovering a Lost Firmware Password 23

Diagnostics 24
Sensor Errors 24
Sensor and Fan Connector Locations 27
Sensors on Front of Logic Board 27
Sensors on Back of Logic Board 28
Diagnostic LEDs 28
LED Functions 29

LED Startup Sequence 30

Block Diagram 31
Functional Overview: Front of Logic Board 32
Functional Overview: Back of Logic Board 33

Symptom Charts 34

Startup and Power 34

No Power 34
No Startup 36
Intermittent Shutdown 38
Kernel Panic / System Crashes 43
No Video 45
Corrupted Video 47
Burnt Smell/Odor 50
Uncategorized Symptoms 51

Display 52

Backlight Issue/No Backlight 52
Noise / Unstable Flickering 54
Incorrect/Missing Colors 58
Distorted/Blurred Image 59
Pixel Anomalies 61
Vertical/Horizontal Lines 62
Non-Uniform Brightness / Color 64
Cosmetic Issues 65
Uncategorized Symptoms 65

Mass Storage 66

Hard Drive or SSD Not Recognized 66
Hard Drive Read/Write Errors 68
Hard Drive Noisy 70
Optical Drive Not Recognized 72
Optical Drive Rejects or Does Not Accept Media 74
Optical Drive Read/Write Error 76
Optical Drive Not Performing to Specications 78
Optical Drive Noisy 80
SD Memory Card Cannot Be Inserted Into Slot 82
SD Memory Card Not Recognized 83
Uncategorized Symptoms 84

Communications 85

AirPort Issues 85
Deep Dive 87
Bluetooth Issues 88

AirPort Card Kernel Panic 90
Ethernet Issues 91
Wireless Input Device Does Not Pair 93
Uncategorized Symptoms 95

Input/Output Devices 96

Thunderbolt Not Recognized 96
Thunderbolt Target Disk Mode Issues 97
Thunderbolt Target Display Mode Issues 100
Apple Remote Issues 104
Distorted Audio From Internal Speaker(s) 108
No Audio From Internal Speaker(s) 109
Camera Issues 111
USB Port Not Recognized 114
Wired Keyboard Does Not Work Properly 116
Keyboard: Specic Keys Do Not Respond 118
Wired Keyboard/Mouse Not Recognized 118
Wireless Input Device Does Not Pair 120
Apple Wireless Mouse/Magic Trackpad Erratic Tracking 122
Wireless Input Device Loses Connection 123
Apple Battery Charger Does Not Charge Batteries 125
Deep Dive
Uncategorized Symptoms 125

Mechanical 127

Noise/Hum/Vibration 127
Fan Failures / Thermal Issues 130
Stand/Hinge Issues 132
Uncategorized Symptoms 132

Take Apart

General Information 134

Opening the Unit 134
Required Tools 134
Required Special Tools for Glass Panel 135
Cleaning Tools Starter Kit 135
Cleaning & Handling the Glass Panel 136
Do’s and Don’ts 136
Handling a Broken Glass Panel 137
How to Remove a Broken Glass Panel 137
Safety 142
EMI Tape 143
Logic Board Handling 144
Reassembly Steps 144
Note About Images in This Manual 144
Screw Sizes 144

Access Door 145

Memory 147

Removal 148

Reassembly 149

Glass Panel 150

Removal 151
Reassembly 152

EMI Tape 155

LCD Panel 156

Removal 157
Handling the Panel 162
Reassembly 163

Battery 167

Removal 168
Reassembly 168

Camera 170

Removal 171
Reassembly 172

Vertical Sync Cable (Vsync)/Temp Sensor 173

Removal 174
Reassembly 176

DisplayPort Cable 178

Removal 179
Reassembly 180

DisplayPort Power Cable 182

Removal 183
Reassembly 183

AirPort Antenna, Left 185

Removal 186
Reassembly 187

AirPort Antenna, Right 188

Removal 189
Reassembly 190

Audio Ports and Cable 191

Removal 192
Reassembly 193

AirPort Card 194

Removal 195
Reassembly 196

Bluetooth Antenna 197

Removal 198
Reassembly 198

Bluetooth Board 199

Removal 200
Reassembly 200

LED Backlight Board 201

Reassembly 203

Power Supply 204

Removal 205
Reassembly 206

Backlight Pressure Wall 207

Removal 208
Reassembly 208

Power Supply/Hard Drive Pressure Wall 209

Removal 210
Reassembly 210

Hard Drive 212

Removal 213
Reassembly 213
Reinstalling Software That Came with the Computer 214

Optical Drive 215

Removal 216
Reassembly 217

Optical Drive Data Cable 219

Removal 220
Reassembly 221

Optical Drive Sensor Cable 222

Solid State Drive (SSD) 224

Removal 225
Reassembly 226
Reinstalling Software That Came with the Computer 226

Optical Drive Fan 229

Removal 230
Reassembly 230

SD Card Reader 231

Removal 232
Reassembly 232

SD Card Reader Cable 233

Removal 234
Reassembly 234

IR Board and Cable 235

Removal 236
Reassembly 237

Logic Board 238

Removal 239
Handling the Logic Board 242
Reassembly 243

SSD Data Cable 249

Removal 250
Reassembly 251

Video Card 252

Removal 253
Reassembly 254

Optical/MXM Pressure Wall 255

Removal 256
Reassembly 256

Hard Drive Data Cable 257

Removal 258
Reassembly 259

Hard Drive Power Cable 260

Removal 261
Reassembly 262

Right Speaker 263

Removal 264
Reassembly 265

CPU Fan 266

Removal 267
Reassembly 268

Ambient Temp Sensor 270

Removal 271
Reassembly 272

Left Speaker 273

Removal 274
Reassembly 275

Hard Drive Fan 277

Removal 278
Reassembly 278

Mechanism Cover 279

Removal 280
Reassembly 281

Stand 282

Removal 283
Reassembly 284

Mechanism 286

Removal 287
Reassembly 287

Bluetooth/Camera/Sensor Cable 288

Removal 289
Reassembly 291

DC Power Cable 294

Removal 295
Reassembly 295

Rear Housing 296

Reassembly 297

Additional Procedures

Retrieving Mechanism 300

Views

Exploded Views 305

Exploded View #1 305
Exploded View #2 306
Exploded View #3 307

External Views 308

Rear View 308
Ports 309

Internal Views 310

Components Below LCD 310
Components Below Logic Board 311
Logic Board, Front Side 312
Logic Board, Back Side 313

Screw Chart 314

 Apple Technician Guide

About This Guide

iMac (27-inch, Mid 2011)

© 2011 Apple Inc. All rights reserved.

Updates

Updated 29 August 2011

Take Apart:

• Hard Drive: Corrected screw pin 922-7001 to be T8 rather than T10.

Views:

• Exploded View: Updated “Pressure Wall, Optical” part number to 922-9926.

• Screw Chart: Corrected screw pin 922-7001 to be T8 rather than T10.

Updated 22 July 2011

Basics:

• Thunderbolt: Added links to Apple Support articles:

• HT4644: Getting the best performance from Thunderbolt

• HT4614: About Thunderbolt to Thunderbolt cable (2 m)

• HT4617: Using Thunderbolt with Boot Camp and Windows 7

Troubleshooting:

• Revised instructions for Resetting the System Management Controller (SMC).

• Updated references to “System Proler” to be “System Information (System Proler in Snow
Leopard)”.

Take Apart:

• Hard Drive & Solid State Drive: Updated “Reinstalling Software” section to include
information about both Mac OS X 10.6 Snow Leopard and OS X 10.7 Lion.

Updated 28 June 2011

Troubleshooting:

• Input/Output: Added sections for Thunderbolt Not Recognized, Thunderbolt Target Disk
Mode Issues, and Thunderbolt Target Display Mode Issues.

Updated 16 June 2011

Take Apart:

• Memory: Added guide to identify physical RAM slots from information found in System
Proler and diagnostics.

2011-08-29

iMac (27-inch, Mid 2011) About This Guide — Updates 11

Updated 15 June 2011

Take Apart:

• Added chapters for Solid State Drive and Solid State Data Cable.

Views:

• Exploded Views: Added Solid State Drive, brackets, and Solid State Data Cable.

• Added CTO rear cover, 922-9925.

Screw Chart:

• Added SSD bracket screw, 922-9927.

Updated 10 June 2011

Take Apart:

• LCD Panel: Added note to reassembly step 5, “Important: If the display power connector is
not rmly or completely seated, it could cause a No Video symptom.”

Introduced 04 May 2011

Feedback

We want your feedback to help improve this and future Technician Guides!
Please email any comments to [e-mail]

2011-08-29

iMac (27-inch, Mid 2011) About This Guide — Feedback 12

 Apple Technician Guide

Basics

iMac (27-inch, Mid 2011)

© 2011 Apple Inc. All rights reserved.

Overview

2011-08-29

The iMac (27-inch, Mid 2011) has an all-aluminum enclosure with a glass front which extends
all the way to the top, left and right edges. Its external appearance is nearly identical to the
previous two models, iMac (27-inch, Late 2009) and iMac (27-inch, Mid 2010), but includes new
features such as Thunderbolt, and a FaceTime HD camera.

The Mid 2011 model can be most easily distinguished from the Late 2009 and Mid 2010 models
by the two Thunderbolt ports on the rear, and the location of the battery on the front of the
logic board.

iMac (27-inch, Mid 2011) Basics — Overview 14

Identifying Features

The iMac (27-inch, Mid 2011) computer features include:

• 27-inch (viewable) LED-backlit glossy widescreen TFT display with support for millions of
colors; 2560 by 1440 pixel resolution

• Processor and memory:

• 2.5GHz quad-core Intel Core i5 with 6MB on-chip shared L3 cache

• 3.1GHz quad-core Intel Core i5 with 6MB on-chip shared L3 cache

• 3.4GHz quad-core Intel Core i7 (CTO)

• 4GB (two 2GB SO-DIMMs) of 1333MHz DDR3 SDRAM; four SO-DIMM slots support up
to 16GB maximum

• Graphics and video support:

• AMD Radeon HD 6770M with 512MB of GDDR5 memory

• AMD Radeon HD 6970M with 1GB of GDDR5 memory

• AMD Radeon HD 6970M with 2GB of GDDR5 memory

• Two Thunderbolt ports, Mini DisplayPort output with support for DVI, VGA, and dual-link DVI
(adapters sold separately), four USB 2.0 ports, one FireWire 800 port, Gigabit Ethernet

• Built-in FaceTime HD 720p camera

• Hard Drive: 1TB or 2TB 7200-rpm Serial ATA

• Solid State Drive options (CTO):

• 256GB SSD (SSD only, without a hard drive)

• 256GB SSD + 1TB Serial ATA Hard Drive

• 256GB SSD + 2TB Serial ATA Hard Drive

• SDXC (Secure Digital Extended Capacity) card slot; supports higher card capacity, 32GB-2TB

• Ships with and requires at least Mac OS 10.6.6

2011-08-29

Product Congurations

For product congurations, refer to AppleCare Tech Specs: http://support.apple.com/specs/

iMac (27-inch, Mid 2011) Basics — Overview 15

Thunderbolt

Thunderbolt is a revolutionary I/O technology that supports high-resolution displays and high­performance data devices through a single, compact port. It sets new standards for speed,
exibility, and simplicity. Read more at http://www.apple.com/thunderbolt/

Important: Thunderbolt requires up-to-date software and rmware to function properly. Obtain
the latest updates via Software Update.

Caution: The Thunderbolt ports are keyed for cable insertion in only one direction. Be sure to
insert cables with the correct orientation. Do not use excessive force if the cable does not t.

Reassembly Note: The Thunderbolt port has a precise t. To properly align logic board with rear
housing, you MUST plug in Thunderbolt or Mini DisplayPort cables to both Thunderbolt ports and
also to the furthest left USB port while tightening screws.

2011-08-29

For more information, see the following Apple Support articles:

• HT4644: Getting the best performance from Thunderbolt

• HT4614: About Thunderbolt to Thunderbolt cable (2 m)

• HT4617: Using Thunderbolt with Boot Camp and Windows 7

iMac (27-inch, Mid 2011) Basics — Thunderbolt 16

Safety Precautions

Warning: HIGH VOLTAGE: The power supply and LED backlight board remain powered up

whenever the computer is plugged in, whether or not the computer has been turned on.
Use extreme caution when troubleshooting with the glass panel removed.

• Don’t work alone. In the event of electrical shock it is important to have another
individual present who can provide assistance.

• Keep one hand in your pocket when working on any iMac computer that is
plugged in. This will help ensure that your body does not provide a path to
ground in the event that you accidentally make contact with line voltage.

• Don’t wear jewelry, watches, necklaces, or other metallic articles that could
present a risk if they accidentally make contact with power supply circuitry.

Important: If computer is shut down by removing the power cord, allow power supply and

LED backlight board capacitors a good 2-3 minutes to discharge before handling. However, if
you select “Shut Down” via the Apple menu, the computer will discharge the capacitors almost
immediately.

2011-08-29

iMac (27-inch, Mid 2011) Basics — Safety Precautions 17

Serial Number Location

The iMac (27-inch, Mid 2011)’s serial number is located on the bottom of the stand. When
replacing a stand, use a ne-tip black permanent marker to neatly write the serial number on
the bottom of the new stand.

2011-08-29

iMac (27-inch, Mid 2011) Basics — Serial Number Location 18

 Apple Technician Guide

Troubleshooting

iMac (27-inch, Mid 2011)

© 2011 Apple Inc. All rights reserved.

General Troubleshooting

Update Software & Firmware

Important: Before you begin troubleshooting, ensure the correct version of OS X is installed,

and check for and apply the latest software and rmware updates.

Firmware is the name given to software that is written into memory circuits such as ash
memory, that will hold the software code indenitely, even when power is removed from
the hardware. Firmware on Intel Mac computers is designed to be updated if necessary by
running the OS X Software Update check (available in the Apple () menu) while the computer
is connected to the Internet. For more information about rmware updates, refer to Apple
Support article HT1557: About rmware updates for Intel-based Macs.

Wireless Troubleshooting

For Bluetooth and wireless connectivity issues, refer to the following Apple Support articles:

• TS3048: Troubleshooting wireless mouse and keyboard issues

• HT3887: Wireless input devices: Bluetooth frequently asked questions

• HT1365: AirPort and Bluetooth: Potential sources of wireless interference

• HT3903: Apple Wireless Keyboard, Mouse, and Trackpad: How to install batteries

• Bluetooth Service Diagnostic (BSD) self-paced training

• Bluetooth Troubleshooting Course

2011-08-29

Troubleshooting Theory

For general information on troubleshooting theory, go to GSX and nd the Service Training
course menu link. From there you can access the Troubleshooting Theory self-paced course.

Hardware vs. Software

For information on how to isolate a hardware issue from a software issue, refer to Apple
Support article TS1388: Isolating issues in OS X

For information on how to troubleshoot a software issue, refer to the following Apple Support
articles:

HT1199: OS X: How to troubleshoot a software issue
TS1394: Troubleshooting OS X installation and software updates (OS X v10.6 and earlier)
HT2956: Troubleshooting OS X installation from CD or DVD

iMac (27-inch, Mid 2011) General Troubleshooting 20

Common Reset Procedures

Power On Self Test (POST)

Intel-based Mac computers such as the iMac rely on a combination of tones and blinking LEDs
to display Power On Self Test (POST) error codes.

• If the computer detects out-of-specication or no SDRAM, the screen will remain black
but the computer will beep. This error condition may be due to physically damaged RAM,
installing an incorrect type of RAM, or not having RAM installed.

• Some RAM may appear to pass the Power-On-Self-Test (POST) but still cannot be used by
the operating system. In this case, the computer will display a gray screen, sound three
tones and repeat tones until computer is turned o.

• The solution to both of these situations is to rst re-seat memory and test computer again.
If memory fails POST again, remove all installed memory and test by installing one by one
each memory module that has been veried to work correctly on another computer (i.e.,
“known-good” memory) or order new memory.

• A sequence of tones heard at startup or a no video symptom may also be xed by
temporarily removing/replacing the backup battery.

