Apple iMac 21 mid 2010 Service Manual
Apple Technician Guide
iMac (21.5-inch, Mid 2010)
Updated: 2010-09-03
Apple Inc.
© 2010 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 eort has been made to ensure that the information in this document is accurate. Apple
is not responsible for printing or clerical errors.
Apple
1 Innite 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 (21.5-inch, Mid 2010)
Contents
About This Guide
Updates 9
Updated 3 September 2010 9
Apple Technician Guide introduced 27 July 2010 9
Feedback 9
Basics
Overview 11
Identifying Features 12
Product Congurations 12
Safety Precautions 13
Serial Number Location 14
New Accessories 15
Magic Trackpad 15
Apple Battery Charger 17
Troubleshooting
General Troubleshooting 19
Wireless Troubleshooting 19
Update System Software & Firmware 19
Troubleshooting Theory 19
Hardware vs. Software 19
Common Reset Procedures 20
Power On Self Test (POST) 20
Resetting the System Management Controller (SMC) 20
Resetting Parameter RAM (PRAM) 21
Starting Up in Safe Mode 21
Removing the Battery, Measuring DC Voltage 22
Diagnostics 23
Sensor and Fan Connector Locations 25
Diagnostic LEDs 26
LED Startup Sequence 27
Logic Board Test Points 28
Block Diagram 29
Functional Overview 30
Symptom Charts 31
Startup and Power 31
No Power, Dead Unit 31
Won’t Start Up 33
Intermittent Shutdown 35
Troubleshooting Shutdown Causes 35
Kernel Panic, System Crashes 39
No Video 41
Corrupted Video 43
Burnt Smell/Odor 46
Uncategorized Symptoms 47
Display 48
Backlight Issue/No Backlight 48
Noise / Unstable Flickering 50
LCD Image Issues 52
Incorrect/Missing Colors 53
Distorted/Blurred Image 54
Pixel Anomalies 56
Vertical/Horizontal Lines 57
Non-Uniform Brightness 59
Cosmetic Defects 60
Uncategorized Symptoms 60
Mass Storage 61
Hard Drive Not Recognized 61
Optical Drive Not Recognized 67
Optical Drive Won’t Accept/Eject Media 68
Optical Drive Read/Write Error 70
Optical Drive Not Performing to Specications 72
Optical Drive Noisy 73
SD Card Will Not Insert Into Slot 74
SD Card Not Recognized 75
Uncategorized Symptoms 76
Communications 77
AirPort/Bluetooth Issues 77
AirPort Card Kernel Panic 80
Ethernet Port/Device Issue 81
Wireless Input Device Doesn’t Pair 82
Uncategorized Symptoms 84
Input/Output Devices 85
Apple Remote Inoperable 85
Audio: Microphone 87
Audio: Built-in Speakers Have Distorted Sound 88
Audio: Built-in Speakers Have No Sound 89
Camera Issues 91
FireWire Device Not Recognized 92
USB Device Not Recognized 94
Wired Keyboard Does Not Function Properly 96
Keyboard: Specic Keys Do Not Respond 98
Wired Keyboard/Mouse Not Recognized 98
Wireless Input Device Does Not Pair 100
Apple Wireless Mouse/Magic Trackpad Erratic Tracking 102
Wireless Input Device Loses Connection 103
Mechanical 107
Noise/Hum/Vibration 107
Fan Failures / Thermal Issues 110
Stand/Hinge Issues 111
Physical Damage 112
Uncategorized Symptoms 112
Take Apart
General Information 114
Opening the Unit 114
Required Tools 114
Required Special Tools for Glass Panel 115
Cleaning Tools Starter Kit 115
Cleaning & Handling the Glass Panel 116
Do’s and Don’ts 116
Handling a Broken Glass Panel 116
How to Remove a Broken Glass Panel 117
Safety 121
Logic Board Handling 122
Note About Images in This Guide 122
Access Door 123
Memory 125
Glass Panel 127
Removal 128
Reassembly 129
LCD Panel 132
Handling LCD Panel 136
DisplayPort Cable 138
Vertical Sync (V-Sync) Cable 140
LCD Temp Sensor Cable 141
Bluetooth Board 142
Bluetooth Antenna 144
Camera 146
AirPort Antenna 149
AirPort Card 151
LED Backlight Board 153
Power Supply 155
Backlight Pressure Wall 157
Power Supply Pressure Wall 159
Hard Drive 161
Hard Drive Sensor Cable 164
Bluetooth/Camera/Sensor Cable 166
Optical Drive 170
Optical Drive Sensor Cable 172
Optical Drive Fan 173
SD Card Reader 175
SD Card Reader Cable 178
IR Board & Cable 180
Logic Board 182
Video Card 189
Video Card Bracket 191
Battery 193
Audio Cable 195
Hard Drive Data Cable 198
Optical Drive Data Cable 201
Cable, AC/DC/SATA/Backlight Power 203
CPU Fan 204
Left Speaker 207
Right Speaker 209
Hard Drive Fan 211
Optical Drive Pressure Wall 213
Mechanism Cover 215
Stand 217
Mechanism 219
Rear Housing 221
Views
Exploded Views 225
iMac (21.5-inch, Mid 2010), Part 1 225
iMac (21.5-inch, Mid 2010), Part 2 226
iMac (21.5-inch, Mid 2010), Part 3 227
Screw Chart 228
External Views 230
Front View 230
Rear View 231
I/O Ports 232
Internal Views 233
Photo of Components below LCD 233
Photo of Components below Logic Board 234
Logic Board, Front Side 235
Logic Board, Back Side 235
Apple Technician Guide
About This Guide
iMac (21.5-inch, Mid 2010)
© 2010 Apple Inc. All rights reserved.
