Apple led cinema display 24inch User Manual

							LED Cinema Display (24-inch) Basics — Serial Number Location 11 2010-11-25
Serial Number Location
Serial Number on Stand
The LED Cinema Display (24-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 (24-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.  
						

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 Apple Technician Guide 
Troubleshooting
LED Cinema Display (24-inch)   
						

							LED Cinema Display (24-inch) Troubleshooting — General Troubleshooting 13 2010-11-25
General Troubleshooting
Troubleshooting Theory
For general information on troubleshooting theory, go to GSX and find the Service Training 
c ourse 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   
						

							LED Cinema Display (24-inch) Troubleshooting — General Troubleshooting 14 2010-11-25
Functional Overview
A guide to possible symptoms as they relate to ports on the main logic board:
LCD Function Interface• No power to LCD
• No LED backlightDC In• No power
Camera• Not detected in USB Device Tree
• No green camera LED
• No camera video
Fan (1) & LCD (2) Temp Sensors• Fan runs fast if sensor is:     ° disconnected     ° connected to wrong location on MLB     ° not properly mounted or located     ° faulty
Microphone• Not detected in Sound Pref pane
• No, low, distorted audio input 
Subwoofer• No, low, distorted bass 
Right & Left Speakers• Not detected in Sound Pref pane
• No, low, distorted channel(s) 
Blower (Fan)• No rotation leading to overtemp condition
• Excessive noise/vibration due to faulty fan
* Also see Fan (1) & LCD (2) Temp Sensors 
symptoms below. 
LED Driver (Backlight)• No LED backlight
• Dim or low brightness
Upstream USB• Not detected in USB Device Tree or 
System Preference panes
     ° iSight camera     ° Sound output      ° Microphone input      ° LED calibration &  
        brightness control
     ° 3 x USB ports    
						

							LED Cinema Display (24-inch) Troubleshooting — General Troubleshooting 15 2010-11-25
Block Diagram
Refer to this diagram to see how modules are interrelated:  
						

							LED Cinema Display (24-inch) Troubleshooting — General Troubleshooting 16 2010-11-25
Cable Routing Diagram  
						

							LED Cinema Display (24-inch) Troubleshooting — General Troubleshooting 17 2010-11-25
Test Points Diagram
Refer to this diagram to see the location of test points and instructions for their use:
Below are main logic board test points that you can use 
to verify proper power flow in LED Cinema Display (24-inch). 
All voltages assume that the display is plugged into 
a power outlet, and NOT into the host computer (unless 
otherwise noted). 
• 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 LCD screw posts closest to the logic board. 
Keep in mind that the threading in the screw posts is fragile 
and can be easily destroyed.
• Touch the red probe to appropriate test point. 
• Verify voltage.
DC In
TP 11:    24.5 VDC
TP 12:    24.5 VDC
TP 13:    12.0 VDC
*TP 14:    5.0 VDC 
*only if USB plugged into host
USB Hub 1 for 3 ports
*TP 21:    3.3 VDC
*TP 22:    5.2 VDC
*TP 23:    5.2 VDC
*TP 24:    5.2 VDC 
*only if USB plugged into host
USB Hub 2 for camera & audio
*TP 31:    3.3 VDC*only if USB plugged into host
LED Backlight Driver
TP 81:    24.5 VDC
TP 82:      1.0 VDC
TP 61:  3.3 VDC
Warning:
HIGH VOLTAGE: Use extreme caution 
when live testing. 
• Never touch the power supply. 
• Do NOT lean over or accidentally touch 
power supply area during live testing. 
• Keep your fingers behind the finger 
guards on the test probes when making 
measurements on main logic board!  
						

							LED Cinema Display (24-inch) Symptom Charts — Startup and Power Issues 18 2010-11-25
Symptom Charts
Follow steps in the order indicated below. If an action resolves the issue, retest system to verify.
Note: A compilation of Quick Check tables is available at:
http://service.info.apple.com/QRS/en/quickreference.pdf
Startup and Power Issues
Dead Unit / No Power
Unlikely cause:  LCD panel, fan, subwoofer, speakers, camera, microphone
Quick Check
SymptomsQuick Check
Dead Unit / No Power
•
 