For more information, refer to Apple Support article

HT2538: iMac (Mid 2007) and later models: About startup tones

Starting Up in Safe Mode

A Safe Boot is a special way to start OS X when troubleshooting. Starting up into Safe Mode
does several things that can help resolve software or directory issues that may exist on the
startup volume. To start up in Safe Mode:

1. Make sure computer is shut down.

2. Press power button.

3. Immediately after you hear the startup tone, press and hold Shift key.
Note: The Shift key should be held as soon as possible after startup tone but not before.

4. Release Shift key when you see the screen with the gray Apple and progress indicator

(looks like a spinning gear). Note that booting into Safe Mode will take longer than a normal
startup. During startup, the words ”Safe Boot” appear on the OS X startup screen and a gray
progress bar is displayed on bottom of window (since OS X 10.6).

5. To leave Safe Mode, restart computer normally, without holding down any keys during
startup.

For more information, refer to the following Apple Support articles:

HT1564: OS X: What is Safe Boot, Safe Mode?
TS1884: Safe Boot takes longer than normal startup

2011-08-29

iMac (27-inch, Mid 2011) General Troubleshooting 21

Resetting the System Management Controller (SMC)

The System Management Controller (SMC) is a chip on logic board that controls all power
functions. If computer is experiencing any power issue, such as not starting up, not displaying
video, sleep issues, or fan noise issues, resetting SMC may resolve it. To reset SMC on an
iMac (27-inch, Mid 2011):

1. From the Apple () menu, choose Shut Down (or if the computer is not responding, hold
power button for approximately ten seconds until it powers o).

2. Unplug the computer’s power cord.

3. Wait 15 seconds.

4. Attach the computer’s power cord, making sure power button is not being pressed.
Note: If you press the power button while inserting the power cord, the iMac will enter

a mode in which the fans run at full speed. For more information, refer to Apple Support
article TS1433: iMac: Fans run at full speed after computer turns on

5. Wait 5 seconds, then press the power button to turn on the computer.

For more information, refer to Apple Support article

HT3964: Intel-based Macs: Resetting the System Management Controller (SMC)

Resetting Parameter RAM (PRAM)

PRAM stores certain system and device settings in a location that OS X can access quickly.
Exactly which settings are stored in the computer’s PRAM varies depending on the type of
computer as well as the types of devices and drives connected. To reset PRAM:

1. Shut down the computer.

2. Locate the following keys on keyboard: Command, Option (Alt), P, and R. You will need to

hold these keys down simultaneously in Step 4.

3. Press power button.

4. Immediately press and hold Command-Option-P-R keys.
Important: You must press this key combination before the gray screen appears.

5. Hold down keys until the computer restarts, and you hear the startup chime a second time.

6. Release keys.

For more information, refer to the following Apple Support articles:

HT1242: OS X: What’s stored in PRAM
HT1379: Resetting your Mac’s PRAM and NVRAM

2011-08-29

iMac (27-inch, Mid 2011) General Troubleshooting 22

Coin Battery Removal, Testing, and PRAM Reset

1. Shut down and unplug the computer. Allow several minutes for power supply to discharge.

2. The coin battery is located on the front side of the logic board (see graphic below) and

provides power for the battery-backed RAM and clock. In order to reset the PRAM remove
the coin battery for 1-2 minutes.

2011-08-29

3. Measure DC voltage on battery touching battery with red probe, and grounding with black
probe. If voltage is 2.7v or less, replace battery.

4. Reinstall battery and reassemble computer.

5. Power on computer.

6. If computer starts up successfully, check for and apply the latest software and rmware

updates.

Recovering a Lost Firmware Password

Only Apple Retail Stores or Apple Authorized Service Providers can unlock an
iMac (27-inch, Mid 2011) protected by a rmware password.

Refer to Apple Support article TS3554: Recovering a lost rmware password.

iMac (27-inch, Mid 2011) General Troubleshooting 23

Diagnostics

The following diagnostics are required for this product:

• Apple Service Diagnostic (ASD), version 3S145

• Apple Hardware Test (AHT), version 3A213

Note: Install DVD silkscreen reads AHT version 3A214.

Note: Follow instructions in “Read Me” le that accompanies any diagnostic. Failure to run

diagnostics as instructed can lead to false error codes.

Sensor Errors

Run latest available service utilities to determine if any thermal sensors or fans are
malfunctioning. When a test reports an error, reseat appropriate connections and check that
all air ows are free from obstruction. If issue persists, replace the corresponding part (sensor,
fan, logic board, video card, or power supply). See chart below for correlation between aected
sensor, sensor location, and additional checks to perform.

Note: AHT can be run by pressing the D key on startup (if hard drive was not reformatted, or if
adequate system specic restore DVD is inserted). If a sensor error is detected, AHT will report
an error code containing the aected sensor name (ex: “4SNS/1/40000000 TC0H” error code
reports to sensor TC0H).

Sensor Suspected part and Location Suggested Action Notes

TA0p Excessive incoming ambient

air temperature, or ambient
temp sensor (part of CPU
fan assembly) is damaged/
disconnected from logic
board.

T00p Connector J5510. Excessive

optical drive area temperature,
or ODD temp sensor
damaged/ disconnected from
logic board.

Tm0p Excessive logic board

temperature (this sensor is
part of logic board)

TL0p Excessive LCD panel area

temperature.l

Verify that incoming/outgoing
air vents are free from
obstruction , that ambient
sensorcable is securely
connected to the left edge of
the logic board. Replace fan
sensor if damaged.

Verify sensor cable is securely
connected to the logic
board and the sensor is
properly attached to the ODD
mechanism. Replace sensor
cable if damaged.

Test with known-good logic
board

Verify that the DisplayPort
cable is securely connected to
the LCD panel and connector
J9002 on the logic board.

All fans ramp
at full speed if
fan/sensor is
disconnected.

The ODD fan
will run at full
speed if sensor
is disconnected.

The CPU fan will
run at full speed
if the sensor is
disconnected.

2011-08-29

iMac (27-inch, Mid 2011) General Troubleshooting 24

TS2p Excessive upper internal

enclosure temperature, or
Bluetooth/camera/sensor
damaged/disconnected from
top of logic board.

TS0P Excessive upper internal

enclosure temperature, or
sensor damaged/disconnected
from top of logic board.

Verify that the Bluetooth/
camera/sensor cable is
securely connected to the top
of the logic board. Replace the
cable if damaged.

Verify that the ‘Temp R’ sensor
cable is securely connected
to the top of the logic board.
Replace the cable if damaged.

Left skin temp
sensor

Right skin temp
sensor

TC0H Excessive processor heat sink

temperature, or CPU temp
sensor damaged/disconnected
from logic board (this sensor is
part of logic board)

TC0p Excessive logic board

temperature (this sensor is
part of logic board)

TC0c Excessive logic board

temperature (this sensor is
part of logic board)

TC1c Excessive logic board

temperature (this sensor is
part of logic board)

TC2c Excessive logic board

temperature (this sensor is
part of logic board)

TC3c Excessive logic board

temperature (this sensor is
part of logic board)

TCGc Excessive logic board

temperature (this sensor is
part of logic board)

TCSc Excessive logic board

temperature (this sensor is
part of logic board)

TCXc Excessive logic board

temperature (this sensor is
part of logic board)

TG0D Excessive graphics processor

die temperature (sensor is part
of graphics processor chip)

Check CPU sensor cable
connection to logic board. It
is located on back side and
requires removal of the logic
board.

Test with known-good logic
board

Test with known-good logic
board

Test with known-good logic
board

Test with known-good logic
board

Test with known-good logic
board

Test with known-good logic
board

Test with known-good logic
board

Test with known-good logic
board

Test with known-good video
card

If the sensor is
disconnected,
the CPU fan
will run at full
speed.

(TG0D) -- GPU
Die Digital

2011-08-29

iMac (27-inch, Mid 2011) General Troubleshooting 25

TG0H Excessive graphics processor

heat sink temperature, or
GPU temp sensor damaged/
disconnected from back side
of logic board (this sensor is
part of video card assembly)

TH0O Excessive hard drive area

temperature (sensor is part of
HDD)

Tp1P,
Tp2H,
Tp3H

Excessive power supply
temperature (these sensors
are part of the power supply)

ODD fan Optical fan located next to

right speaker

HDD fan Hard drive fan, located below

logic board, near hard drive

CPU fan CPU fan, located next to left

speaker.

Check GPU sensor cable
connection to logic board.
(requires removal of the logic
board to access).

Verify HD power cable
is securely connected to
logic board, and is correctly
connected and oriented to
the hard drive end. Check for
damaged cable or logic board.

Test with known-good power
cable harness , or known­good power supply board.

Verify that the ODD fan
cable is securely connected
to the right side of the logic
board and that there are
no obstructions that would
prevent the fan from rotating.
Replace fan if error continues.

Verify that the HDD fan cable
is securely connected to the
top of the logic board and
that there are no obstructions
that would prevent the fan
from rotating. Replace fan if
the error continues.

Verify that CPU fan/ambient
sensor cable is securely
connected to the left side
of the logic board and that
there are no obstructions that
would prevent the fan from
rotating. Replace fan if the
error persists.

If sensor is
disconnected
the ODD fan
will run at full
speed.

The HD fan
may run at full
speed if the HD
power cable is
disconnected/
misconnected.

Normal fan
operation,
except the ODD
fan

Normal fan
operation,
except the HDD
fan

Normal fan
operation,
except the CPU
fan

2011-08-29

iMac (27-inch, Mid 2011) General Troubleshooting 26

Sensor and Fan Connector Locations

Thermal sensors and fan connector locations are shown below. Ensure cables are correctly
routed and the sensors and fans are properly connected. If a sensor or fan is faulty or not
connected, diagnostics (AHT, ASD, MRI) will generate an error code.

Sensors on Front of Logic Board

(A) Right skin temp sensor

(B) HDD fan

(C) Bluetooth/camera/temp sensor

(D) ODD fan

(E) ODD temp sensor

(F) IR

(G) Ambient temp sensor

(H) CPU fan

2011-08-29

iMac (27-inch, Mid 2011) General Troubleshooting 27

Sensors on Back of Logic Board

(A) Video card sensor

(B) CPU sensor

Diagnostic LEDs

The iMac (27-inch, Mid 2011) computer has four built-in diagnostic LEDs on the main logic
board that can help you to troubleshoot the computer. The LEDs are located above the speaker
connectors and slightly to the left. Refer to the next page for a close up graphic of the
troubleshooting LEDs.

2011-08-29

iMac (27-inch, Mid 2011) General Troubleshooting 28

LED Functions

LED #1

• Indicates that the trickle voltage from power supply has been detected by main logic board.
This LED will turn ON when you connect the iMac to a working AC power source. The LED
will remain ON as long as the computer is ON or asleep.

• When computer has been correctly shutdown, the LED#1 behavior may dier:

• - If a startup event is scheduled in System Preferences/Energy saver, LED#1 will stay ON after
a correct shutdown,

• - If no startup event is scheduled in System Preferences/Energy saver, LED#1 will turn OFF
and will stay OFF as long as power cord is kept connected and AC power source is present.
Disconnecting the power cord and plugging it back will turn back this LED ON , even if
computer is still o.

• After disconnecting and reconnecting the AC power source, this LED could remain OFF if
the AC power source is missing or disconnected , if the logic board is disconnected from the
power supply or from the AC receptacle, or if the power supply board is faulty.

2011-08-29

LED #2

• Indicates that computer is turned on. This LED will be ON as long as computer is turned on
(but is not asleep) and power supply and voltage regulators are working correctly.

LED #3

• Indicates that computer and video card are communicating. This LED will be ON when
computer is communicating properly with video card. If LEDs 1 and 2 are ON and you heard
the startup sound, but LED 3 is OFF, then the backup battery (on back of logic board) may
need to be reseated, or the video card might be installed incorrectly or needs replacement.

LED #4

• Indicates that computer and LCD panel are communicating. This LED will be ON when
computer is turned on and video signal is being generated. If LED#4 is ON and there is no
image on display, then the LCD panel, the LED backlight board, or the cables between LCD
and logic board or backlight board might be installed incorrectly, or need replacement.

iMac (27-inch, Mid 2011) General Troubleshooting 29

LED Startup Sequence

LED #1 = Power available.

If no LED is visible:

• First disconnect the power cord from computer, then reconnect it to reset the LED
status, in case computer was correctly shutdown and AC was kept connected since

• Verify AC source

• Verify known-good power cord is connected

• Verify cable connection between AC inlet and power supply

• Verify cable connection between power supply and logic board

• Verify power supply

LED #1 + LED #2 = Power available, and system is powered on.

If second LED is not visible when power button is pressed:

• Verify power button connection to logic board

• Verify power button functionality

• Verify cable connection between power supply and logic board

• Verify power supply

• Verify logic board

LED #1 + LED #2 + LED #3 = Power available, system is powered on, and video card found.

If third LED is not visible after power on:

• Verify that the MXM video card is seated properly

• Verify if boot chime is present and fans are running when powered ON (reset SMC and
PRAM, reseat or check backup battery if necessary for proper boot up):
If POST boot chime is not heard, go to No Startup symptom ow,
If POST boot chime is heard, go to No Video symptom ow.

LED #1 + LED #2 + LED #3 + LED #4 = Power available, system is powered on, video card
found, and internal LCD found.

If fourth LED is not visible after power on:

• Verify internal DisplayPort cable connections between LCD panel and logic board

• Inspect LCD display cables for cable damage

• Verify external video functionality, and according to result check the following items:
If external display works then verify/replace the LED backlight board
If external display works then verify/replace the LCD panel
If external display does not work verify/replace the logic board

2011-08-29

iMac (27-inch, Mid 2011) General Troubleshooting 30

Block Diagram

iMac (27-inch, Early 2011) System Block Diagram

Refer to this diagram to see how modules are interrelated.

AC Inlet

Optical Drive

Temperature

Sensor

Backlight

Controller

Hard Drive

Display
Temperature

Sensor

Skin

Temperature

Sensor

SD Card

Reader

Microphone

SSD (CTO)

MXM

Temperature

Sensor

MLB

Bluetooth

Antenna

Camera,

ALS

SO-DIMM

SO-DIMM

SO-DIMM

SO-DIMM

AC/DC

Temperature

Sensor

IR Sensor

Fan

Fan

Fan

Power
Button

2011-08-29

Speakers

802.11n

Antenna

Antenna

Antenna

Ambient

Temperature

Sensor

Speakers

iMac (27-inch, Mid 2011) General Troubleshooting 31

Functional Overview: Front of Logic Board

Refer to this diagram for symptoms related to connectors on the front of the logic board.

To rotate this page in Preview for easier viewing, go to Tools menu and choose “Rotate Left”.

- no IR Remote functionality

IR Receiver:

pads on logic board)

- no Power On (unless shorting the

- freezes, or kernel panics

RAM:

- no boot

- beep tones on startup

Backup Battery:

- no video

- beep tones on startup

- system shutdown if too hot

Power On Button:

- noisy fan perception

- system freezes or kernel panic

Ambient Temperature Sensor:

- fans running at higher speed

or blocked

- system shutdown if fan disconnected

- distorted right sound

Right Speaker :

- no sound from right speaker

- system shutdown if too hot

Right Skin Temperature Sensor:

CPU Fan:

- fan running at higher speed

Backlight Power:

- no backlight on display

- hard drive data corruption

- system shutdown if too hot

- fan running at higher speed

- no Bluetooth function

- display brightness does not change when camera is covered with hand

Hard Drive Fan:

- noisy fan perception

- system shutdown if fan

disconnnected or blocked

Camera + Camera LED + Ambient Light Sensor+Bluetooth+ Left Skin

Temperature Sensor:

- no camera function

- no LED when camera is on

2011-08-29

- distorted left sound

Left Speaker :

- no sound from left speaker

AirPort Card:

- cannot enable AirPort

input or output

Audio Board:

Microphone :

- no internal microphone sound input

- no external Optical/Analog audio

- no SD card functionality

- no SD card reader seen in System

Profiler

- system shutdown if too hot

- fan running at higher speed

SD Card Reader:

Optical Drive Temperature Sensor:

- media burning fail

Optical Drive Fan:

- noisy fan perception

- system shutdown if fan disconnected

or blocked

DisplayPort Panel Data:

- poor / no video on internal display

DisplayPort Power:

- poor / no video on internal display

iMac (27-inch, Mid 2011) General Troubleshooting 32

Functional Overview: Back of Logic Board

Refer to this diagram for symptoms related to connectors on the back of the logic board.