Updates
Updated 3 September 2010
Basics:
• Overview: New Accessories: Magic Trackpad and Apple Battery Charger: Added links to the
User Guides.
Troubleshooting:
• Display: several symptoms: Modied steps to allow unit to warm up for about a minute
(instead of 15 minutes) before evaluating front-of-screen performance.
Take Apart:
• LCD Panel: Added note that overtightening screws could lead to issue of light leakage after
unit is reassembled.
• Camera and Rear Housing: Added note that white thermal paste intended for camera
should not be used for any other purpose (such as portable computer heatsinks).
Views:
• Screw Chart: Added image for screw 922-7018.
Apple Technician Guide introduced 27 July 2010
Feedback
We want your feedback to help improve this and future Technician Guides!
Please email any comments to: smfeedback6@apple.com
2010-09-03
iMac (21.5-inch, Mid 2010) — Updates 9
Apple Technician Guide
Basics
iMac (21.5-inch, Mid 2010)
© 2010 Apple Inc. All rights reserved.
Overview
2010-09-03
The iMac (21.5-inch, Mid 2010) 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 identical to the previous
model, iMac (21.5-inch, Late 2009), but includes new options such as faster Intel Core i3 and i5
processors with speeds up to 3.6GHz, better graphics, and an additional input device option,
the Apple Magic Trackpad.
The Mid 2010 model can be most easily distinguished from the Late 2009 model by the internal
position of the AirPort card, which now connects directly to the logic board in the center of the
unit.
iMac (21.5-inch, Mid 2010) Basics — Overview 11
Identifying Features
The iMac (21.5-inch, Mid 2010) features include:
• Built-in 21.5-inch (viewable) LED-backlit glossy widescreen TFT active-matrix liquid crystal
display with IPS technology; 1920 by 1080 pixel resolution
• Processor and memory:
• 3.06GHz Intel Core i3 with 4MB level 3 cache
• 3.2GHz Intel Core i3 with 4MB level 3 cache
• 3.6GHz Intel Core i5 with 4MB level 3 cache (CTO)
• 4GB (two 2GB SO-DIMMs) of 1333MHz DDR3 SDRAM; four SO-DIMM slots support up to
16GB maximum
• Graphics and video support:
• ATI Radeon HD 4670 with 256MB of GDDR3 memory
• ATI Radeon HD 5670 with 512MB of GDDR3 memory
• Mini DisplayPort output with support for DVI, VGA, and dual-link DVI (adapters sold
separately)
• 500GB, 1TB, or 2TB 7200-rpm 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 10.6.3
• Apple Magic Mouse (2010) and Apple Wireless Keyboard (2009) standard with all
congurations
• Apple Magic Trackpad (CTO)
• Apple Battery Charger (CTO)
Product Congurations
For product congurations, refer to AppleCare Tech Specs: http://support.apple.com/specs/
2010-09-03
iMac (21.5-inch, Mid 2010) Basics — Overview 12
Safety Precautions
Warning: HIGH VOLTAGE: The AC/DC power supply PCB remains powered up whenever
system is plugged in, whether or not system has been turned on. Use extreme caution
when troubleshooting system with the glass panel removed.
