Apple imac 20 inch early 2008 User Manual

iMac (20-inch Early 2008)  Take Apart — Optical Sensor Cable 141
Optical Sensor Cable
Tools
Torx T6 screwdriver• 
Torx T6 screwdriver• 
Preliminary Steps
Before you begin, remove the following:
A
• ccess door
Glass Pane
• l
F
• ront bezel
LCD display pane
• l
Optical driv
• e
Part Location 

iMac (20-inch Early 2008)  Take Apart — Optical Sensor Cable 142
Removing the Optical Sensor Cable 
Disconnect the temperature sensor cable from the connector on the logic board. 1. 
On the bottom of the optical drive, peel back the foam gasket (not shown) covering the 2.  
sensor clip and disconnect the sensor from the sensor clip. This photo shows the location on 
the iMac (24-inch Mid 2007). The location is the same on the iMac (20-inch Mid 2007). 

iMac (20-inch Early 2008)  Take Apart — Optical Sensor Cable 143
Replacing the Optical Sensor Cable
Caution: Never press down on or grasp the body of the optical drive when installing it. Pressing 
or squeezing the body of the optical drive could damage the drive mechanism. 
Connect the optical sensor cable to the sensor clip on the underside of the drive. Place the 
1. 
foam gasket on top of the sensor clip.
2.  Replace the optical drive .
Connect the other end of the sensor cable to the connector on...

iMac (20-inch Early 2008)  Take Apart — Logic Board 14 4
Logic Board
Tools
Torx T8 screwdriver• 
Torx T10 screwdriver• 
Preliminary Steps
Before you begin, remove the following:
A
• ccess door
Glass pane
• l
F
• ront bezel
LCD display pane
• l
Speaker, right
• 
Part Location 

iMac (20-inch Early 2008)  Take Apart — Logic Board 145
Removing the Logic Board 
Disconnect the highlighted connectors from the logic board. 1. Note: The IR and Bluetooth 
cables do not have to be disconnected to remove the logic board.
s
2.  Remove the tenT10 screws and the two T8 screws from the logic board. Note that the 
machine screw locations have an arrow designation stamped onto the metal backer plate .
922-8173
922-6800
922-6842
922-8175 

iMac (20-inch Early 2008)  Take Apart — Logic Board 146
Lift the logic board up and out of the rear housing. 
3. 
Important4.
 :  When handling the logic board, never handle the board by the heatsink or metal 
frame.
Transfer the following items from the logic board to the replacement logic board:5. 
Video card
•	
Audio board
•	
AirPort card
•	
IR board and cable
•	
Bluetooth board and cable
•	
Memory DIMMs
•	
Black plastic cable holder (located below the IR board and heatsink)
•	 

iMac (20-inch Early 2008)  Take Apart — Logic Board 14 7
Important
6.
 : Verify that the tamper indicator labels on the front and back side of the CPU heat 
sink assembly are intact. If the tamper labels have been removed or tampered with, the logic 
board is not eligible for exchange.
This shows the tamper-proof label on the top side of the logic board.7.   

iMac (20-inch Early 2008)  Take Apart — Logic Board 14 8
Replacing the Logic Board
If you removed the logic board to access another module, reinstall the board as is. However, 1. 
if you are replacing the logic board with a new one, make sure the following parts are 
transferred to the new logic board:
Video card
•	
Audio board
•	
AirPort card
•	
IR board and cable
•	
Bluetooth board and cable
•	
Memory DIMMs
•	
Black plastic cable holder (located below the IR board and heatsink) 
•	
Note
2.  : A piece...

iMac (20-inch Early 2008)  Take Apart — Logic Board 149
As you lower the board into the rear housing, line up the two T8 screw holes on the right 
4.
 
and left side of the memory slots.  Continue lowering the board into place lining up the 
other screw holes.  
5. Replace the machine screws first; then replace the self-tapping screws.
Replace the right speaker and connect the cable to the audio board.6. 
922-6842
922-8173
922-6800
922-8175 

iMac (20-inch Early 2008)  Take Apart — Logic Board 150
Connect the following cables on the right side of the board. Note their cable routing.
7.
 
AirPort antennas
•	
Bluetooth antenna
•	
Bluetooth cable (to the logic board)
•	
Optical fan cable (to the right of the optical cable clip)
•	
Microphone cable (to the audio board)
•	
Left speaker cable (to the audio board)
•	
Hard drive SATA cable
•	
Camera cable
•	
IR cable (if it was removed)
•	
8.  At the top of the board, connect the hard drive sensor...