To rotate this page in Preview for easier viewing, go to Tools menu and choose “Rotate Left”.

DC Power In:

- no power

- no boot from hard drive

- no hard drive seen on SATA bus

SATA Hard Drive Data:

- system shutdown if too hot

- fan running at higher speed

MXM Video Card:

- no video on internal LCD and external ThunderBolt connector

- video artifacts

MXM Video Card Temperature Sensor:

- no boot from hard drive

SATA Hard Drive Power:

- no hard drive seen on SATA bus

- drive does not inject media

- no boot from optical drive

- no optical drive seen on SATA bus

CPU Temperature Sensor:

- system shutdown if too hot

- fan running at higher speed,

- no boot from SSD

SATA Optical Drive Data + Power:

SATA SSD Data + Power:

- no SSD seen on SATA bus,

2011-08-29

iMac (27-inch, Mid 2011) General Troubleshooting 33

Symptom Charts

Follow steps in the order indicated below. If an action resolves the issue, retest computer to
verify.

Startup and Power

No Power

Unlikely cause: speakers

Quick Check

Symptoms Quick Check

No Power

• No power

• No fan spin

• No startup sound

• No image on external display

• No hard drive or optical drive
activity

• Caps Lock LED on wired
keyboard doesn’t light when
pressed.

1. Verify power source.

2. Verify power cord.

3. Listen closely for signs of activity from system

including: rotating fans, hard drive or optical drive
activity, startup sound, etc.

4. Disconnect all peripherals.

5. Reset SMC.

Deep Dive

Check Result Action Code

1. Attempt normal startup. Press

power button to start up
computer. Does the computer
exhibit any signs of power
activity, such as fan or hard
drive activity, startup sound
or Caps Lock LED on wired
keyboard?

Yes Go to step 2.

No Go to step 4.

2011-08-29

2. Verify display functionality.
Conrm whether a video signal
appears on the display. Is a
video image clearly visible on
the display?

Yes Run Mac Resource Inspector

(MRI) to obtain latest
test results. Redirect to
appropriate symptom.

No Go to step 3.

iMac (27-inch, Mid 2011) Symptom Charts — Startup and Power 34

3. Verify video without backlight.
On a display with dim or
no backlight, shine an LED
ashlight through the glass on
the front of the display to check
for video signal. Is any video
visible with ashlight?

Yes Go to Backlight Issue / No

Backlight symptom ow.

No

Go to No Video symptom
ow.

4. Disconnect power cord.
Carefully inspect the
connectors between AC
inlet and power supply, then
DC connectors and cables
between power supply and
logic board, for damage or poor
connections.

5. Inspect power button and
verify if it is properly connected
to the logic board.

6. Disconnect power button from
logic board. Inspect cable and
connector for damage. Using a
multimeter (set as ohmmeter),
verify continuity between the
two pins of the power button
when it is pressed.

7. Reconnect power cord. Press
power button and verify if
system turns ON. You may
alternately check for diagnostic
LED # 2 to illuminate when the
power button is pressed. See
the section on Diagnostic LEDs
for more information.

Yes Reseat misconnected cable(s),

or replace damaged one(s).

No Replace DC power cable.

Go to step 8.

Yes Go to step 6.

No Reconnect power button.

Yes Power button is functioning

correctly. Reconnect power
button to logic board and
go to step 7.

No Power button faulty. Replace

rear housing (which includes
power button).

Yes

Power supply functioning. If
computer still won’t boot, go
to No Startup.

No Replace DC power cable.

Go to step 8.

P16

X03

X14

X03

2011-08-29

8. Press power button and verify if
computer turns ON.

Yes Issue solved with replaced DC

power cable.

No Replace power supply.

P01

Go to step 9.

9. Press power button and verify if
computer turns ON.

Yes Issue solved with replaced

power supply.

No Reinstall power supply and

M01

replace logic board.

Note: If No Power symptom persists after all steps have been followed use minimum
conguration troubleshooting to proceed. Try disconnecting hard drive, optical drive, AirPort
card, SD card reader and Bluetooth/camera/sensor cable to determine if one of them is
preventing the power supply from functioning.

iMac (27-inch, Mid 2011) Symptom Charts — Startup and Power 35

No Startup

Quick Check

Symptoms Quick Check

No Startup

• No startup sound or POST
(Power On Self-Test)

• Gray screen appears during
startup

• Some video activity, Apple logo,
spinning gear

• Prohibitory sign or folder with a
ashing question mark

• Startup chime or error beep
tones

• Audible fan, hard drive spin or
optical drive reset sounds

• Sleep LED on, blinking or went
out.

• Caps Lock LED on wired
keyboard toggles on and o
when pressed

1. Verify that the startup process passes initial
memory checks and POST (Power On Self-Test)
with a normal startup sound—but no beeping
sounds—with some video activity.

If computer generates beeping sounds there may
be an issue with the memory. See Apple Support
article HT2341: Intel-based Mac Power On Self

Test RAM error codes.

2. Disconnect all external peripherals and Ethernet

cables.

3. Reset SMC.

4. Reset PRAM by holding down Command-Option-

P-R keys while restarting, until you hear the
startup sound for the second time.

5. Start up from a known-good original system
media or an up-to-date, bootable OS X volume.

6. Run Disk Utility or check Mac Resource Inspector
(MRI) results to verify presence and SMART status
of user’s hard drive.

7. Check the OS X version and build, and refer to
Apple Support article HT1159: OS X versions

(builds) for computers to make sure system

build is the correct version for this computer
model.

2011-08-29

8. Hold Shift key during startup to put computer
into Safe Mode. See Apple Support article

HT1564: OS X: What is Safe Boot, Safe Mode?

9. Identifying when in the startup process the

computer hangs can help isolate the issue. See
Apple Support article HT2674: Intel-based Mac:

Startup sequence and error codes, symbols.

iMac (27-inch, Mid 2011) Symptom Charts — Startup and Power 36

Deep Dive

Check Result Action Code

1. Verify whether computer will

start up to Apple Hardware Test
(AHT).

2. Remove installed memory, and
test with known-good memory.
Verify whether computer starts
up properly now.

3. Wait 15 seconds after computer
powers down, then disconnect
AirPort card from logic board.
Verify whether computer starts
up properly now.

4. Verify whether computer will
start up properly from known­good original system media or
an up-to-date, bootable OS X
volume.

Yes Run the extended tests

and proceed with results. If
AHT passes or boots with a
memory error, go to step 2.

No Go to step 2.

Yes Memory issue. Reinstall one

of user’s memory modules
and retest. Proceed one by
one to nd the faulty memory
module, and replace it.

No Go to step 3.

Yes

No Go to step 4.

Yes

No Go to step 5.

Go to AirPort Card Kernel

Panic.

Go to Hard Drive or SSD Not

Recognized.

X02

5. Remove hard drive. Verify

whether computer will start
up properly from known-good
original system media or an up­to-date, bootable OS X volume.

6. Disconnect optical drive cable
and retest. Verify whether
computer starts up properly
now.

7. Remove coin battery on front
of logic board and leave out for
approximately 1 minute. Then
reinstall battery. This will reset
logic board. Verify whether
computer starts up properly
now.

Yes Replace hard drive. H01

No Go to step 6.

Yes Reconnect optical drive and

go to Optical Drive Not

Recognized.

No Go to step 7.

Yes Issue resolved by logic board

reset. Measure DC voltage on
battery touching battery with
red probe, and grounding
with black probe. If voltage is

2.7v or less, replace battery.

See Apple Support article

HT3250: Diagnostics: Using
a digital multimeter.

No Replace logic board. M02

2011-08-29

iMac (27-inch, Mid 2011) Symptom Charts — Startup and Power 37

Intermittent Shutdown

Troubleshooting Shutdown Causes

Always run the latest Apple service diagnostics to check for any abnormal value reading from a
thermal, a voltage, or a current sensor, or from a fan speed meter. The log les may also report
the cause of a previous shutdown(s).

Collect all available info from user on shutdown occurrence details: periodicity, power state
when issue happens, running applications, running time before shutdown.

Shutdown events can be categorized into four dierent areas.

1) User-related shut downs:

A computer shutdown event may be caused by user operation. The following shutdown
methods should not be considered as a failure, unless the power button is found to be
defective.

• Choosing “Shut Down” from the Apple () menu.

• Pressing and holding the power button for 10 seconds.

• Programming a timed shutdown in System Preferences > Energy Saver.

Suggested troubleshooting steps are:

• Reset SMC.

• Check System Preferences > Energy Saver settings.

• Test the power button for an intermittent short that would force computer to shutdown.

2) Activity-related shutdowns:

• Computer could not complete the standard shutdown process and had to force shutdown.

• An installed watchdog detected that an application did not respond within specied time
(this watchdog can be enabled in OS X Server Energy Saver preferences).

These shutdowns may be linked to system preferences, device drivers, applications, or
operating system freezes.

Suggested troubleshooting steps are:

• Check the system logs and Activity Monitor for clues on the freezing process.

• Check for and apply the latest software and rmware updates for installed device drivers,
applications, or operating system.

• Start up from known-good original system media or an up-to-date, bootable OS X volume.

2011-08-29

iMac (27-inch, Mid 2011) Symptom Charts — Startup and Power 38

3) Power-related shutdowns:

• External power source was removed.

Power-related shutdowns are due to power management, poor connections, or defective
power sources.

Suggested steps for troubleshooting are :

• Reset SMC.

• Verify the following cables are securely connected: external power cord, AC inlet, and
internal DC power cable.

4) Hardware-related shutdowns:

• One of the thermal sensors reached a specied temperature limit.

• One of the voltage sensors reached a specied voltage limit.

• One of the current sensors reached a specied current limit.

These shutdowns are due to temperature, voltage, current, fan speed or other hardware-related
sensor values getting out of range.

Suggested steps for troubleshooting are:

• Check for all sensors connections and values using the latest Apple service diagnostics and
locate sensors using the table in the General Troubleshooting chapter.

• Check /listen for fan(s) operation.

• Check cleanliness of the heat sink ns and the air ow.

For additional information, continue to Quick Checks on the next page.

2011-08-29

iMac (27-inch, Mid 2011) Symptom Charts — Startup and Power 39

Quick Check

Symptoms Quick Check

Intermittent Shutdown

• Shuts down during startup

• Shuts down unexpectedly
during use

• Restarts spontaneously

• Shuts down when waking from
sleep

1. Collect details from the user regarding shutdown
occurrence and system conguration: when
it happens (e.g., after running for a while);
frequency of shutdowns; which applications are
running; and shutdown repeatability. If shutdown
can be easily reproduced, check next steps.

2. Make sure that power cord is securely attached
to the back of computer, and is not hindered by a
desk or other furniture.

3. Plug computer directly into an AC outlet to test if
a surge protector or UPS is causing issue.

4. Open System Preferences > Energy Saver >
Schedule and make sure that a “Shut Down”
event is not scheduled.

5. Hold Shift key during startup to put computer
into Safe Mode. See Apple Support article

HT1564: OS X: What is Safe Boot, Safe Mode?

6. Start up from known-good original system media

or an up-to-date, bootable OS X volume.

7. Run Mac Resource Inspector (MRI) to check
fan (motor) and thermal sensors detection and
values.

8. Reset SMC.

9. Reset PRAM by holding down Command-Option-

P-R keys while restarting, until you hear the
startup sound for the second time.

10. Run Apple Service Diagnostic (ASD) for looping
extended sensors + thermal tests.

2011-08-29

iMac (27-inch, Mid 2011) Symptom Charts — Startup and Power 40

Deep Dive

Check Result Action Code

1. Activity related shutdowns:

Reset SMC and PRAM and
verify that shutdown issue still
happens.

2. Start up from a known-good
original system media or an up­to-date, bootable OS X volume,
and verify whether shutdown
issue still happens.

3. Power related shutdowns:
With known-good AC power
cord and AC outlet, verify if
computer continues to restart
or shutdown

4. Disconnect hard drive power
cable from hard drive and
startup computer from a
known-good original system
media or an up-to-date,
bootable OS X volume. Verify
whether computer continues to
restart or shutdown.

Yes Check with known-good

bootable drive. Go to step 2.

No Shutdown cause was related

to SMC or PRAM programmed
shutdown settings or
corruption, and was resolved
by reverting them to default
settings.

Yes Go to step 3.

No Reinstall OS on user’s drive.

Check for and apply the
latest software and rmware
updates.

Yes Go to step 4.

No AC power cord / outlet issue.

Issue resolved.

Yes Go to step 5.

No

Possible bad software or hard
drive. Go to Hard Drive or

SSD Not Recognized.

X03

2011-08-29

5. Inspect and reseat AC inlet
connection to power supply
(the smaller of the 2 cables
connected to power supply),
and DC power cable from
power supply to logic board.
Verify whether damage is
observed on the cables or
connectors.

6. Install known-good power
supply. Verify whether
computer continues to restart
or shutdown.

Yes Replace damaged cable.

Retest. Return to step 1 if
problem continues.

No Go to step 6.

Yes Reinstall original power

supply. Go to step 7.

No Issue resolved with power

supply replacement.

iMac (27-inch, Mid 2011) Symptom Charts — Startup and Power 41

X03

P02

7. Replace DC power cable,

which supplies power to logic
board, hard drive, and LED
backlight board. Verify whether
computer continues to restart
or shutdown.

Yes Go to step 8.

No Issue resolved with DC power

cable replacement.

X03

8. Hardware-related shutdowns:

Run latest available Apple
service diagnostics and verify if
a sensor failure is reported.

9. Verify whether a thermal sensor
or fan failure is reported by
diagnostics.

Yes -If a temperature or a fan

sensor failure is reported, go
to step 9.

-If a voltage or a current
sensor failure is reported test
with known-good power
supply board. If issue persists,
replace logic board.

No Setup ASD’s looping tests

and go to step 9. If no failure
is found, return computer to
user for no failure found.

Yes -If fan not running failure,

check for fan cable seating
and retest. If same failure
after retest replace fan with
known-good fan and retest.
If issue does not happen with
known-good fan, replace
user’s fan.

-If an over temp failure
reported, check for cause of
over temp, like obstructed
vent, dust in heat sink n,
clogged fan and retest. If still
failing replace part where
sensor is located (logic board,
power supply, hard drive or
sensor cable) according to
the sensor location table
in General Troubleshooting
chapter. Go to step 10.

M23

X22

M23

P17
X03

2011-08-29

10. Isolate if issue solved
Verify whether shutdown/issue
does is xed.

No Go to step 10.

Yes Issue resolved.

No Replace logic board with

corresponding symptom:

-if for thermal error cause

-if for other cause

iMac (27-inch, Mid 2011) Symptom Charts — Startup and Power 42

M18
M08

Kernel Panic / System Crashes

Quick Check

Symptoms Quick Check

Kernel Panic / System Crashes

• Computer displays a kernel
panic alert message
See Apple Support article

HT1392: “You need to restart
your computer” (kernel panic)
message appears (OS X v10.5,

10.6)

• Computer freezes during use

• Computer freezes upon wake
from sleep

• Computer freezes when AirPort
is enabled or activated

1. Collect details from user regarding the kernel
panic or crash: when does it happen; what
peripherals are in use; what applications are in
use; what actions are taking place at the time;
and try to establish a set of circumstances so you
can recreate the issue eectively.

2. Check for and apply the latest software and
rmware updates.

3. Remove suspected external devices.

4. Verify memory conguration matches actual

amount of installed physical memory.

5. Hold Shift key during startup to start computer in
Safe Mode. See Apple Support article HT1564: OS

X: What is Safe Boot, Safe Mode?

6. Start up from known-good bootable device with

an up-to-date OS X version and proper build. See
Apple Support article HT1159: OS X versions

(builds) for computers.

7. Check kernel panic log le to look for crash cause.

See Apple Support articles HT2546: OS X: How

to log a kernel panic, and HT1392: “You need to
restart your computer” (kernel panic) message
appears (OS X v10.5, 10.6).