Important: If computer is shut down by removing power cord, allow power supply a good 2-3
minutes to discharge capacitors before handling it. However, if you select “Shut Down” via the
Apple menu, the computer will discharge power supply capacitor almost immediately.
2010-09-03
iMac (21.5-inch, Mid 2010) Basics — Safety Precautions 13
Serial Number Location
The iMac (21.5-inch, Mid 2010)’s serial number is located on the bottom of the stand. When
replacing a stand, transfer the serial number to the new stand.
2010-09-03
iMac (21.5-inch, Mid 2010) Basics — Serial Number Location 14
New Accessories
Magic Trackpad
The wireless Magic Trackpad uses Bluetooth technology to connect to the Mac and comes with
two AA batteries installed. To use the Magic Trackpad and its full features, update your Mac to
Mac OS X version 10.6.4 or later, and then install the latest trackpad software using Software
Update, if needed. For more information, refer to the Magic Trackpad User Guide.
Note: If the iMac (21.5-inch, Mid 2010) has had system software reinstalled for any reason, pair
the Magic Trackpad and then run Software Update. If only basic functionality is present on
Magic Trackpad, ensure that it is paired correctly before launching Software Update. For more
information, refer to:
• kBase #HT4254: About Magic Trackpad and Multi-Touch Trackpad Update 1.0
• kBase #HT4273: About Magic Trackpad Update 1.0 for Windows
About the Indicator Light
The indicator light displays the status of your Magic Trackpad and the batteries.
• When you rst turn your trackpad on, the indicator light glows steadily for 2 to 3 seconds,
indicating the batteries are good.
• If your trackpad isn’t paired with a Mac, the light blinks, indicating your trackpad is in
discovery mode and ready to pair (pairing means connecting your trackpad and Mac to
each other wirelessly).
• If you don’t pair your trackpad with your Mac within 3 minutes, the light and trackpad turn
o to conserve battery life. Press the on/o button on your trackpad to turn it on again,
allowing you to pair it with your Mac.
• When your trackpad is on and connected, the indicator light turns o.
2010-09-03
Turn on the Trackpad
• To turn the trackpad on, press rmly and release the on/o button.
• To turn the trackpad on and make it stay in discovery mode (prevent auto-pairing to
previous known host), press and hold the on/o button.
iMac (21.5-inch, Mid 2010) Basics — New Accessories 15
Pairing the Magic Trackpad
To pair your trackpad:
1. Choose Apple () menu > System Preferences, and then click Trackpad.
2. Click “Set Up Bluetooth Trackpad …” in the lower-right corner.
3. Press the on/o button on your trackpad to turn it on.
4. Click Continue when your trackpad is detected.
Once your trackpad is paired with your Mac, use Software Update again to make sure you have
the latest software installed.
Note: If the iMac (21.5-inch, Mid 2010) has had system software reinstalled for any reason, pair
the Magic Trackpad and then run Software Update. If only basic functionality is present on
Magic Trackpad, ensure that it is paired correctly before launching Software Update.
Installing Batteries
1. Use a coin to remove the battery compartment cover on the left side.
2. Insert batteries into the battery compartment as shown.
Warning: Replace or recharge batteries at the same time. Don’t mix old batteries with new
batteries and don’t mix battery types (for example, alkaline and lithium batteries). Don’t open
or puncture the batteries, install them backwards, or expose them to re, high temperatures, or
water. Don’t charge nonrechargeable AA batteries. Keep batteries out of the reach of children.
2010-09-03
iMac (21.5-inch, Mid 2010) Basics — New Accessories 16
Apple Battery Charger
Use the Apple Battery Charger to charge rechargeable NiMH batteries for your Apple products
that use AA batteries. Each Apple Battery Charger comes with six high-performance AA NiMH
batteries: two for your keyboard, two for your mouse or trackpad, and two for charging. You
can use the Apple Battery Charger to charge either one or two NiMH rechargeable batteries. To
charge batteries fully, allow at least ve hours of charging time. For more information, refer to
the Battery Charger User Guide or kBase #HT4275: About Apple Battery Charger.
Batteries
Use only NiMH rechargeable batteries in the Apple Battery Charger. Don’t try to charge
nonrechargeable AA batteries (lithium or alkaline) in the charger.
Caution: Risk of explosion if battery is replaced by an incorrect type. Dispose of used batteries
according to the instructions. Don’t open or puncture the batteries, install them backwards,
short circuit, or expose them to re, high temperatures, or water. Keep batteries out of the reach
of children.
