Apple led cinema display 27inch User Manual

							LED Cinema Display (27-inch) Basics — Serial Number Location 11 2010-11-18
Serial Number Location
Serial Number on Stand
The LED Cinema Display (27-inch)’s serial number is located on the base of the stand. When 
replacing a stand, transfer the serial number to the new stand. 
Serial Number on Mechanism
The LED Cinema Display (27-inch)’s serial number is also located on the hinge mechanism 
inside, for users who remove the stand to use a VESA mount. When replacing a mechanism, 
transfer the serial number label to the new mechanism.  
						

							© 2010 Apple Inc. All rights reserved.
 Apple Technician Guide 
Troubleshooting
LED Cinema Display (27-inch)   
						

							LED Cinema Display (27-inch) Troubleshooting — General Troubleshooting 13 2010-11-18
General Troubleshooting
Troubleshooting Theory
For general information on troubleshooting theory, go to GSX and find the Service Training 
course menu link. From there you can access the Troubleshooting Theory self-paced course. 
Also, refer to the following Apple Knowledge Base articles: 
kBase #TS1388: Isolating issues in Mac OS X 
kBase #HT1199: Mac OS X: How to troubleshoot a software issue
Update System Software & Firmware
Important: Before beginning troubleshooting, connect the display to a known-good computer 
and ensure that the latest software and firmware updates have been installed. Some controls or 
options for the LED Cinema Display (27-inch) may not appear in System Preferences: Displays if 
incorrect system software is installed, or if the latest software and firmware updates (released at 
or after the display’s introduction) are not applied AFTER the display has been connected to an 
eligible computer.
If using a LED Cinema Display (27-inch) with Windows, run Windows Apple Software Update 
after connecting the display in order to download software that will enable functionality 
and support for Windows. If a computer is dual-booting, the display software will need to be 
installed separately for both Mac OS and Windows.
Display Adapters
Apple does not support the use of “daisy chaining” or using multiple display adapters (of 
any kind, active or passive) with any Apple displays. The list of possible symptoms observed 
by doing this are broad, however, some more common ones include not being able to use 
connected USB keyboards after waking from sleep, issues with distortion, and issues which do 
not occur when only a single adapter is used.
Check Audio Features of Connected Computer
The LED Cinema Display (27-inch) has two ways to reproduce audio coming from a computer: • Audio via the Mini DisplayPort, when computer does support this feature, and
•  Audio via the USB port, for all computer models.
Before troubleshooting an audio-related issue, first identify which computer model is used 
with the display, and which cable(s) are connected.  Computers released before 2009 will NOT 
support audio output through the Mini DisplayPort.  
						

							LED Cinema Display (27-inch) Troubleshooting — General Troubleshooting 14 2010-11-18
Functional Overview
A guide to connector locations, and the possible symptoms when the cable is disconnected, 
mis-connected or shorted.
Power Supply
No Power, no video, no 
MagSafe power, no USB 
output power, no camera 
input, no audio output, no  audio input, no fan
LCD Panel Control No video, distorted 
video, no  Audio Output  through speakers (via  DisplayPort audio), 
display brightess change (no LCD temp feedback)
Fan
Display getting hot, 
Display shutting down 
when hot, fan running at 
full speed, fan not running
Camera + Camera LED + ALS light Sensor
No Camera, no LED when 
camera is used, brightness  does not adjust to a room  light level change
Microphone
No audio input when 
display microphone is  selected in System 
Preferences Sound Input
SubWoofer
Missing low frequencies 
reproduction when display  speakers are selected in 
System Preferences Sound 
Output
Left Speakers
Missing mid & high frequency reproduction on  left side when display speakers are selected in  System Preferences Sound Output USB (from computer)
No camera 
functionality , USB 
devices connected not 
seen, no audio input 
from microphone, no 
audio output through 
speakers (via USB 
audio)
LCD LED backlight
No backlight, uneven 
backlight, flickering 
backlight
Exhaust Temp sensor
Display getting hot, fan 
not running, fan running  at full speed
Right Speakers
Missing mid & high frequency reproduction 
on right side when display speakers are 
selected in System Preferences Sound Output
USB ports (to 
connected devices)
USB devices not seen, 
No iPod/IPhone/iPad 
charge  
						

							LED Cinema Display (27-inch) Troubleshooting — General Troubleshooting 15 2010-11-18
Block Diagram
Refer to this diagram to see how modules are interrelated:  
						