2011-08-29

8. If issue cannot be easily reproduced, run Apple
Service Diagnostic (ASD) for longer, looping or OS
tests.

Deep Dive

Check Result Action Code

1. Start up computer to Apple

Hardware Test (AHT) on internal
hard drive or an inserted Install
DVD by holding down the D
key at startup. Verify whether
computer boots up from any of
these volumes.

iMac (27-inch, Mid 2011) Symptom Charts — Startup and Power 43

Yes Run extended tests and

proceed with results. If AHT
passes or boots with a kernel
panic, go to step 2.

No Go to step 2.

2. Remove all peripheral devices
including keyboard and mouse.
Verify whether computer starts
without kernel panic.

Yes Add peripheral devices one

at a time until kernel panic
repeats. Replace device
causing issue.

No Go to step 3.

3. Use known-good memory in
the system. Verify whether
computer start without kernel
panic now.

4. Wait for 20 seconds after
shutdown and disconnect
AirPort card from logic board.
Verify whether computer starts
without kernel panic now.

5. Disconnect data cable from
hard drive and startup to the
Install DVD in the optical drive
or from an external volume.
Verify whether computer starts
without kernel panic now.

6. Disconnect Bluetooth/camera/
sensor cable and microphone
cable from logic board. Verify
whether computer starts
without kernel panic now.

Yes Install user’s memory one

by one and retest. If kernel
panic repeats, replace aected
memory. Verify whether
correct memory specication
is being used.

No Go to step 4.

Yes Go to AirPort Card Kernel

Panic.

No Go to step 5.

Yes

Go to Hard Drive or SSD Not

Recognized.

No Go to step 6.

Yes Go to AirPort Issues,

Bluetooth Issues, Camera
Issues or Microphone Issues

symptom ow as appropriate.

No Go to step 7.

X01

2011-08-29

7. Disconnect SD cable on logic
board. Verify whether computer
starts without kernel panic
now.

8. Disconnect optical drive and
test. Verify whether computer
starts without kernel panic
now.

Yes

Go to SD Memory Card Not

Recognized.

No Go to step 8

Yes Go to Optical Drive Not

Recognized.

No Replace logic board. M06

iMac (27-inch, Mid 2011) Symptom Charts — Startup and Power 44

No Video

Unlikely cause: hard drive, optical drive, speakers, camera

Quick Check

Symptoms Quick Check

No Video

• Power but no video visible on
display

• Fan, hard drive spin or optical
drive reset sounds audible

• Caps Lock key on wired
keyboard illuminates when
pressed

1. Press F2 key on wired keyboard to increase
screen brightness.

2. For no-video issues, connect a compatible
external display to verify if iMac video circuitry is
functioning. If image appears on external display
go to Backlight Issue/No Backlight.

3. Reset SMC.

4. Reset PRAM by holding down Command-Option-

P-R keys while rebooting, until you hear the
startup sound for the second time.

Deep Dive

Check Result Action Code

1. Verify startup sound present

and fans running when
computer powered ON. (Reset
SMC and PRAM, reseat battery
on logic board if necessary and
retest for proper start up.)

2. Verify whether image is visible
on built-in LCD panel.

Yes Power ON self test OK. Boot

sequence started.
Go to step 2.

No Go to No Startup.

Yes Video present. Verify

computer functionality and
return to user or jump to
appropriate troubleshooting
ow.

2011-08-29

3. Connect supported external
display. Verify whether image
appears on external display
when computer is started up.

No Go to step 3.

Yes

No Go to step 4.

iMac (27-inch, Mid 2011) Symptom Charts — Startup and Power 45

External display detected by
system. Video circuitry on
logic board functional.

Inspect DisplayPort cable
connection to back of LCD
panel. Reseat and test again.
If you continue to have
problems go to Backlight

Issue/No Backlight.

4. Disconnect AC, remove glass

and LCD panel to access

diagnostic LEDs on center of

logic board. Reconnect AC and
verify if LED #3 turns on shortly
after computer powers on.

Yes Logic board communicating

with video card. Go to step 5.

No If LED #3 does not turn ON

reseat video card and retest,
then replace video card and
repeat step 4. If issue persists,
replace logic board.

M03

M03

5. Locate diagnostic LEDs on

logic board and verify if LED #4
turns on shortly after computer
powers on.

6. Locate diagnostic LEDs on the
logic board and verify if LED #4
turns on shortly after computer
powers on.

Yes Logic board communicating

with LCD panel. Go to

Backlight Issue/No
Backlight.

No Replace DisplayPort cable.

Go to step 6.

Yes Video controller functional

and communicating with LCD
panel. Go to Backlight Issue/

No Backlight.

No Video controller unable to

communicate with LCD panel.
Reseat cables rst. If issue
persists, replace LCD panel.
Retest.

X03

L03

2011-08-29

iMac (27-inch, Mid 2011) Symptom Charts — Startup and Power 46

Corrupted Video

Unlikely cause: power supply, hard drive, optical drive, fans, speakers, camera

Quick Check

Symptoms Quick Check

Corrupted Video

• Text and graphics appear fuzzy

• Image corrupted

1. Check Apple Support article HT1159: OS X

versions (builds) for computers to make sure

system build is correct for this computer model.

2. Set System Preferences > Displays to native
resolution of LCD. Non-native resolutions are
unable to produce optimal clarity.

3. In System Preferences > Appearance, turn o text
smoothing for smaller fonts. Smaller fonts can
appear fuzzy or harder to read when smoothing
(or “antialiasing”) is on. Ask user if this resolves
their issue.

4. Clean outside surface of glass panel.

5. Check for and apply the latest software and

rmware updates.

6. Start up from known-good original system
media or an up-to-date, bootable OS X volume
to determine whether a potential software/driver
issue exists.

7. When issue occurs, take a screenshot (Command­Shift-3). View screenshot le on a known-good
computer. If image corruption can be seen in the
screenshot then issue is with the video drivers,
software, or video/logic board. If issue cannot
be seen in the screenshot then LCD panel and
DisplayPort cable should be tested further.

2011-08-29

Deep Dive

Check Result Action Code

1. Start up from known-good

original system media or an up­to-date, bootable OS X volume
and verify whether issue is still
visible.

2. Verify whether issue is visible
on an external display.

iMac (27-inch, Mid 2011) Symptom Charts — Startup and Power 47

Yes Go to step 2.

No Issue likely caused by

software or driver issue.
Troubleshoot for software
issues.

Yes Issue is NOT caused by

internal LCD display.
Go to step 3.

No Go to step 6.

3. Remove video card, inspect
connector for damage or
corrosion. Reinstall video card
and retest. Verify whether issue
still occurs.

Yes Replace video card.

Go to step 4.

No Issue resolved by reseating

video card.

M04

4. Verify whether video corruption

issue is still present.

5. Verify whether video corruption
issue is still present with
replacement logic board
installed.

6. Inspect glass panel. Verify
whether issue is caused by
condensation or contaminants
on inside/outside surface of
glass panel, or on surface of
LCD panel.

Yes Replace logic board. If a video

card was replaced, reinstall
user’s video card. Go to step 5.

No Issue resolved with

replacement video card.

Yes Return to step 1 and retest.

No Issue resolved with

replacement logic board.

Yes Clean glass and/or LCD using

procedures in Glass Panel
take-apart chapter.

Identify possible sources
of contamination (nearby
cigarette/cooking smoke,
heavy airborne dust, etc.)
to prevent recurrence.
Condensation should
dissipate after computer has
been running a few hours.

No Go to step 7.

M04

2011-08-29

7. Disconnect DisplayPort cable
between LCD panel and logic
board, and verify if there is
damage to cable or connectors.
Repeat with v-sync cable
connected between LCD panel
and LED backlight board.

8. Verify whether issue is still
visible after reinstalling/
replacing DisplayPort cable and
v-sync cable.

Yes Replace DisplayPort cable

X03

or any other damaged part/
module.

No Reinstall DisplayPort cable

and v-sync cable.
Go to step 8.

Yes If video corruption symptom

appears to be like a rolling
image (bad location of the
top of image), replace v-sync
cable and go to step 9.

Else replace DisplayPort cable

X03

X03

and go to step 9.

No Issue resolved with reseating/

replacing damaged cable(s).

iMac (27-inch, Mid 2011) Symptom Charts — Startup and Power 48

9. Verify whether issue is
still visible after replacing
DisplayPort cable or/and v-sync
cable.

Yes Replace LCD panel. L04

No Issue resolved with replacing

the cable(s).

10. Verify whether issue is still
present with replacement LCD
panel installed.

Yes Contact Apple Technical

Support.

No Issue resolved with

replacement of LCD panel.
Run Apple Service Toolkit Test
Patterns Tool test to verify
display.

L04

2011-08-29

iMac (27-inch, Mid 2011) Symptom Charts — Startup and Power 49

Burnt Smell/Odor

Unlikely cause: speakers, rear housing

Quick Check

Symptoms Quick Check

Burnt Smell/Odor

• Burning smell

• Unusual odor

1. Verify that computer is the source of the odor.

2. If computer is new, see Apple Support article

TA22044: New Equipment: Odors May Be
Present Short-Term.

3. Disconnect all third-party devices and check to

see if any external device is the source of odor.

4. Determine if this is a safety issue. Refer to Apple
Support article CP1124: SERVICE: Handling

Potential Product Safety Issues.

5. Do a quick inspection of enclosure and

components for obvious signs of burning or
smoky residue. Check rear vents, keyboard, slots,
and ports, as well as power cord.

6. Clean enclosure to eliminate any causes from
external contamination. Refer to Apple Support
article HT3226: How to clean Apple products.
Explain the cause to user.

7. Inspect air intake and air outlets for obstructions.
To prevent overheating make sure there
is sucient clearance to allow air to ow
unobstructed into and out of the computer.

2011-08-29

8. Verify if computer is functional.

Deep Dive

Check Result Action Code

1. Verify whether source of

the odor can be identied
by visually inspecting each
module and its associated
cables for signs of burned or
damaged components, smoke
residue, burned traces, or
melted or damaged wiring,

iMac (27-inch, Mid 2011) Symptom Charts — Startup and Power 50

Yes Replace aected module(s).

Go to step 2

No Unable to locate source of

odor. Go to step 3.

P08

2. Disconnect all third-party

devices and cables. Power on
computer and verify if smoke
or strong odor returns.

Yes Power down computer

immediately. Go to step 3.

No Computer functions correctly.

Verify third-party devices and
cables. Consult third-party
companies as needed for
issues with those products.

3. Verify whether source of odor
can be located using your nose.

Yes Check all AC and DC power

No Contact Apple for assistance

Uncategorized Symptoms

Quick Check

Symptoms Quick Check

Uncategorized Symptoms

• Unable to locate appropriate
symptom code.

1. Make sure computer is plugged into a known­good outlet.

2. Listen for startup sound, fan, optical drive, or hard
drive noise which indicates computer is powering
up. If noise is heard, go to No Startup. If no noise
is heard go to No Power.

P08

cables for pinch or damage.
Replace aected module(s)
and retest.

if you feel that there is a
possible safety issue with
computer.

2011-08-29

3. Attempt to start up from known-good original
system media or an up-to-date, bootable OS X
volume to isolate possible software issues.

Deep Dive

Check Result Action Code

1. Verify whether existing

symptom code applies to issue
reported by user.

iMac (27-inch, Mid 2011) Symptom Charts — Startup and Power 51

Yes Jump to appropriate

symptom code ow.

No

Document reported failure
and send feedback to

[e-mail]

stating that a suitable
symptom code wasn’t found.
Provide as much detail as
possible.

N99

Display

Backlight Issue/No Backlight

Unlikely cause: hard drive, optical drive, speakers, camera

Quick Check

Symptoms Quick Check

Backlight Issue/No Backlight

• Display not illuminated

• Flickering, unstable or non­uniform background lighting

• Poor backlight at some or all
settings

• Computer exhibits power, POST
chime and fan movement

1. Cover ambient light sensor to mimic a dark room,
and adjust brightness to maximum setting using
F2 key on wired keyboard.

2. Reset PRAM by holding down Command-Option­P-R keys while restarting, until you hear the
startup sound for the second time.

3. Reset SMC.

4. If no image on built-in display, connect supported

external display to verify if iMac video circuitry
is functioning. If no image visible on external
display, go to No Video symptom ow under
Startup and Power.

Deep Dive

Check Result Action Code

1. Verify startup sound present

and fans running when
computer powered ON. (Reset
SMC and PRAM if necessary for
proper start up.)

Yes Power on self test OK.

Go to step 2.

No Go to No Startup symptom

ow.

2011-08-29

2. Verify if image is visible on
built-in LCD panel, with
adjustable backlight level.

3. Connect supported external
display. Verify if any image
appears on external display
after system has started up.

Yes Video present. Verify

computer functionality
and return to user or go to
appropriate troubleshooting
ow.

No Go to step 3.

Yes External display detected by

system. Video circuitry on
logic board functional.
Go to step 4.

No Go to No Video symptom

ow.

iMac (27-inch, Mid 2011) Symptom Charts — Display 52

4. In System Preferences > Display,
set brightness to maximum.
Verify if LCD backlight is ON
by looking for faint glow
from display when viewed in
darkened room.

Yes Able to adjust brightness in

System Preferences and faint
glow seen. Go to step 7.

No Unable to adjust brightness

in System Preferences, or no
faint glow. Go to step 5.

5. Shine bright (low heat)
ashlight onto front of LCD.
With computer powered ON
verify if a faint image is visible.

6. Power on computer. Verify if
image is now visible on LCD
panel with correct backlight
level.

Yes LCD panel functional but

backlight is missing or
dim. Remove LCD panel
and inspect and reseat the
following cable connections:

-Output cable between lower
end of LED backlight board
and lower end of LCD panel.

-Vertical sync cable between
upper end of LED backlight
board and LCD panel.

-DC power cable between
upper right of LED backlight
board and power supply.

Replace any damaged cable.
Reinstall LCD panel and go to
step 6.

No No image or backlight.

Go to step 7.

Yes Issue resolved.

No Replace LED backlight board.

Retest. If issue persists, go to
step 7.

X03

M04

2011-08-29

7. Inspect and reseat DisplayPort
cable between LCD panel
and logic board. Power on
computer. Verify if image is
visible on built-in LCD display.

Yes Issue resolved.

No Replace DisplayPort cable.

If issue persists, replace LCD

X03

L03

panel. Retest.

iMac (27-inch, Mid 2011) Symptom Charts — Display 53

Noise / Unstable Flickering

Quick Check

Symptoms Quick Check

Noise / Unstable Flickering

• Flickering image

• Horizontal bands of static
intermittently appear

• Dock and/or menu bar shift
positions

• Display intermittently ashes
on/o

• Unstable image

• Humming noise from display

• High frequency noise from
display

1. If display icker only occurs when the brightness
level is set below maximum, then go to Deep
Dive step 6 to verify that the v-sync cable is
properly connected.

2. Check for and apply the latest software and
rmware updates.

3. Check Apple Support article HT1159: OS X

versions (builds) for computers to make sure

system build is correct for this computer model.

4. Verify that intake vents on bottom of computer
are not obstructed.

5. Inspect system for third-party software that is
being used to set fan speeds to a higher than
normal RPM. Some users may install this software
to monitor and control internal temperatures,
potentially causing higher fan speeds to generate
higher than expected noise levels.

Deep Dive

Check Result Action Code

1. Verify if user issue is due to

ickering, or to an unstable
video image on the LCD.

2. Connect a known-good
supported external display.
Verify if issue occurs on both
the internal and the external
display.

3. When display ickers, verify
whether one of the following
symptoms occurred:

- Flickering image

- Horizontal bands of static

- Dock and/or menu bar shift
positions

- Display ashes on/o

Yes Suspected ickering issue.

Go to step 2.

No For audible noise issues go to

step 8. For all other issues go
to appropriate symptom ow.

Yes Suspect issue with video

circuitry. Go to Corrupted

Video symptom ow.

No Video circuitry appears OK.

Go to step 3.

Yes Remove glass and LCD panel.

Check , reseat, and secure
the DisplayPort cable to both
ends. Check and reseat the
v-sync cable to both ends.
Go to step 4.

No LCD panel OK.

Go to step 4.

2011-08-29

iMac (27-inch, Mid 2011) Symptom Charts — Display 54

4. Power ON computer and verify
if issue still occurs.

Yes If connections are secure and

display is still ickering, go to
step 5.