Status Lights
The indicator light on top of the Apple Battery Charger displays the charging status of the
batteries.
• Amber: The batteries are charging.
• Green: The batteries are charged and ready to use—the green indicator light shuts o after
six hours.
• No light: May indicate any of the following conditions:
• The batteries are charged and ready to use.
• The inserted batteries are too deeply discharged to register immediately.
• Flashing Amber: May indicate any of the following conditions:
• The batteries haven’t been properly installed in the charger.
• An unsupported type of battery is in the charger.
• The batteries may be faulty or damaged and should be replaced.
2010-09-03
iMac (21.5-inch, Mid 2010) Basics — New Accessories 17
Apple Technician Guide
Troubleshooting
iMac (21.5-inch, Mid 2010)
© 2010 Apple Inc. All rights reserved.
General Troubleshooting
Wireless Troubleshooting
If you’re having issues with Bluetooth and wireless connectivity issues, refer to:
• Bluetooth Service Diagnostic (BSD) self-paced training
• Bluetooth Troubleshooting Course
• kBase #TS3048: Troubleshooting wireless mouse and keyboard issues
• kBase #HT3887: Wireless input devices: Bluetooth frequently asked questions
• kBase #HT1365: AirPort and Bluetooth: Potential source of interference
• kBase #HT3903: Apple Wireless Keyboard and Mouse: How to install batteries
• kBase #HT4275: About Apple Battery Charger
• kBase #HT4254: About Magic Trackpad and Multi-Touch Trackpad Update 1.0
• kBase #HT4273: About Magic Trackpad Update 1.0 for Windows
Update System Software & Firmware
Important: Ensure the correct version Mac OS X and latest software and rmware updates have
been applied before you begin troubleshooting. Computers sometimes exhibit symptoms that
indicate the wrong Mac OS X system software is installed.
Firmware is the name given to software that is written into memory circuits such as ash
memory, that will hold the software code indenitely, even when power is removed from
the hardware. Firmware on Intel Mac computers is designed to be updated if necessary by
running the Mac OS X Software Update check (available in the Apple menu) while computer is
connected to the Internet. For more information about rmware updates, refer to:
kBase # HT1557: About rmware updates for Intel-based Macs
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:
kBase #TS1388: Isolating issues in Mac OS X
For information on how to troubleshoot a software issue, refer to:
kBase #HT1199: Mac OS X: How to troubleshoot a software issue
kBase #TS1394: Mac OS X: Troubleshooting installation and software updates
kBase #HT2956: Troubleshooting Mac OS X installation from CD or DVD
2010-09-03
iMac (21.5-inch, Mid 2010) — General Troubleshooting 19
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-specication 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 the POST test again, remove all installed memory and test by installing one
by one each memory module that has been veried to work correctly on another system
(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:
kBase #HT2538: iMac (Mid 2007) and later models: About new startup tones
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:
1. From 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 all cables from computer, including power cord.
3. Press and hold the power button for 5 seconds.
4. Release the power button.
5. Attach the computer’s power cable, 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:
kBase #TS1433: iMac: Fans run at full speed after computer turns on
6. Press the power button to turn on the computer.
For more information, refer to:
kBase #HT1543: Intel-based iMacs: Resetting the System Management Controller (SMC)
2010-09-03
iMac (21.5-inch, Mid 2010) — General Troubleshooting 20
Resetting Parameter RAM (PRAM)
PRAM stores certain system and device settings in a location that Mac 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, P, and R. You will need to hold
these keys down simultaneously in Step 4.
Note: If the keyboard does not have an Option key, use the Alt key instead.
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:
kBase #HT1242: Mac OS X: What’s stored in PRAM
kBase #HT1379: Resetting your Mac’s PRAM and NVRAM
Starting Up in Safe Mode
A Safe Boot is a special way to start Mac 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 Mac OS X startup screen and a
gray progress bar is displayed on bottom of window (since Mac OS X 10.6).
5. To leave Safe Mode, restart computer normally, without holding down any keys during
startup.
For more information, refer to:
kBase #HT1564: Mac OS X: What is Safe Boot, Safe Mode?
kBase #TS1884: Safe Boot takes longer than normal startup
2010-09-03
iMac (21.5-inch, Mid 2010) — General Troubleshooting 21
Removing the Battery, Measuring DC Voltage
1. Shut down and unplug the computer. Allow several minutes for power supply to discharge.
2. Remove logic board.
3. Remove coin battery for 1-2 minutes. The coin battery is located on the back side of the
logic board (see graphic below).