							LED Cinema Display (27-inch) Troubleshooting — General Troubleshooting 16 2010-11-18
Test Points Diagram
Test Points for DC Power Presence
Following  are  test  points  you  can 
use  to  verify  proper  power  flow   in 
the  LED  Cinema  Display.  All  voltages 
assume  that  the  display  is  only 
plugged   into  a  power  outlet,  and 
NOT into the host computer.
How to proceed: 
•Turn  the  dial  of  your   voltmeter/
multimeter  to  measure  DC  (direct 
current).  If  your  voltmeter  requires 
that  you  set  a  voltage  range, 
choose  a  DC  range  that  includes 
the voltage that you are measuring. 
• Connect the black  probe to  ground 
by  gently  inserting  into  any  of  the 
logic board corner screws posts. 
• To u c h  t h e  r e d   p r o b e  t o  t h e 
appropriate test point. 
• Verify voltage on multimeter.
• For the USB  power presence, plug  a 
known-good   iPod,  iPad  or  iPhone 
device  and  check  for   a  spark  icon 
visible on the device LCD display.DC In 24.5 V DC
 
12.0 V DC
*5.1 V DC
*even if USB is 
not plugged into  host computer
3.3 V DC
USB power and charge f iPod, 
iPad and iPhone
Warning ! HIGH VOLTAGE : 
Use extreme caution when working 
around the power supply.
• Never touch the leads on bottom and left  
side of the power supply around the 
warning sign.
• Do NOT lean over or accidentally touch 
power supply area during living testing.
• Keep your fingers behind the finger 
guards of the test probes when making 
measurements !    
						

							LED Cinema Display (27-inch) Symptom Charts — Startup and Power Issues 17 2010-11-18
Symptom Charts
Follow steps in the order indicated below. If an action resolves the issue, retest system to verify.
Startup and Power Issues
Dead Unit / No Power
Unlikely cause: fan, camera, speakers, subwoofer, microphone
Quick Check
SymptomsQuick Check
Dead Unit / No Power
•  No power
•  No image
•  No fan spin
•  No active MagSafe LED when 
MagSafe is connected to a 
MacBook /MacBook Pro
•  No iPod/iPhone/iPad is 
charged/powered when 
connected to USB ports on 
display  1.
  Verify power cord and AC wall outlet.
2.  Verify USB/Mini DisplayPort/MagSafe connectors 
are fully seated.
3.   Check brightness setting.
4.  Verify display is used with a supported system 
with up-to-date system software.
5.   Test display with a known-good system.  
If used as second display, open Display 
Preferences (or press Option-F2) and check for 
presence of the middle Arrangement tab to 
confirm that display is recognized.
Deep Dive
Check ResultAction Code
1.   Connect display to a known-
good supported computer and 
check in System Profiler’s USB 
device tree that display’s USB 
hub and built-in camera are 
listed. Yes
Power is present on the 
display logic board.  
Go to Blank / No Video, No 
Backlight.
No Go to step 2.
2.  Unplug and replug Mini 
DisplayPort connector into 
a known-good supported 
portable computer and 
monitor the portable’s display. 
Verify that portable’s display 
briefly turns off then back on. Yes
LCD panel is powered and 
video signal is asserted.  
Go to Blank / No Video, No 
Backlight.
No Go to step 3.  
						

							LED Cinema Display (27-inch) Symptom Charts — Startup and Power Issues 18 2010-11-18
3.  Remove glass and LCD panel, 
reconnect MagSafe, DisplayPort 
and USB cables to a powered 
on computer. Set digital 
multimeter to DC and correct 
range, and verify that:
- a 23.3–25.7 V DC voltage is 
present between logic board 
test point (24 V ) and chassis 
ground (GND); this circuit 
powers LCD backlight; and 
- an 11.4-12.6 V DC voltage is 
present between logic board 
test point (12 V ) and chassis 
ground (GND); this circuit 
powers everything else. Yes
24.5 V DC and 12.0 V DC 
from power supply are both 
present. Go to step 4.
No Either 24.5 V DC or 12.0 V 
DC or both have no power 
or incorrect power at logic 
board, indicating a power 
supply issue. Unplug AC 
power cord from display, wait 
a moment, then reconnect AC 
power cord and retest.  
 
If issue persists, go to step 6.
4.  Verify that a 3.1-3.5 V DC 
voltage is present between 
logic board test point (3.3 V DC) 
and chassis ground (GND). Yes
3.3 V DC present on logic 
board. Go to step 5.
No No 3.3 V DC power at logic 
board. Go to step 9.
5.   Verify that a 4.8-5.5 V DC 
voltage is present between 
logic board test point (5 V DC) 
and chassis ground (GND). Yes
All DC voltages present on 
logic board; power OK. Go 
to Blank / No Video, No 
Backlight, Step 3
No No 5.1 V DC present at logic 
board. Go to step 9.
6. Verify all connections between 
AC inlet, power supply, all-in-
one cable, and logic board 
are secure. See Functional 
Overview. Yes
If connections are secure and 
display still does not function 
correctly, go to step 7.
No Reseat connectors and retest. 
7.  Set digital multimeter to AC 
setting and range to 500 V 
AC, then locate the two AC 
pins on lower right of power 
supply, and v erify that a 100-
240 V AC voltage (depending 
on your local AC voltage) is 
present between the two pins. 
WARNING! Make sure that 
your fingers do not touch 
metal part of probes, any pins 
of power supply, or any other 
part of the live power supply 
with fingers! Yes
Go to step 8.
No No AC power available to 
power supply input.  
Replace AC inlet by replacing 
rear housing.  
 