No Issue resolved.

5. Carefully disconnect and
verify if any of the four cables
on back of LCD panel show
signs of damage, corrosion, or
pinched wires.

6. Verify whether ickering occurs
when brightness level is set
below max.

7. Verify if ickering issue is still
present.

8. Verify if high pitch noise varies
when adjusting brightness level
up and down.

Yes Replace and damaged

X03

cable(s) and retest.

No Go to step 6.

Yes Image present but backlight

is ickering. Replace v-sync
cable and retest. If issue

X03

persists, replace LED backlight
board.

No Replace DisplayPort cable,

M04

X03

retest and go to step 7.

Yes Replace LCD panel. L06

No Issue resolved.

Yes Inspect and replace the

v-sync cable if it is damaged,

X03

otherwise replace LED
backlight board.

M04

If issue persists, replace power
supply.

P01

No Noise is from another source.

9. Verify if noise can be heard

Yes Replace LED backlight board.
when computer is set up with
user seated in normal user
position. Adjusting brightness

No Noises that are not audible

level up and down may be
necessary to recreate issue.

10. Verify if noise is still present. Yes

No Issue resolved.

Go to step 9.

M04

Go to step 10.

from the normal user position
are considered acceptable.

If noise still present, go
to Noise/Hum/Vibration
symptom ow.

2011-08-29

iMac (27-inch, Mid 2011) Symptom Charts — Display 55

LCD Image Issues

Unlikely cause: power supply, hard drive, optical drive, fans, speakers, camera

Quick Check

Symptom Quick Check

LCD Issues

• Incorrect/missing colors

• Distorted/blurred image

• Pixel anomalies

• Vertical/horizontal lines

• Non-uniform brightness

• Flickering

1. If display icker only occurs when the brightness
level is set below maximum, then go to Backlight

Issue/No Backlight symptom ow.

2. Check for and apply the latest software and

rmware updates.

3. Check Apple Support article HT1159: OS X

versions (builds) for computers to make sure

system build is correct for this computer model.

4. Isolate software by starting up from known-good
original system media or an up-to-date, bootable
OS X volume.

5. Allow display to warm up for 5 minutes before
evaluating front-of-screen performance.

6. Check System Preferences > Displays > Color for
use of a custom display prole. If so, select “Color
LCD” to revert to default settings.

7. Check brightness setting.

8. Clean glass panel and check for dust or debris.

9. Reset SMC.

2011-08-29

iMac (27-inch, Mid 2011) Symptom Charts — Display 56

Deep Dive: General

Check Result Action Code

1. Verify if user issue is due to

ickering, or to an unstable
video image on the LCD.

2. Verify if issue is incorrect/
missing colors.

3. Verify if issue is distorted/
blurred image.

4. Verify if issue is bright or dark
pixel anomalies.

5. Verify if issue is vertical or
horizontal lines.

6. Verify if issue is non-uniform
brightness.

Yes

No Go to step 2.

Yes

No Go to step 3.

Yes Go to distorted/blurred

No Go to step 4.

Yes

No Go to step 5.

Yes Go to vertical/horizontal

No Go to step 6.

Yes

No LCD functioning OK. Return to

Go to noise / unstable

ickering.

Go to incorrect/missing

colors.

image.

Go to pixel anomalies.

lines.

Go to non-uniform

brightness/color.

appropriate symptom ow if
user issue is still present.

2011-08-29

iMac (27-inch, Mid 2011) Symptom Charts — Display 57

Incorrect/Missing Colors

Unlikely cause: power supply, hard drive, optical drive, fans, speakers, camera

Quick Check

Symptoms Quick Check

Incorrect/Missing Colors

• Wrong color display

• Color/contrast issues

1. Allow display to warm up for 5 minutes before
evaluating front-of-screen performance.

2. Check System Preferences > Displays > Color for
use of a custom display prole. If so, select “Color
LCD” to revert to default settings.

3. Verify System Preferences > Universal Access >
Display “Enhance contrast”, “Use grayscale”, and
“Black on White/White on Black” settings are set
to defaults.

Deep Dive

Check Result Action Code

1. Verify computer has been

warmed up for 5 minutes.

2. Verify if all four cables on back
of LCD panel are secure at both
ends.

Yes Go to step 2.

No Warm up computer for a few

minutes. Go to step 2.

Yes Go to step 3.

No Reseat connections, replace

damaged cable(s) if needed.
Retest.

L14

2011-08-29

3. Go to System Preferences >
Desktop & Screen Saver >
Desktop and set color to Solid
Gray Light. Verify if incorrect/
missing color issue aects
entire display.

4. Set up computer side-by-side
with a known-good, same­model computer showing
same image. Verify if issue is
noticeably worse on display
being tested.

Yes Suspect poor video

connection. Replace
DisplayPort cable between
LCD panel and logic board.

No Go to step 4.

Yes Replace LCD panel. L02

No Small variations in color

uniformity across display are
normal and do not warrant
replacement of LCD.

iMac (27-inch, Mid 2011) Symptom Charts — Display 58

L14

Distorted/Blurred Image

Unlikely cause: power supply, hard drive, optical drive, fans, speakers, camera

Quick Check

Symptoms Quick Check

Distorted/Blurred Image

• Text and graphics appear fuzzy

• Image corrupted

1. If display icker only occurs when the brightness
level is set below maximum, then go to Backlight

Issue/No Backlight symptom ow.

2. Check for and apply the latest software and

rmware updates.

3. Check Apple Support article HT1159: OS X

versions (builds) for computers to make sure

system build is correct for this computer model.

4. Set System Preferences > Displays to native
resolution of LCD. Non-native resolutions are
unable to produce optimal clarity.

5. Clean outside of glass panel.

6. Start up from known-good original system

media or an up-to-date, bootable OS X volume to
determine if a potential software issue exists.

Deep Dive

Check Result Action Code

1. Verify if user issue is due to

ickering, or to an unstable
video image on the LCD.

Yes Flickering issue, go to Noise /

Unstable Flickering.

No Go to step 2. All other issues

go to appropriate symptom
ow.

2011-08-29

2. Start up from Install DVD and
verify if issue is still visible.

3. Verify if issue is visible on an
external display attached to
Thunderbolt port.

Yes Go to step 3.

No Check for and apply the

latest software and rmware
updates.

Check Apple Support article

HT1159: OS X versions
(builds) for computers to

make sure system build is
correct for this computer
model.

Yes Issue NOT caused by internal

LCD panel. Go to step 7.

No Go to step 4.

iMac (27-inch, Mid 2011) Symptom Charts — Display 59

4. Inspect glass panel. Verify if
issue is caused by condensation
or contaminants on inside
surface of glass panel.

Yes Clean glass and/or LCD using

procedures in Glass Panel
take-apart chapter.

Identify possible sources
of contamination (nearby
cigarette/cooking smoke,
heavy airborne dust, etc.)
to prevent recurrence.
Condensation should
dissipate after computer has
been running a few hours.

No Go to step 5.

5. Remove glass and LCD panel.
Disconnect DisplayPort cable
between LCD panel and logic
board, and verify if there is
damage to cable or connectors.

Repeat with v-sync cable
connected between LCD panel
and LED backlight board.

6. Verify if issue is still visible after
reinstalling internal DisplayPort
cable and v-sync cable.

7. Remove video card, inspect
connector for damage or
corrosion then reinstall. Verify if
issue still occurs.

8. Verify if distorted/blurred
image issue is still present.

9. Verify if issue is still present
with replacement logic board
installed.

Yes Replace DisplayPort cable,

X03

v-sync cable or any other
damaged part/module.

No Reinstall DisplayPort cable

and v-sync cable.
Go to step 6.

Yes Replace LCD panel. L04

No Issue resolved.

Yes Replace video card.

Go to step 8.

No Issue likely caused by poor

video card connection.

Yes Replace logic board.

M04

Go to step 9

No Issue resolved.

Yes Return to step 1 and retest.

No Issue resolved.

2011-08-29

iMac (27-inch, Mid 2011) Symptom Charts — Display 60

Pixel Anomalies

Unlikely cause: logic board, power supply, hard drive, optical drive, fans, speakers, camera

Quick Check

Symptoms Quick Check

Pixel Anomalies

• Dark dot anomalies

• Bright dot anomalies

• Debris on inside surface of
glass panel

• Debris on surface of LCD panel

1. Clean outside surface of glass panel.

2. See Apple Support article HT4044: About LCD

display pixel anomalies for Apple products
released in 2010 and later.

Deep Dive

Check Result Action Code

1. Determine if anomalies are

dust/debris on surface of glass
panel or LCD.

2. Determine if bright pixel
anomalies exceed acceptable
number. See Apple Support
article HT4044: About LCD

display pixel anomalies for
Apple products released in
2010 and later.

Yes Clean glass and/or LCD using

procedures in Glass Panel
take-apart chapter.

No Go to step 2.

Yes Replace LCD panel. L08

No LCD panel meets bright pixel

specications. Go to step 3.

2011-08-29

3. Determine if dark pixel
anomalies exceed acceptable
number. See Apple Support
article HT4044: About LCD

display pixel anomalies for
Apple products released in
2010 and later.

4. Determine if combination of

bright/dark pixel anomalies
exceed acceptable number. See
Apple Support article HT4044:

About LCD display pixel
anomalies for Apple products
released in 2010 and later.

Yes Replace LCD panel. L08

No LCD panel meets dark pixel

specications. Go to step 4.

Yes Replace LCD panel. L08

No Explain to user that LCD

panel is operating within
specications for pixel
anomalies. Do NOT replace
LCD panel.

iMac (27-inch, Mid 2011) Symptom Charts — Display 61

Vertical/Horizontal Lines

Unlikely cause: power supply, hard drive, optical drive, fans, speakers, camera

Quick Check

Symptoms Quick Check

Vertical/Horizontal Lines

• Vertical lines

• Horizontal lines

1. Start up from known-good original system
media or an up-to-date, bootable OS X volume to
determine if potential software issue exists.

2. Check for and apply the latest software and
rmware updates.

3. Verify if issue is visible on an external display.

Deep Dive

Check Result Action Code

1. Start up from known-good

original system media or an up­to-date, bootable OS X volume
and verify if issue is still visible.

2. Verify if issue is visible on an
external compatible display.

3. Remove video card and inspect
connector for damage or
corrosion then reinstall. Verify if
issue still occurs.

Yes Go to step 2.

No Issue likely caused by

software or driver issue.
Troubleshoot for software
issues.

Yes Issue NOT caused by internal

LCD. Go to step 3.

No Go to step 4.

Yes Replace video card.

Go to step 8.

No Issue likely caused by poor

video card connection.

M24

2011-08-29

4. Disconnect DisplayPort cable
between LCD display and logic
board, and verify if there is
damage to cable or connectors.

Repeat with vertical sync cable
connected between LCD panel
and LED backlight board.

5. Verify if issue is still present
after reinstalling DisplayPort
cable.

Yes Replace DisplayPort cable

and vertical sync cable or any
other damaged part/module.
Go to step 5.

No Reinstall DisplayPort cable

and vertical sync cable.
Go to step 5.

Yes Replace logic board. If video

card was present, reinstall
original video card.
Go to step 6.

No Issue resolved.

iMac (27-inch, Mid 2011) Symptom Charts — Display 62

X04

M04

6. Verify if issue is still present

with replacement logic board
installed.

Yes Go to step 7.

No Issue resolved.

7. Reinstall original logic board
and verify if issue is still present
with original logic board.

Yes Replace LCD panel. L04

No Issue resolved. If video card

was replaced, reinstall original
video card.

2011-08-29

iMac (27-inch, Mid 2011) Symptom Charts — Display 63

Non-Uniform Brightness / Color

Unlikely cause: power supply, hard drive, optical drive, fans, speakers, camera

Quick Check

Symptoms Quick Check

Non-Uniform Brightness

• Brightness not uniform

• Color not-uniform

1. Verify System Preferences > Displays > Brightness
slider is set above minimum.

2. Allow display to warm up for 5 minutes before
evaluating front-of-screen performance.

3. Visually inspect glass panel for presence of dust,
cigarette smoke, or other contaminants. Clean
glass panel if needed.

4. Run latest available service utilities to check for
correct LCD panel temperature.

Deep Dive

Check Result Action Code

1. Determine if brightness

uniformity issue is visible after
display has warmed up for 5
minutes.

2. Look at user-provided
examples showing brightness
uniformity issue. Determine if
variation in uniformity appears
excessive when compared to
another same-model computer.

Yes Go to step 2.

No Display backlight can take

a few minutes. Retest. If
issue still not visible return
computer to user.

Yes Go to step 3.

No Demonstrate to user that LCD

performs similarly to another
computer of the same model.

2011-08-29

3. Remove glass panel and
loosen screws securing LCD
panel. Determine if brightness
uniformity improves.

4. Remove LCD panel, then
inspect and reseat backlight
cables. Determine if brightness
uniformity improves.

Yes Inspect for mechanical

interference with screws
or cables making contact
with back of LCD. Reseat
components & cables, retest.

No Go to step 4.

Yes One or more backlight cables

were loose.

No Replace LCD panel. L07

iMac (27-inch, Mid 2011) Symptom Charts — Display 64

Cosmetic Issues

Symptoms Quick Check

Cosmetic Issues

• Cracked glass panel

• Cracked LCD

• Scratched LCD polarizer

• Scorched or melted LCD

• LCD impact damage

• Foreign material on LCD or
back side of glass panel.

1. Replace glass panel. Refer to Take Apart/ General
Information/ How to Remove a Broken Glass
Panel.

2. Determine if damage was caused by user
environment, accidental damage, or abuse. If
applicable, inform user that Apple does not
warrant damage caused by accident, abuse,
misuse, ood, re, earthquake, or other external
causes. For more information, refer to:

http://www.apple.com/legal/warranty

3. For dark and bright pixel anomalies see

Pixel Anomalies.

Uncategorized Symptoms

Quick Check

Symptoms Quick Check

Uncategorized Symptoms

• Unable to locate appropriate
symptom code.

1. Make sure brightness level is set above minimum.

2. Clean glass panel to make sure external

contaminants are removed prior to evaluating
display performance.

2011-08-29

3. Allow display to warm up for 5 minutes before
evaluating front-of-screen performance.

Deep Dive

Check Result Action Code

1. Verify if existing symptom code

applies to issue reported by
user.

Yes Jump to appropriate

symptom code ow.

No Document reported failure

and send feedback to

[e-mail]

stating that a suitable
symptom code wasn’t found.
Provide as much detail as
possible.

iMac (27-inch, Mid 2011) Symptom Charts — Display 65

N99

Mass Storage

Hard Drive or SSD Not Recognized

Unlikely cause: LCD panel, power supply, optical drive, fans, speakers, camera

Quick Check

Symptoms Quick Check

Drive Not Recognized
Drive No Boot

• Boots to gray screen

• Boots to blue screen

• Flashing folder with question
mark or prohibitory symbol.
(Review Apple Support article

HT2674: Intel-based Mac:
Startup sequence and error
codes, symbols)

Deep Dive

Important: Always inquire whether the user’s data
has been backed up prior to repair.

1. Disconnect all peripherals and attempt to start

up computer.

2. Use a known-good mouse. A stuck mouse button
will not allow boot.

3. To revert startup drive preferences to their
defaults, reset PRAM by holding down Command­Option-P-R keys while restarting, until you hear
the startup sound for the second time.

4. Start up from known-good original system media
or an up-to-date, bootable OS X volume.

5. Use Mac Resource Inspector (MRI) or Disk Utility
to verify S.M.A.R.T. status of internal drive.

6. Use Target Disk Mode to mount internal drive in
user’s computer on a known-good computer. Use
Disk Utility on host computer to verify S.M.A.R.T.
status of internal drive in user’s computer.

2011-08-29

Check Result Action Code

1. Boot from Install DVD and run

Disk Utility. Verify if user’s drive
is available for Disk Utility to
repair.

2. Run Disk Utility’s “Repair
Disk” function and verify if it
completes successfully.

3. Restart computer. Verify if
system starts up successfully
and that Disk Utility “Verify”
function reports no errors.

Yes Go to step 2.

No Go to step 5.

Yes Go to step 3.

No Go to step 4.

Yes Data error. Issue resolved.