4. Measure DC voltage on battery touching battery with red probe, and grounding with black
probe. If voltage is 2.7v or less, replace battery.
5. Reinstall the battery and logic board. This will reset the logic board.
6. Power on computer.
7. If computer boots, check for and install all software and rmware updates.
2010-09-03
iMac (21.5-inch, Mid 2010) — General Troubleshooting 22
Diagnostics
Run latest available service utilities to determine if any thermal sensors or blowers 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,
blower, logic board, video card, or power supply). See chart below for correlation between
aected 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 specic restore DVD is inserted). If a sensor error is detected, AHT will report
an error code containing the aected 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 Excessive optical drive
area temperature, or ODD
temp sensor damaged/
disconnected from logic
board.
TH00 Excessive hard drive area
temperature, or HD temp
sensor damaged/disconnected
from logic board. Use the
correct sensor cable, each
drive vendor has a unique
sensor cable model.
Tm0p Excessive logic board
temperature (this sensor is
part of logic board)
TL0p Excessive LCD panel area
temperature, or LCD temp
sensor damaged/disconnected
from top of logic board
Verify that incoming/outgoing
air vents are free from
obstruction , that CPU fan
cable is securely connected
to the left edge of the logic
board. Replace fan/sensor
assembly 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.
Verify sensor cable is securely
connected to top side of
logic board, and is correctly
connected and oriented to
the hard drive end. Check for
damaged cable or logic board.
Test with known-good logic
board
Verify that the LCD sensor
cable is securely connected
to the logic board and the
sensor is covered by a foam
gasket on the LCD.
All fans ramp
at full speed if
fan/sensor is
disconnected.
The ODD fan
will run at full
speed if sensor
is disconnected.
The HD fan may
run at full speed
if the sensor is
disconnected/
misconnected.
The CPU fan will
run at full speed
if the sensor is
disconnected.
2010-09-03
iMac (21.5-inch, Mid 2010) — General Troubleshooting 23
TS2P Excessive upper internal
enclosure temperature, or
Bluetooth/camera/sensor
damaged/disconnected from
top of logic board.
TC0H Excessive processor heatsink
temperature, or CPU temp
sensor damaged/disconnected
from logic board (this sensor is
part of logic board)
TG0D Excessive graphics processor
die temperature (sensor is part
of graphics processor chip)
TG0H Excessive graphics processor
heatsink temperature, or
GPU temp sensor damaged/
disconnected from back side
of logic board (this sensor is
part of video card assembly)
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.
Verify that the Bluetooth/
camera/sensor cable is
securely connected to the top
of the logic board. Replace
the cable if damaged.
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 video
card
Check GPU sensor cable
connection to logic board.
(requires removal of the logic
board to access).
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
assembly if the error persists.
If the sensor is
disconnected,
the CPU fan
will run at full
speed.
If sensor is
disconnected
the ODD fan
will run at full
speed.
Normal fan
operation,
except the ODD
blower
Normal fan
operation,
except the HDD
blower
Normal fan
operation,
except the CPU
blower
2010-09-03
iMac (21.5-inch, Mid 2010) — General Troubleshooting 24
Sensor and Fan Connector Locations
Temp 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,
Apple Hardware Test or Macintosh Resource Inspector diagnostics will generate an error code.
2010-09-03
iMac (21.5-inch, Mid 2010) — General Troubleshooting 25
Diagnostic LEDs
There are four built-in diagnostic LEDs on the logic board that can help troubleshoot the
computer. LEDs are located on the front center of the logic board, above the IR board, to the
left of the SMC reset button.
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 dier:
• - 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 AC cable is kept connected and AC power source is present.
Disconnecting the AC cable 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.
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.
2010-09-03
iMac (21.5-inch, Mid 2010) — General Troubleshooting 26
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.
LED Startup Sequence
LED #1 = Power available.
If no LED is visible:
• First disconnect the AC cable 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 AC cable 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
2010-09-03
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 Won’t Start Up 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
iMac (21.5-inch, Mid 2010) — General Troubleshooting 27
Logic Board Test Points
Test points, which can be used to verify proper power ow, are accessible in center of logic
board, to right of SMC Reset button, when LCD panel is removed. All voltages given in
Troubleshooting Symptom Charts assume that computer is plugged into a known-good power
outlet with a known-good AC cable. Some guidelines for using test points:
• Warning: HIGH VOLTAGE: Use extreme caution when live testing!