N
 o power
•
 
N
 o image
•
 
N
 o fan spin
•
 
N
 on-operational 1.
 V

erify power source.
2.
 V

erify USB/display/power connectors are fully 
seated.
3.
 V

erify display is used with supported system.
4.
 U

se with known-good system. 
If used as second display, check display 
preferences to see if display is recognized.
5.
 C

heck brightness setting.
Deep Dive
CheckResult Action Code
1.
 V
 erify display’s USB hub and 
built-in camera are listed in the 
System Profiler’s USB device 
tree. Yes
Power supply OK. Go to 
Blank/No Video.
No Go to step 2.
2.
 U

nplug and replug the Mini 
DisplayPort connector into a 
supported system and monitor 
the portable’s display. Verify 
that the portable’s display 
briefly turns off then back on. Yes
Logic board OK.  
Go to Blank/No Video.
No Go to step 3.  
						

							LED Cinema Display (24-inch) Symptom Charts — Startup and Power Issues 19 2010-11-25
3. Remove LCD panel and disconnect LCD function 
interface cable. Verify voltage 
on logic board between test 
point TP11 (24.5VDC) and 
chassis ground (GND) is  
23.3–25.7 VDC. Yes 24.5VDC from power supply 
OK. Go to step 4.
No No power or incorrect power  at logic board. 
Go to step 6.
4. Verify voltage on logic board between test point TP61 
(3.3VDC) and chassis ground 
(GND) is 3.1–3.5 VDC. Yes 3.3VDC power on logic board 
OK. Go to step 5.
No No power at logic board.      Go to step 9.
5. Verify voltage on logic board between test point TP13 
(12VDC) and chassis ground 
(GND) is 11.4–12.6 VDC. YesAll DC voltages present on 
logic board; power OK. Go to 
Blank/No Video, Step 3.
No No power at logic board.      Go to step 9.
6. Verify all connections between 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 8.
No Reseat connectors and retest. 
7. Disconnect power supply cable  from logic board. Verify cable 
voltage at connector between 
Pin 1 and chassis ground 
(GND) is 14.3–15.8 VDC.  Yes Go to step 8.
No
No power or incorrect power 
to logic board. 
Replace power supply. P01
8. Disconnect all connectors from 
the logic board EXCEPT the 
power supply cable.  
Verify voltage on logic board 
between test point TP11 
(24.5VDC) and chassis ground 
(GND) is 23.3-25.7 VDC.  Yes Power supply OK. Suspect 
possible short, damaged 
connector, or faulty sensor/
fan/speaker. Reconnect 
connectors one at a time and 
retest for 24.5VDC at TP11. 
Replace affected part that 
causes the 24.5VDC voltage to 
disappear.  L14
No
Replace power supply. P01  
						

							LED Cinema Display (24-inch) Symptom Charts — Startup and Power Issues 20 2010-11-25
9. Disconnect all connectors from the logic board EXCEPT the 
power supply cable.  
Verify voltages on logic 
board between test points 
TP61 (3.3VDC) and chassis 
ground (GND) is 3.1–3.5 VDC, 
and between TP13 (12VDC) 
and chassis ground (GND) is 
11.4–12.6 VDC. Yes Power supply OK. Suspect 
possible short, damaged 
connector, or faulty sensor/
fan/speaker. Reconnect 
connectors one at a time 
and retest for 3.3VDC at TP61 
and 12VDC a t TP13. Replace 
affected part that causes the 
3.3VDC or 12VDC voltages to 
disappear.  L14
No
Replace logic board. L01
Burnt Smell/Odor
Unlikely cause:  LCD panel, fan, subwoofer, speakers, camera, microphone
Quick Check
Symptoms Quick Check
Burnt Smell/Odor
•
 
N
 o power
•
 
N
 o image
•
 
N
 o fan spin
•
 
N
 on-operational 1.
 V

erify source of smell/odor is emanating from the 
display. 
2.
 V

erify display is functional.
3.
 R

emove air vent obstructions.
Deep Dive
CheckResult Action Code
1.
 V
 erify by visual inspection of 
each module the location the 
source of burnt smell/odor Yes Located affected module.     
Go to step 2.
No
Not able to locate affected 
module.  Go to  
Dead Unit / No Power.
2.
 V

erify no other modules or 
internal cables are affected or 
the root cause. Yes Replace all affected module(s) 
and/or cable(s). P08
No Return unit to user.