No Go to step 4.

iMac (27-inch, Mid 2011) Symptom Charts — Mass Storage 66

4. With user’s permission, erase
internal drive and reinstall Mac
OS. Verify if installation process
completes.

Yes Go to step 8.

No Go to step 5.

5. Check that the power cable
is correctly connected to the
drive. Inspect drive data and
power cable and connectors for
bent pins, or other damage to
the cable(s).

6. Reseat drive data cable at logic
board and drive ends, and
verify if computer starts up up
successfully.

7. Test with a known-good
bootable drive. Verify if system
starts up successfully and that
Disk Utility “Verify” function
reports no errors.

Yes Replace any damaged data or

power cables.
Go to step 8.

No Go to step 6.

Yes Go to step 8.

No Replace drive data cable. Go

to step 8.

Yes Reinstall user’s drive.

Go to step 9.

No Drive data cable was veried

or replaced, and known-good
drive is installed:

-If hard drive does not spin up
when computer is powered
on, replace hard drive power
cable.

-If hard drive spin up sound
can be heard when computer
is powered on, but computer
cannot boot from it, replace
logic board.

X03

X03

X03

M19

2011-08-29

8. Restart computer. Verify if
system starts up successfully
and that Disk Utility “Verify”
function reports no errors.

9. Restart computer. Verify if
system starts up successfully
and that Disk Utility “Verify”
function reports no errors.

10. Substitute a known-good hard
drive. Boot from system-specic
Install DVD and reinstall OS X
with drive format option. Verify
if drive is formatted correctly
(GUID partition table) and that
software restore was successful.

Yes Issue resolved. Return

computer to user.

No Go to step 7.

Yes Issue resolved.

No User’s drive appears to have

an issue. Go to step 10.

Yes Replace hard drive or SSD as

H01

appropriate.

No Drive data cable veried/

replaced and known-good
drive installed, Check with
known-good restore DVD. If
restore failure still happens,
go to step 11.

iMac (27-inch, Mid 2011) Symptom Charts — Mass Storage 67

11. If restore from Install DVD is
unsuccessful, startup a known­good Intel Mac system with
T key pressed (to enter Target
Disk Mode), insert the iMac
Install DVD in its optical drive
and connect it to the user’s
system via a FireWire cable.
Start up user’s computer while
holding Option key, then select
and boot from the Install
Disc DVD and restore system
software. Verify if software
restore was successful.

Yes Restore failure seems to be

due to user’s internal optical
drive or media issue. Go to

Optical Drive Read/Write
Error.

No Restore failure seems to be

due to internal SATA bus
issue. Replace logic board.

Hard Drive Read/Write Errors

Unlikely cause: LCD panel, power supply, optical drive, fans, speakers, camera

Quick Check

M19

Symptoms Quick Check

Drive Read/Write Error
Drive Bad Sector/Defective
Drive Formatting Issues

• Cannot save documents

• Read/write error message

• Hang when accessing or saving
data

Important: Always inquire whether the user’s data
has been backed up prior to repair.

1. Start up from known-good original system media

or an up-to-date, bootable OS X volume.

2. Use Mac Resource Inspector (MRI) or Disk Utility
to verify S.M.A.R.T. status of internal hard drive.

3. Use Target Disk Mode to mount internal hard
drive in user’s computer on a known-good
computer. Use Disk Utility on host computer to
verify S.M.A.R.T. status of internal hard drive in
user’s computer.

Deep Dive

Check Result Action Code

1. Run Disk Utility ‘Repair Disk’

function, and verify if it
completes successfully.

2. Restart computer. Verify if
system starts up successfully
and that Disk Utility “Verify”
function reports no errors.

Yes Go to step 2.

No Go to step 3.

Yes Data error. Issue resolved. H07

No Go to step 3.

2011-08-29

iMac (27-inch, Mid 2011) Symptom Charts — Mass Storage 68

3. With user’s permission, erase
internal drive(s) containing
OS X, and reinstall it. Verify if
installation process completes.

Yes Go to step 6.

No Go to step 4.

4. Inspect internal hard drive
data and power cables and
connectors for bent pins, or
other damage to the cable.

5. Reseat hard drive data cable
at both hard drive and logic
board. Verify if computer starts
up.

6. Restart computer. Verify if
system starts up successfully
and Disk Utility “Verify” function
reports no errors.

7. Test with known-good
bootable drive. Verify if system
starts up successfully and Disk
Utility “Verify” function reports
no errors.

8. Restart computer. Verify if
system starts up successfully
and that Disk Utility “Verify”
function reports no errors.

Yes Replace damaged cable.

Go to step 6.

No Go to step 5.

Yes Go to step 6.

No Replace hard drive data cable.

Go to step 6.

Yes Issue resolved.

No Go to step 7.

Yes Reinstall user’s drive, go to

step 8.

No Hard drive data cable veried

or replaced and known-good
drive installed used without
success. Replace logic board.

Yes Issue resolved.

No User’s drive appears to be

defective. Go to step 9.

H04

H04

M19

2011-08-29

9. Replace user’s drive. Verify if
drive formats correctly with a
GUID partition map and installs
Mac OS without errors.

Yes Issue resolved by replacing

H03

user’s drive.

No Hard drive data cable veried

M19

or replaced and new drive
did not resolve issue. Replace
logic board.

iMac (27-inch, Mid 2011) Symptom Charts — Mass Storage 69

Hard Drive Noisy

Unlikely cause: LCD panel, logic board, power supply, speakers, camera

Quick Check

Symptoms Quick Check

Hard Drive Noisy

• Noise during start up

• Noise during operation

• Noise when drive is copying or
saving data

Note: Be sure you understand what type of hard
drive noise you should be concerned about, and
what noise you can safely ignore. Not all hard drive
noise is bad; some hard drive noise is normal.

Noises such as occasional quiet chirping or beeping
are typically normal hard drive sounds.

Refer to Apple Support article TS3204: iMac:

Evaluating normal noises, to determine if noise is

within expected range.

Abnormal noises such as grinding, or loud, repeated
clicking, or scraping sounds may be indications of a
more serious issue.

Listen closely in a quiet environment for:

• Noise during start up

• Noise during operation

• Noise when drive is copying or saving data

Important: Always inquire whether the user’s data
has been backed up prior to repair.

1. Verify that user’s issue involves only abnormal

sounds, as dened above.

2011-08-29

2. Compare hard drive noise to a known-good
equivalent computer.

Deep Dive

Check Result Action Code

1. Boot from the Install DVD and

run Disk Utility. Verify if user
hard drive is available for Disk
Utility to repair.

2. Run Disk Utility ‘Repair Disk’
function and verify if it
completes successfully.

3. Restart computer and verify if
the noise is still present.

Yes Go to step 2.

No

Yes Go to step 3.

No Go to step 4.

Yes Go to step 4.

No Issue resolved. Return

iMac (27-inch, Mid 2011) Symptom Charts — Mass Storage 70

Go to Hard Drive or SSD Not

Recognized.

computer to user.

4. Disconnect hard drive data
cable and retest (with an
external display connected).
Verify if the noise is still present.

Yes Noise issue still present, but

does not appear to be caused
by hard drive. Go to Noise/

Hum/Vibration.

No Go to step 5.

5. Remove hard drive and verify
if rubber vibration isolation
grommets are properly
installed in hard drive bracket
(attached to hard drive) and
to mechanism in rear housing
(where hard drive pins insert).

6. Restart system and verify if the
noise is still present.

7. Reconnect user’s drive and,
with user’s permission, erase
hard drive and reinstall Mac
OS. Verify if installation process
completes.

8. Restart system and verify if the
noise is still present.

9. With replacement hard drive
installed, restart computer.
Verify if noise is still present.

Yes Go to step 6.

No If grommets are missing or

damaged, replace hard drive
bracket or mechanism as
appropriate. Go to step 6.

Yes Go to step 7.

No Reseating or replacing the

drive rubber grommets /
bracket solved noise issue.

Yes Go to step 8.

No Replace hard drive.

Go to step 9.

Yes Replace hard drive.

Go to step 9.

No Software related issue.

Yes Replacement hard drive did

not resolve issue. Go to step
10 to check for other source
of noise.

2011-08-29

10. Disconnect hard drive data and
power cables then boot from
the Install DVD. Verify if noise is
caused by fans.

11. Disconnect hard drive and
optical drive then start up from
an external volume. Verify if
noise disappears when optical
drive has been disconnected.

No Issue resolved by replacing

H06

hard drive.

Yes

Go to Fan Failures/Thermal

Issues.

No Go to step 11.

Yes Possible optical drive or

media issue. Go to Optical

Drive Noisy.

No Noise issue still present, but

does not appear to be caused
by hard drive. Go to Noise/

Hum/Vibration.

iMac (27-inch, Mid 2011) Symptom Charts — Mass Storage 71

Optical Drive Not Recognized

Unlikely cause: LCD panel, power supply, fans, speakers, camera

Quick Check

Symptoms Quick Check

Drive Not Recognized/Mount

• Discs inject and eject, but do
not appear in Finder

1. Check Finder Preferences > General and make
sure “CDs, DVDs and iPods” is checked under
“Show these items on the Desktop.”

2. Check aected optical media for presence of
physical damage(s) on its surface.

3. Test with known-good optical media.

4. Use Mac Resource Inspector (MRI), Disk Utility,

or System Information (System Proler in Snow
Leopard) Serial-ATA section to verify if optical
drive is recognized by computer.

5. Check Disk Utility or System Information (System
Proler in Snow Leopard) Serial-ATA section for
presence of an inserted optical media.

6. Check for and apply the latest software and
rmware updates.

7. Refer to Apple Support article HT1159: OS X

versions (builds) for computers, and verify that

the correct version of OS X is installed.

8. Reset PRAM by holding down Command-Option­P-R keys while rebooting, until you hear the
startup sound for the second time.

2011-08-29

9. Reset SMC.

iMac (27-inch, Mid 2011) Symptom Charts — Mass Storage 72

Deep Dive

Check Result Action Code

1. Verify if optical drive is listed

in Serial-ATA section of System
Information (System Proler in
Snow Leopard).

2. Test both CD and DVD media.
Verify if optical drive can read
both CD and DVD media.

3. Connect known-good optical
drive to SATA cable. Verify if
both CD and DVD media are
read reliably.

4. Reseat SATA cable connections
at optical drive and logic board
(cable connects to back of logic
board). Verify if both CD and
DVD media are read reliably.

Yes Go to step 2.

No Go to step 3.

Yes No issue, or possible

intermittent issue. Gather
more information from user.

No If both types of media fail,

check that Finder Preferences
are set to “show CD’s and
DVD’s”, then go to step 3.

If only one type of media fails,
drive has a laser pickup issue.
Replace optical drive.

Yes SATA cable and port on logic

board appear good. Go to
step 5.

No Go to step 4.

Yes Go to step 6.

No Replace optical drive SATA

cable and test.

If issue persists, replace logic
board.

J03

X03

M19

2011-08-29

5. Connect original optical drive
to known-good SATA cable.
Verify if both CD and DVD
media are read reliably.

6. Test read compatible known­good CD and DVD media
(Install DVD). Verify if media is
recognized and reads reliably.

Go to step 6.

Yes SATA cable issue. Replace

SATA cable. Go to step 6.

No Replace optical drive. J03

Yes Issue resolved.

No Replace optical drive. J03

iMac (27-inch, Mid 2011) Symptom Charts — Mass Storage 73

X03

Optical Drive Rejects or Does Not Accept Media

Unlikely cause: LCD panel, power supply, fans, speakers, camera

Quick Check

Symptoms Quick Check

Optical Drive Rejects or Does Not
Accept Media

• Cannot insert a disc into drive

• Drive ejects discs immediately
after insertion

• Cannot eject a disc placed into
drive

1. Check aected optical media for presence of
physical damage(s) on its surface.

2. Use Mac Resource Inspector (MRI), Disk Utility,
or System Information (System Proler in Snow
Leopard) Serial-ATA section to verify if optical
drive is recognized by computer. If drive is not
recognized, go to Optical Drive Not Recognized.

3. Restart computer and hold down mouse button
or keyboard eject key to cycle optical drive.

4. Inspect optical drive slot for obstructions.

Deep Dive

Check Result Action Code

1. Use Mac Resource Inspector

(MRI), Disk Utility, or System
Information (System Proler
in Snow Leopard) Serial-ATA
section to verify if optical drive
is recognized by computer.

2. Verify SATA cable connections
between optical drive and logic
board. Visually inspect cables
and connectors for any debris,
damage or bent pins. Verify if
optical drive is listed in System
Information (System Proler in
Snow Leopard) device tree.

Yes Optical drive communicating

with logic board. Go to step 5.

No Go to step 2.

Yes Optical drive communicating

with logic board. Go to step 5.

No Replace damaged cables

and retest. If connections are
good and no visible cable
damage, go to step 3.

X03

2011-08-29

3. Connect known-good optical
drive to SATA cable. Verify if
known-good optical drive is
listed in the System Information
(System Proler in Snow
Leopard) device tree.

4. With known-good optical drive
installed, test for media inject/
eject. Verify if drive accepts and
ejects known-good media.

Yes Go to step 4.

No Suspect bad SATA cable.

Go to step 7.

Yes Known-good optical drive

resolved inject/eject issue.
Replace optical drive.

No Go to step 7.

iMac (27-inch, Mid 2011) Symptom Charts — Mass Storage 74

J03

5. Inspect optical drive slot during

disc insert/eject. Verify if discs
can be inserted easily and don’t
get scraped during insertion/
ejection.

Yes Go to step 6.

No Verify correct optical drive

bezel alignment with
enclosure. Reseat optical drive
then retest. If issue persists,
replace optical drive.

J03

6. With known-good optical

media (Install DVD), test for
media inject/eject. Verify
if drive accepts and ejects
known-good media.

7. Replace SATA cable then test
for media inject/eject. Verify if
drive injects and ejects known­good media.

Yes Media issue. No repair

necessary. Suggest user
investigate use of dierent
media.

No Go to step 3.

Yes SATA cable resolved issue.

Return computer to user.

No SATA cable veried or

replaced, and optical drive
veried or replaced. Replace
logic board and retest.

X03

M19

2011-08-29

iMac (27-inch, Mid 2011) Symptom Charts — Mass Storage 75

Optical Drive Read/Write Error

Unlikely cause: LCD panel, power supply, fans, speakers, camera

Quick Check

Symptoms Quick Check

Optical Drive Read/Write Error

• Errors when writing optical
media.

• Errors when reading optical
media.

• Hang when accessing or
preparing to write data.

1. Check aected optical media for presence of
physical damage(s) on its surface.

2. Test with known-good optical media.

3. Run Mac Resource Inspector (MRI) to check for

optical drive thermal sensor.

4. Test optical media in a known-good optical drive
in the same type of computer to rule out media
issue.

5. Check with known-good discs like the Install DVD
that came with the computer.

6. For write issues, try lowering the burn speed with
user’s media. Check with known-good media that
performs well in a known-good optical drive of
the same type of computer.

7. Check Disk Utility or System Information (System
Proler in Snow Leopard) Serial-ATA section for
presence of an inserted optical media.

8. Check for and apply the latest software and
rmware updates.

9. Refer to Apple Support article HT1159: OS X

versions (builds) for computers, and verify that

the correct version of OS X is installed.

2011-08-29

10. Reset PRAM by holding down Command-Option­P-R keys while rebooting, until you hear the
startup sound for the second time.

11. Reset SMC.

Deep Dive

Check Result Action Code

1. Verify if media is free to spin

without optical drive scraping
edge or surface of media.

2. Reseat optical drive in rear
housing and verify that a media
can be inserted without being
scratched.

Yes Go to step 3.

No Go to step 2.

Yes Go to step 3.

No Replace optical drive and

retest.

iMac (27-inch, Mid 2011) Symptom Charts — Mass Storage 76

J05

3. Test both CD and DVD media.

Verify if drive can read both CD
and DVD media.

Yes Go to step 7.

No If both types of media fail,

check that Finder Preferences
are set to “show CD’s and
DVD’s”, then go to step 4.

If only one type of media fails,
drive has a laser pickup issue.
Replace optical drive.

J03

4. Install known-good optical

drive and verify if both CD and
DVD media are read reliably.