• Do NOT lean over or touch the power supply area during live testing.
• Keep your ngers behind nger guards on test probes when measuring.
• Turn dial of voltmeter/multimeter to measure DC (direct current, usually indicated by a solid
horizontal line over dashes). If your voltmeter requires a set voltage range, choose a DC
range that includes the voltage you are measuring.
• Connect black probe to ground. Connect red probe to test point and verify voltage.
For more info, see kBase #HT3250: Diagnostics: Using a digital multimeter
2010-09-03
Test Point Function
Pin 1 Ground
Pin 3 5V power for Hard Drive(s). Note: If present, the 12V power will come directly
from the Power Supply to the Hard Drive thru the power harness cable.
Pin 4 Standby 12V power (permanent power coming from power supply, present as
long as AC cable is connected, even if computer is o); corresponds to LED #1
Pin 6 Backlight Control pulse width modulated signal (from logic board to LED
backlight board, to adjust the backlight level setting according to user setup)
Pin 11 12V Run-Mode power to logic board (coming from power supply, present as
long as system is on or asleep); corresponds to LED #2
Pin12 Power On Request signal (from logic board to power supply when power
button is pressed)
Pin 13 Backlight Enable (signal from logic board to Backlight Controller board, to
enable backlight
iMac (21.5-inch, Mid 2010) — General Troubleshooting 28
Block Diagram
Refer to this diagram to see how modules are interrelated.
2010-09-03
iMac (21.5-inch, Mid 2010) — General Troubleshooting 29
Functional Overview
Refer to this diagram for symptoms related to logic board connectors.
To rotate this page in Preview for easier viewing, go to Tools menu and choose “Rotate Left”.
- reduced performance or system
sleep if LCD temperature gets too high
IR Receiver:
Ram:
- no boot,
- beep tones on startup,
- freezes, or kernel panics
Control + Power Supply
Temperature sensor:
- no power, no video
- no/poor backlight control
- fan runs at higher speed
- reduced performance or
system sleep if power supply
temperature gets too high
- no boot from bootable HD
- no HD visible on SATA bus
Optical Drive SATA Data +
Power:
- no boot from ODD drive
-no ODD seen on SATA bus
- ODD drive does not inject /
eject any media
high
Power Supply + Backlight
Hard Drive SATA Data :
CPU Temperature Sensor:
- fan running at higher speed,
- reduced performance or system
sleep if CPU temperature gets too
- reduced performance or system
gets over heating
sleep if CPU temperature gets too
high due to disconnnected fan/sensor
blocked fan
- no Power On (unless shorting the
pads on logic board)
startup
CPU Fan + Ambient Air
Temperature sensor:
- fan(s) running at higher speed
- system freezes or kernel panic if CPU
- no IR Remote functionality
Power On Button:
Backup Battery:
- no video
- beep sequence on
Bluetooth + Camera + Camera LED
+ Skin (enclosure) Temp Sensor:
- cannot enable Bluetooth or camera
- no LED when camera is on
- fan running at higher speed
- reduced performance or system
sleep if enclosure temperature gets too
high
LCD Temperature Sensor:
- fan running at higher speed
Hard Drive Temperature
Sensor:
- fan running at higher speed
if cable disconnected,
miscconnected, or not
matching drive brand/model
Hard Drive Fan:
- hard drive data
corruption if fan is
blocked or disconnected
Optical Drive Temperature
Sensor:
- ODD fan running at higher
- media read/burning fail if
speed
ODD temperature gets too
high
Optical Drive Fan:
- ODD temperature getting
- media read / burning fails if
too high
fan disconnected or
blocked
LCD DisplayPort:
- no video on internal LCD
- defective video on internal
Audio Board:
- no external Optical/
Analog audio input or
output
Left Speaker
- no sound from left speaker
- no SD card read
System Profiler
- no video on internal LCD and
on external DisplayPort
connector
Microphone
- no internal microphone sound
input
SD Card Reader:
- no SD card reader seen in
- distorted left sound
MXM Video Card:
Right Speaker :
- no sound from right speaker
- distorted right sound
- reduced performance or
system sleep if video card
temperature gets too high
Video Card Temperature
Sensor:
- fan running at higher speed
- video artifacts / video freezes
LCD
AirPort Card:
- cannot enable AirPort
- kernel panic (trace available in
panic.log when loading
wireless driver)
2010-09-03
iMac (21.5-inch, Mid 2010) — General Troubleshooting 30
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