X03  
						

							LED Cinema Display (27-inch) Symptom Charts — Startup and Power Issues 19 2010-11-18
8. Disconnect all connectors from 
the logic board EXCEPT the 
DC power cable. Set digital 
multimeter to DC and correct 
range, and verify that a 3.1-3.5 V 
DC voltage is present between 
logic board test point (3.3 V 
DC) and chassis ground (GND), 
then verify that a 4.8-5.5 V DC 
voltage is present between 
logic board test point (5 V DC) 
and chassis ground (GND). Yes
Power sources appear 
OK when all devices 
disconnected. Suspect 
possible damaged connector, 
short, faulty internal USB, 
audio or fan control device. 
Reconnect connectors one 
at a time and retest for 3.3 V 
DC and 5 V DC presence each 
time. When any of the 3.3 V 
DC or 5 V DC voltages cannot 
be read anymore, replace 
part that causes their power 
failure. Go to step 10.  
 
 
 
 
 
 
 
 
 
 
X03
No The master 12 V DC power 
presence needs to be 
checked. Go to step 9.
9.   Disconnect all connectors from 
the logic board EXCEPT the 
power supply to logic board 
cable. Set digital multimeter 
to DC and correct range, and 
verify that an 11.4-12.6 V DC 
voltage is present between 
logic board test point (12 V DC) 
and chassis ground (GND). Yes
12 V DC master power 
present, but 5 V DC and 3.3 V 
DC are missing:  replace logic 
board and retest the 12V DC 
presence. Go to step 10.  
 
M01
No Faulty 12 V DC source or logic 
board shorting it: replace 
logic board and retest 12V DC 
presence. If issue persists after 
logic board replaced, replace 
power supply and retest.  
Go to step 10.  
M01   
 
 
P01
10.  Before reinstalling LCD panel 
into rear housing,verify that 
LED backlight driver cable on 
LCD panel is not damaged 
(wires not pinched nor 
shorted).  Yes
Test reassembled display to 
make sure it is fully functional.
No LED backlight driver cable 
with pinched or shorted wires 
is likely the cause of board 
damage. Replace LCD Panel 
and take care not to pinch 
any cable during reassembly. 
Test reassembled display to 
make sure it is fully functional. L01  
						

							LED Cinema Display (27-inch) Symptom Charts — Startup and Power Issues 20 2010-11-18
MagSafe Adapter – No Power
Unlikely cause:  LCD panel, logic board, fan, camera, speakers, subwoofer, microphone
Quick Check
SymptomsQuick Check
MagSafe Adapter – No Power
•  No power available to MagSafe 
connector
•  MagSafe connector status LED 
does not illuminate 1.
  Verify power cord and AC wall outlet. 
1.   Verify USB/Mini DisplayPort/MagSafe connectors 
are fully seated.
2.  Verify display is operating.
3.   Ensure MagSafe connector and receptacle on 
MacBook or MacBook Pro are clean.
4.  Verify LED glowing green or orange/amber when 
MagSafe connector attached to a known-good  
MacBook or MacBook Pro.
Deep Dive
Check ResultAction Code
1.   Attach MagSafe cable to 
known-good supported 
portable computer. Verify 
connector status LED 
illuminates green or orange/
amber. Yes
MagSafe LED illuminates 
green or orange/amber 
depending on charging state. 
Go to step 4.
No Go to step 2.
2.  Visually inspect MagSafe cable 
and user’s portable MagSafe 
receptacle for physical damage, 
stuck pins, debris, or metal 
fragments.  Yes
See kBase #TS1713: Apple 
Portables: Troubleshooting 
MagSafe adapters. 
Go to step 4.
No Go to step 3.
3.   Unplug and replug the display’s 
AC power cord, and verify that 
MagSafe connector LED color 
illuminates green or orange/
amber depending on charging 
state. Yes
Go to step 4.
No Replace all-in-one cable. P15
4.  Verify a known-good 
supported portable computer 
simultaneously operates and 
charges a discharged battery 
to 100% from the display’s 
MagSafe cable. Yes
Repair complete.
No
Replace power supply.   
If needed afterwards, refer to 
Dead Unit/No Power. P01