5. Continue to use known-good
optical drive. Reseat optical
drive cable connection at logic
board ends (cable connects to
back of logic board). Verify if
both CD and DVD media are
read reliably.

6. Reinstall user’s optical drive
and verify if both CD and DVD
media are read reliably.

7. Test write data to compatible
CD and DVD media. Verify if
burned media is recognized
and read reliably.

Yes Both SATA cable and port on

logic board appear good. Go
to step 6.

No Go to step 5.

Yes Go to step 6.

No Replace SATA cable and retest.

If issue persists, replace logic

X03

M19

board.

Go to step 7.

Yes Go to step 7.

No Replace optical drive. J03

Yes Issue resolved.

No Run the lastest Apple service

diagnostic tests for ODD
sensor and ODD fan.

If errors found check
ODD sensor and ODD fan
connections to logic board
(read/write errors may be due
to drive getting too hot).

2011-08-29

If no errors are found, replace

J03

optical drive.

iMac (27-inch, Mid 2011) Symptom Charts — Mass Storage 77

Optical Drive Not Performing to Specications

Unlikely cause: LCD panel, power supply, fans, speakers, camera

Quick Check

Symptoms Quick Check

Optical Drive Not Performing to
Specications

• Read or write speeds slower
than expected

1. Test optical media in another computer of the
same type to rule out media issue.

2. For write issues, check with known-good media
that performs well in another computer and drive
of the same type.

3. Run latest service utilities to check optical drive
thermal sensor status.

Deep Dive

Check Result Action Code

1. Test both CD and DVD media.

Verify if optical drive can read
both CD and DVD media.

2. Connect known-good optical
drive to SATA cable. Verify if
both CD and DVD media are
read reliably.

Yes Go to step 5.

No If both types of media fail,

check that Finder Preferences
are set to “show CD’s and
DVD’s”, then go to step 2.

If only one type of media fails,
drive has a laser pickup issue.
Replace optical drive.

Yes SATA cable and port on logic

board good. Go to step 4.

No Go to step 3.

J03

2011-08-29

3. Reseat SATA cable connections
at optical drive and logic board
(cable connects to back of logic
board). Verify if both CD and
DVD media are read reliably.

4. Connect original optical drive
to known-good SATA cable.
Verify if both CD and DVD
media are read reliably.

5. Test write data to compatible
CD and DVD media. Verify if
burned media is recognized
and read reliably.

Yes Go to step 5.

No Replace SATA cable and test.

If issue persists, replace logic
board.

Go to step 5.

Yes SATA cable issue. Replace

SATA cable. Go to step 5.

No Replace optical drive. J03

Yes Issue resolved.

No Go to step 6.

iMac (27-inch, Mid 2011) Symptom Charts — Mass Storage 78

X03

M19

X03

6. Media that is out of balance

may not perform well at higher
speeds even though higher
speeds may be supported
by the optical drive. Verify if
slowing requested burn speed
allows discs to be written
reliably.

Yes Media issue. No repair

necessary.

No Go to step 7.

7. Test write data to compatible
CD and DVD media. Verify
burned media is recognized
and reads reliably.

Yes Issue resolved.

No Check ODD sensor and ODD

fan in latest service utilities:

If errors found check
ODD sensor and ODD fan
connections to logic board
(read/write errors may be due
to drive being too hot).

If no errors are found while
running diagnostics, replace
optical drive.

J03

2011-08-29

iMac (27-inch, Mid 2011) Symptom Charts — Mass Storage 79

Optical Drive Noisy

Unlikely cause: LCD panel, power supply, fans, speakers, camera

Quick Check

Symptoms Quick Check

Optical Drive Noisy (J04)

• Noise during boot

• Noise during operation

• Noise when drive is copying or
writing data

Note: As a technician, it’s important to know what
optical drive noise you should be concerned about,
and what noises you can safely ignore. The following
lists help distinguish normal, functional optical
drive sounds from noises that may indicate drive
malfunction.

Typical noises include sounds made during the
following activities:

• Waking the computer from sleep

• Burning a CD or DVD

• Inserting a disc

• Ejecting a disc

• Importing (“ripping”) an audio CD in iTunes

• Playing a DVD

• Accessing an idle disc

Abnormal noises include: grinding; loud, repeated
clicking; scraping sounds; or constantly seeking or
cycling the eject mechanism with no disc inserted.

Listen closely in a quiet environment for:

• Noise during start up

• Noise during operation

• Noise when drive is copying or saving data

2011-08-29

1. Test optical media in another computer of the
same type to rule out media issue.

2. Check with known-good discs like the Install DVD
that came with the computer.

3. Verify if noise occurs without media in optical
drive. If so, verify if noise made by hard drive or
fans.

4. Refer to Apple Support article TS3204: iMac:

Evaluating normal noises.

iMac (27-inch, Mid 2011) Symptom Charts — Mass Storage 80

Deep Dive

Check Result Action Code

1. Test optical drive with dierent

source of media. Does the noise
issue remain?

2. Reseat optical drive. Does noise
issue remain?

3. Substitute known-good optical
drive. Does noise issue remain?

4. Compare system with similar
model for optical drive noise in
operation and verify that noise
level is similar.

Yes Go to step 2.

No Issue due to unbalanced

media. Recommend using
dierent media.

Yes Go to step 3.

No Issue resolved by reseating

drive.

Yes Go to step 4.

No Replace optical drive. J04

Yes Noise level of optical

drive appears to be within
specication. Return
computer to user.

No Check for other causes of

noise in the computer.

2011-08-29

iMac (27-inch, Mid 2011) Symptom Charts — Mass Storage 81

SD Memory Card Cannot Be Inserted Into Slot

Unlikely cause: LCD panel, logic board, optical drive, hard drive

Quick Check

Symptom Quick Check

SD Memory Card Cannot Be
Inserted Into Slot

• SD memory card does not fully
seat into slot

• Card slot does not align with
enclosure.

1. Check that user’s SD card is not warped or
damaged, and its metal contacts are clean, intact
and free of contamination.

2. Verify that SD card is the correct size. Card
dimensions should be 32mm x 24mm x 2.1mm.
Cards thicker than 2.1mm are too thick and may
damage the card slot if inserted. Thinner cards
such as MultiMediaCards (MMC) are acceptable.
Refer to Apple Support article HT3553: About

the SD and SDXC card slot.

3. Verify that computer’s SD card slot is not

obstructed in any way. Use a ashlight to look
into the slot to make sure nothing is already
inserted. If so, carefully remove obstruction from
slot. Try to insert SD card again.

Deep Dive

Check Result Action Code

1. Verify if known-good SD card

ts in slot.

Yes Ask user to replace defective

or out-of-spec SD card.

2011-08-29

2. Verify if known-good SD card
now ts in slot.

3. Verify if SD card now ejects and
inserts without issue.

No Loosen the SD board screws,

then insert known-good SD
card again. Go to step 2.

Yes Tighten SD reader board

screws. Go to step 3.

No Replace SD card reader, retest. X24

Yes Issue resolved by SD card

reader alignment.

No Replace SD card reader. X24

iMac (27-inch, Mid 2011) Symptom Charts — Mass Storage 82

SD Memory Card Not Recognized

Unlikely cause: LCD panel, logic board, optical drive, hard drive

Quick Check

Symptom Quick Check

SD Card Not Recognized

• Card does not show up
on desktop or in System
Information (System Proler in
Snow Leopard)

1. Make sure SD card is unlocked.

2. Check that user’s SD card is not warped or

damaged, and its metal contacts are clean, intact
and free of contamination.

3. Verify that SD card slot in computer is not
damaged or obstructed in any way. Use a
ashlight to look into the slot to make sure
nothing is already inserted. If so, carefully remove
obstruction from slot. Try to insert SD card again.

4. Check for compatible SD card type and format:

• Only Standard SD (Secure Digital), SDHC (Secure
Digital High Capacity) and MultiMediaCards
(MMC) are supported. See Apple Support article
HT3553: About the SD slot. Card dimensions
should be 32mm x 24mm x 2.1mm. Cards thicker
than 2.1mm are too thick and may damage the
card slot if inserted.

• While SDIO (Secure Digital Input Output) cards t
into and shouldn’t damage card slot, they are not
supported. SDXC cards are also unsupported.

• Fat 32 formatted SD cards are limited to 4GB.
ExFAT formatted SD cards require OS X 10.6.5 or
later.

• MiniSD and Micro SD cards require adapters.

2011-08-29

5. For a more specic SD card type or format
(Wireless-enabled SD card, other SD card) make
sure that the correct driver is installed. OS X
supports only standard SD memory cards; other
cards may require specic driver software.

Deep Dive

Check Result Action Code

1. Verify if SD card inserts

correctly in SD slot.

Yes Go to step 2.

No Go to SD Memory Card

Cannot Be Inserted Into Slot.

iMac (27-inch, Mid 2011) Symptom Charts — Mass Storage 83

2. Unlock and insert user’s SD
card and verify it shows up
on desktop or in System
Information (System Proler in
Snow Leopard).

Yes Go to step 6.

No Go to step 3.

3. Insert a known-good unlocked
SD card and verify if read/write
capabilities are working.

4. Run System Information
(System Proler in Snow
Leopard) and verify if SD card
reader is now listed in USB
devices.

5. Verify if a known-good
unlocked SD card can now be
correctly read and written.

6. Lock the user’s SD card and
verify if it can’t be written.

Yes User’s SD card not functioning

properly. Contact card
manufacturer for support.

No Go to step 4.

Yes Go to step 5.

No Reseat SD cable at SD card

reader and logic board

If issue persists, replace
SD cable.

If issue persists after cable
was replaced, replace
SD card reader.

If issue persists after card
reader was replaced, replace
logic board.

Yes Go to step 6.

No Replace SD card reader. X24

Yes Issue resolved.

No Replace SD card reader. M17

X03

X24

M17

2011-08-29

Uncategorized Symptoms

Check Result Action Code

1. Verify if existing symptom code

applies to issue reported by
user.

Yes Jump to appropriate

symptom code ow.

No

iMac (27-inch, Mid 2011) Symptom Charts — Mass Storage 84

Document reported failure
and send feedback to

[e-mail]

stating that a suitable
symptom code wasn’t found.
Provide as much detail as
possible.

N99

Communications

AirPort Issues

Quick Check

Symptoms Quick Check

AirPort Issues

• Unable to nd or connect to
wireless networks

• Slow or stalled data transfers

• Intermittent connection
dropouts

• AirPort cannot be enabled

• AirPort card not available or
recognized

Check on user’s computer:

1. Verify that AirPort is turned ON, and make sure

that a network is selected.

2. Use System Information (System Proler in
Snow Leopard) to verify that installed AirPort
card supports the channel number used by the
wireless access point.

3. Check for nearby sources of interference such as
microwave ovens or cordless phones. See Apple
Support article HT1365: AirPort and Bluetooth:

Potential sources of wireless interference.

4. Check the number of users trying to use AirPort

in the area for possible network congestion
(available bandwidth).

5. Check Apple Support article HT1159: OS X

versions (builds) for computers to make sure

system build is correct for this computer model.

6. Check for and apply the latest software and
rmware updates.

7. Isolate OS by starting up from known-good
original system media or an up-to-date, bootable
OS X volume, a same-model computer in Target
Disk Mode, or compatible known-good OS on
an external drive. Both AirPort and Bluetooth
services are available when booted from Install
disc.

2011-08-29

8. In System Preferences > Sharing > Internet
Sharing, congure a known-good computer to
share its Ethernet connection to computers using
AirPort. Try to connect user’s computer to the
newly created wireless network.

(continued on next page)

iMac (27-inch, Mid 2011) Symptom Charts — Communications 85

9. Using known-good OS & base station, compare
AirPort throughput to a similar system using
Activity Monitor > Network.

10. Reset PRAM by holding down Command-Option­P-R keys while rebooting, until you hear the
startup sound for the second time.

11. Reset SMC.

If issue cannot be reproduced, recommend user
check his/her wireless base station:

1. Check for base station rmware updates.

2. Check for nearby interference sources in the

2.4/5GHz range such as microwave ovens and
cordless phones. See Apple Support article

HT1365: AirPort and Bluetooth: Potential
sources of wireless interference.

3. Check that the base station is not using MAC

address ltering or creating a hidden network.

4. Check that the base station is not set to low­power transmission mode.

5. Check that the base station is not using
unsupported connection and encryption
protocols.

6. Check for Wi-Fi channel overlap (a nearby base
station using an adjacent channel).

7. Connect to a known-good test network.

8. Test in a dierent environment.

Also see Apple Support article

HT1401: AirPort troubleshooting guide.

2011-08-29

iMac (27-inch, Mid 2011) Symptom Charts — Communications 86

Deep Dive

Check Result Action Code

1. Go to System Information

(System Proler in Snow
Leopard) > Network and verify
if AirPort is recognized.

2. Wait at least 15 seconds after
computer has been shutdown
and reseat AirPort card
connection on logic board.
Verify if AirPort card is now
listed in System Information
(System Proler in Snow
Leopard).

3. After AirPort card has been
replaced, verify if AirPort
card is now listed in System
Information (System Proler in
Snow Leopard).

4. Enable AirPort and verify if
known local AirPort networks
are available, or create a
computer-to-computer
network with another
Macintosh computer using
AirPort. See http://docs.

info.apple.com/article.
html?path=AirPort/5.0/en/
ap2110.html. Verify if you

connect successfully.

Yes Install all available software

updates for AirPort and retest.
If issue persists after software
update, go to step 4.

No Go to step 2.

Yes Issue resolved by reseating

AirPort card.

No Wait at least 15 seconds after

computer has been shutdown
and replace AirPort card and
retest. Go to step 3.

Yes Issue resolved by replacing

AirPort card.

No Replace logic board. Retest. M11

Yes Issue resolved.

No Go to step 5.

N01

2011-08-29

5. Check and reseat the two
antennas to the AirPort card.
Verify if you can connect to
known AirPort network.

Yes Issue resolved.

No Replace AirPort card. If issue

persists, replace AirPort
antenna(s). If the damaged
antenna is embedded in rear
housing behind Apple logo,
replace rear housing.

iMac (27-inch, Mid 2011) Symptom Charts — Communications 87

N04

X03

Bluetooth Issues

Quick Check

Symptoms Quick Check

Bluetooth Issues

• Computer won’t pair with
Bluetooth keyboard, mouse or
trackpad

• Slow or stalled data transfers
over Bluetooth connection

• Intermittent Bluetooth
connection dropouts

1. In System Preferences, make sure Bluetooth is on
and set to Discoverable.

2. Install fresh or charged batteries in the Bluetooth
device.

3. Move computer and Bluetooth device closer
together.

4. Attempt to pair computer with a known-good
Bluetooth keyboard or mouse.

5. Verify user’s Bluetooth device with a known-good
computer, using Apple Support article TS3048:

Troubleshooting wireless mouse and keyboard
issues.

6. Reset Bluetooth device or delete pairing (if

applicable).

7. Check Apple Support article HT1159: OS X

versions (builds) for computers to make sure

system build is correct for this computer model.

8. Check for and apply the latest software and
rmware updates.

9. If Bluetooth pairs normally at your service
location, research potential sources of
interference in the user’s environment, such
as microwave ovens or cordless phones in the

2.4/5GHz range. See Apple Support article

HT1365: AirPort and Bluetooth: Potential
sources of wireless interference.

2011-08-29

10. Isolate OS by starting up from known-good
original system media or an up-to-date, bootable
OS X volume, a same-model computer in Target
Disk Mode, or compatible known-good OS on
an external drive. Both AirPort and Bluetooth
services are available when booted from Install
disc.

iMac (27-inch, Mid 2011) Symptom Charts — Communications 88

Deep Dive

Check Result Action Code

1. Verify that computer and

known-good Bluetooth device
are both in discoverable
mode. Verify if you can now
successfully and reliably pair
the device.

2. Retest with new Bluetooth
antenna and verify if Bluetooth
issues are resolved.

3. Retest with new Bluetooth
cable/card and verify if
Bluetooth issues are resolved.

Yes Issue resolved.

No If Bluetooth cannot be

enabled, replace Bluetooth/
camera cable. If issue persists
replace Bluetooth board and
retest. Go to step 3.

If Bluetooth can be enabled
but Bluetooth communication
persists, replace Bluetooth
antenna. Go to step 2.

Yes Issue resolved.

No Replace Bluetooth board. N15

Yes Issue resolved.

No Replace logic board. M11

X03

N15

X03

2011-08-29

iMac (27-inch, Mid 2011) Symptom Charts — Communications 89

AirPort Card Kernel Panic

Quick Check

Symptoms Quick Check

AirPort Card Kernel Panic

• Kernel panic on startup

• Kernel panic or freezing while
attempting to connect to Wi-Fi
networks

• Kernel panic while transferring
data on Wi-Fi networks

1. Isolate OS by starting up from original Install
media for this computer, a same-model computer
in Target Disk Mode, or compatible known-good
OS on an external drive. AirPort and Bluetooth
services are available when booted from the
Install disk.

2. Check for and apply the latest software and
rmware updates.

Deep Dive

Check Result Action Code

1. Wait at least 15 seconds after

computer has been shutdown
before disconnecting AirPort
card from logic board. Verify if
computer now starts without
kernel panic.

Yes Reseat AirPort card and retest.

If problem continues replace
AirPort card. Go to step 2.

No Kernel panic not related

to AirPort. Restart from
Install DVD or known-good
bootable external drive and
check Panic.Log le on user’s
hard drive to nd out which
is the crashing I/O interface.
Also troubleshoot installed OS
X software.

2011-08-29

2. With replacement AirPort card
installed, verify if computer
starts now without kernel
panic.

Yes AirPort card issue. Issue

resolved.

No Replace logic board. M11

iMac (27-inch, Mid 2011) Symptom Charts — Communications 90

N13

Ethernet Issues

Unlikely cause: LCD panel, power supply, hard drive, optical drive, fans

Quick Check

Symptoms Quick Check

Ethernet Issues

• No Ethernet device present

• Unable to access network
resources

• Ethernet device shows no
connection

• Ethernet device unable to an IP
address

• Slow network performance

1. Check Ethernet cable for damage. Try a
known good Ethernet cable – CAT5 or better
recommended for 100Mbps+ connections.

2. Check Ethernet ports on the computer and wall/
switch for dust, debris, damage or bent pins.

3. Ensure distance from networking infrastructure is
less than 300 feet/ 105 meters.

4. Verify port, cable and network hardware with a
known good system. Isolate rewall, MAC address
ltering or hardware access control devices.

5. Isolate OS by starting up from original Install
media for this computer, a same-model computer
in Target Disk Mode, or compatible known-good
OS on an external drive.

6. Using known-good network hardware and cable,
start up from known-good OS X volume. Go to
Network Utility > Info and verify that the Link
Status is “Active.”

7. Check network settings. If a known-good DHCP
server is available, set System Preferences >
Network > Ethernet to “Using DHCP” and verify IP
address. (If it starts with 169.x.x.x, the system was
unable to get a valid IP address.)

2011-08-29

8. When started from user’s OS, revert to default
network settings by creating a new location in
System Preferences > Network.

iMac (27-inch, Mid 2011) Symptom Charts — Communications 91

Deep Dive

Check Result Action Code

1. Visually inspect Ethernet port

of computer and ensure that all
pins will make physical contact
with the Ethernet cable.

2. Boot from original Install media.
Verify Network Link status is
active by using Network Utility
under the “Info” tab. Verify if the
Link Status is “Active”.

3. Connect computer to another
Mac using CAT5 Ethernet
cable. See article http://

docs.info.apple.com/article.
html?path=Mac/10.6/en/8429.
html. Verify if you connect

successfully.

4. Check for speed and duplex
issues on network. Open
System Preference > Network;
click the Advanced button,
then the Ethernet tab. Verify if
the speed and duplex reported
are what is expected.

Yes Go to step 2.

No Pins are damaged, bent at or

missing. Replace logic board.

Yes Go to step 3.

No If same Ethernet cable gives

an “Active” link status on a
known-good, same-model
computer, replace logic board.

Yes Ethernet communication

good. Go to step 4.

No If same Ethernet cable and

computer connects to a
known-good, same-model
computer, replace logic board.

Yes Go to step 5.

No

Change speed and duplex
settings. See article http://

docs.info.apple.com/article.
html?path=Mac/10.6/
en/8711.html. Go to step 6.

M24

M10

M10

5. Check for MTU (Maximum

Transmission Unit) issues.
See Apple Support article

HT2532: OS X 10.4 or later:
How to change the MTU for
troubleshooting purposes.

Verify if changing MTU settings
on computer resolves issue.

6. If changing speed, duplex
or MTU settings allows
connectivity, check with a
known-good, same-model
computer. Verify if known-good
computer produces the same
results.

Yes Go to step 6.

No Ethernet controller damaged.

Replace logic board.

Yes Check with ISP or Network

Administrator concerning
speed, duplex & MTU settings.

No Verify with known good OS.

If issue persists, replace logic
board.

M10

M10

2011-08-29

iMac (27-inch, Mid 2011) Symptom Charts — Communications 92

Wireless Input Device Does Not Pair

Quick Check

Symptoms Quick Check

Wireless Input Device Doesn’t
Pair

• Computer does not recognize a
Bluetooth keyboard, mouse or
trackpad

1. Restart computer.

2. Check computer with a known-good Bluetooth

input device to test computer side.

3. Test Bluetooth device side with a known-good,
up-to-date computer with installed Bluetooth
device driver.

4. Ensure that device is being used within 30-foot
range for Bluetooth devices.

5. See Apple Support article TS3048:

Troubleshooting wireless mouse and keyboard
issues.

Deep Dive

Check Result Action Code

1. Without any wired input

devices connected, and
with a known-good Apple
wireless mouse /trackpad in
discoverable mode, startup the
computer. Verify if computer
shows the Bluetooth Mouse
Setup Assistant.

Yes Bluetooth hardware is active.

Go to step 6.

No Go to step 2.

2011-08-29

2. Connect a wired mouse
and run System Information
(System Proler in Snow
Leopard). Verify if Bluetooth
interface is listed under USB in
System Information (System
Proler in Snow Leopard).

3. Using an externally connected
display, run System Information
(System Proler in Snow
Leopard) and verify if Bluetooth
interface is listed under USB in
System Information (System
Proler in Snow Leopard).

Yes Bluetooth hardware is

present. Go to step 6.

No Remove glass and LCD panel,

reseat both ends of cable
between Bluetooth board and
logic board. Go to step 3.

Yes Bluetooth hardware is now

present. Go to step 6.

No Replace Bluetooth cable.

Go to step 4.

iMac (27-inch, Mid 2011) Symptom Charts — Communications 93

X03

4. Run System Information

(System Proler in Snow
Leopard). Verify if Bluetooth
interface is listed under USB in
System Information (System
Proler in Snow Leopard).

Yes Bluetooth hardware is now

present. Go to step 6.

No Replace Bluetooth board.

Go to step 5.

N15

5. Run System Information

(System Proler in Snow
Leopard). Verify if Bluetooth
interface is listed under USB in
System Information (System
Proler in Snow Leopard).

6. Run Software Update and
apply any available Bluetooth
updates. Activate Bluetooth
in System Preferences (or
Apple menu icon) then select
“Congure a new Bluetooth
device” (or run Bluetooth
Mouse Setup Assistant). Verify
if a known-good Bluetooth
mouse/trackpad is seen.

7. With a known-good Apple
Wireless mouse/trackpad on
and in discoverable mode,
verify if you can successfully
pair the device with the
assistant.

Yes Bluetooth hardware is now

present. Go to step 6.

No Replace logic board. M11

Yes Bluetooth discovery is now

active. Go to step 7.

No Replace Bluetooth antenna. X03

Yes Check for stability.

Go to step 8.

No Go to Wireless Input Device

Loses Connection.

2011-08-29

8. With known-good Apple
Wireless mouse/trackpad
paired, verify if the device stays
connected.

9. With user’s mouse/trackpad
paired, verify if the mouse stays
connected.

Yes Issue resolved.

No Inspect and reseat Bluetooth

antenna cable. Replace a
damaged antenna cable, or
Bluetooth board if its antenna
connector is damaged.

X03

Go to step 9.

Yes Antenna issue. Issue resolved.

Resassemble system.

No Go to Wireless Input Device

Loses Connection.

iMac (27-inch, Mid 2011) Symptom Charts — Communications 94

Uncategorized Symptoms

Quick Check

Symptoms Quick Check

Uncategorized Symptoms

• Unable to locate appropriate
symptom code.

1. Verify System Preferences/Network settings
are congured appropriately to support
communication method.

2. For Ethernet connection issues verify that cable
being used functions when used with another
known-good system.

3. For wireless connection issues review user
environment to determine whether possible
interference from other 2.4GHz communications
devices might be contributing to issue. See
Apple Support article HT1365: AirPort and

Bluetooth: Potential sources of wireless
interference.

Deep Dive

Check Result Action Code

1. Verify if existing symptom code

applies to issue reported by
user.

Yes Jump to appropriate

symptom code ow.

No

Document reported failure
and send feedback to

[e-mail]

stating that a suitable
symptom code wasn’t found.
Provide as much detail as
possible.

N99

2011-08-29

iMac (27-inch, Mid 2011) Symptom Charts — Communications 95

Input/Output Devices

Thunderbolt Not Recognized

Unlikely cause: LCD panel, hard drive, optical drive, fans

Quick Check

Symptoms Quick Check

Thunderbolt Not Recognized

• Thunderbolt hardware not
listed in System Information
(System Proler in Snow
Leopard).

1. Check Apple Support article HT1159: OS X

versions (builds) for computers to make sure

system build is correct for this computer model.

2. Check for and apply the latest software and
rmware updates.

3. Verify in System Information (System Proler in
Snow Leopard) that Thunderbolt hardware is
present.

Deep Dive

Check Result Action Code

1. Check Apple support article

HT1159: OS X versions (builds)
for computers to make sure

system build is correct for
this computer model. Is OS X
version equal to or a newer
than a version that will support
Thunderbolt functionality?

Yes Go to step 2.

No Restore system from media

shipped with product.
Note: Always use product­specic restore media. Retail
versions of the same OS may
not have specic drivers to
support this model.
Check for and apply the
latest software and rmware
updates. Go to step 2.

2011-08-29

2. Check for and apply the
latest software and rmware
updates. Verify in System
Information (System Proler
in Snow Leopard) that
Thunderbolt hardware is
present, listing a unique UID
number and latest revisions
for controller and port micro
rmware.

Yes Issue resolved.

No Go to step 3.

iMac (27-inch, Mid 2011) Symptom Charts — Input/Output Devices 96

3. Reset PRAM by holding down
Command-Option-P-R keys
while rebooting, until you
hear the startup sound for
the second time. Verify in
System Information (System
Proler in Snow Leopard)
that Thunderbolt hardware is
present.

Yes Issue resolved.

No Replace logic board.

Thunderbolt Target Disk Mode Issues

Unlikely cause: LCD panel, hard drive, optical drive, fans

Quick Check

Symptoms Quick Check

Thunderbolt Target Disk Mode
Issues

• Thunderbolt hardware is
present in System Information
(System Proler in Snow
Leopard) and Port Status does
not show a connection to
attached Target Disk Mode
computer.

• Target Disk Mode computer will
not mount to user’s desktop.

1. Check Apple Support article HT1159: OS X

versions (builds) for computers to make sure

system build is correct for this computer model.

2. Check for and apply the latest software and
rmware updates.

3. Check if attached Thunderbolt device is listed
in System Information (System Proler in Snow
Leopard) > Hardware > Thunderbolt.

4. Substitute a known-good Thunderbolt to
Thunderbolt cable.

Deep Dive

Check Result Action Code

1. Check Apple support article

HT1159: OS X versions (builds)
for computers to make sure

system build is correct for
this computer model. Is OS X
version equal to or a newer
than a version that will support
Thunderbolt functionality?

Yes Go to step 2.

No Restore system from media

shipped with product.
Note: Always use product­specic restore media. Retail
versions of the same OS may
not have specic drivers to
support this model.
Check for and apply the
latest software and rmware
updates. Go to step 2.

2011-08-29

iMac (27-inch, Mid 2011) Symptom Charts — Input/Output Devices 97

2. Start up a known-good,
Thunderbolt-capable computer
in Target Disk Mode (TDM) by
holding the T key at startup
until display shows Thunderbolt
and FireWire icons. Reseat
Thunderbolt cable on both
TDM computer and user’s
computer.

Start up user’s computer and
verify that TDM computer’s
hard drive has mounted on
desktop of user’s computer.

Yes Go to step 3.

No Go to step 4.

3. Verify Thunderbolt connection
by copying a le from TDM
computer to user’s computer.
Note: File transfer speed is
limited by internal hard drive
limit of 3 Gbits/second.

Are you able to copy a le
across the Thunderbolt
connection?

4. Disconnect all connections
to Thunderbolt port on user’s
computer. Check for and
apply the latest software and
rmware updates. Verify in
System Information (System
Proler in Snow Leopard)
that Thunderbolt hardware is
present, listing a unique UID
number and latest revisions
for controller and port micro
rmware.

5. Inspect both connector ends
of Thunderbolt cable for
cable/connector damage,
then inspect wire for cuts,
pulled strain relief or broken
connector housing. Has
Thunderbolt to Thunderbolt
cable (2 m) sustained any
damage that would aect
connectivity?

Yes Issue resolved.

No Go to step 4.

Yes Go to step 5.

No Replace logic board. M33

Yes Replace Thunderbolt to

X26

Thunderbolt cable.

No Go to step 6.

2011-08-29

iMac (27-inch, Mid 2011) Symptom Charts — Input/Output Devices 98

6. Inspect Thunderbolt port on
user’s computer for physical
damage or possible burn
mark indicators suggesting
a defective port. Does
Thunderbolt port appear to be
damaged?

Yes Replace logic board. M24

No Go to step 7.

7. Check Thunderbolt cable
connector alignment with port
opening. Can the Thunderbolt
cable be inserted into the port
fully without interference or
excessive force to seat it fully?

8. Test user’s computer with a
known-good Thunderbolt
to Thunderbolt cable. Does

Thunderbolt port establish a
TDM connection to a known­good, Thunderbolt-capable
computer with the known­good Thunderbolt cable?

9. Test user’s computer with
user’s Thunderbolt to
Thunderbolt cable. Does

Thunderbolt port establish
a TDM connection to a
known-good, Thunderbolt­capable computer with user’s
Thunderbolt cable?

Yes Go to step 8.

No Logic board misaligned with

port opening in rear housing.
Realign logic board to rear
housing.

If Thunderbolt port shows
signs of damage which make
proper alignment impossible,

M24

replace logic board.

Yes Go to step 9.

No Replace logic board. M33

Yes Issue resolved.

No Replace Thunderbolt to

X26

Thunderbolt cable.

2011-08-29

iMac (27-inch, Mid 2011) Symptom Charts — Input/Output Devices 99

Thunderbolt Target Display Mode Issues

Unlikely cause: LCD panel, hard drive, optical drive, fans

Quick Check

Symptoms Quick Check

Thunderbolt Target Display
Mode Issues

• Unable to activate remote
computer to be target display
for user’s computer.

• Unable to activate user’s
computer to be target display
for a remote computer.

1. Note: Internal display of Mac portables are
prohibited from being set to Target Display Mode.

2. Check Apple Support article HT1159: OS X

versions (builds) for computers to make sure

system build is correct for this computer model.

3. Check for and apply the latest software and
rmware updates.

4. Verify in System Information (System Proler in
Snow Leopard) that Thunderbolt hardware and
any connected devices are present.

5. Substitute a known-good Thunderbolt to
Thunderbolt cable.

6. Do not use the Apple Pro Keyboard; use only
newer keyboards.

Deep Dive

Check Result Action Code

1. Check Apple support article

HT1159: OS X versions (builds)
for computers to make sure

system build is correct for
this computer model. Is OS X
version equal to or a newer
than a version that will support
Thunderbolt functionality?

Yes Go to step 2.

No Restore system from media

shipped with product.
Note: Always use product­specic restore media. Retail
versions of the same OS may
not have specic drivers to
support this model.
Check for and apply the
latest software and rmware
updates. Go to step 2.

2011-08-29

iMac (27-inch, Mid 2011) Symptom Charts — Input/Output Devices 100