Apple imac 17 inch flat panel User Manual

							 iMac (17-inch Flat Panel)  Take Apart - 99
 Neck Assembly• Remove the fan bracket.
• Remove the neck spoke retainer cap.
• Remove the blind mate connector screws.
• Remove the Faraday cage.
• Remove the outer plastic housing.
• Remove the flat panel display.
• Remove the back cover 
Procedure
The neck assembly is attached to the computer base at one end and to the flat panel 
display at the other end. To remove the neck assembly from the computer, follow all the 
take-apart procedures. When you are finished, you will be left with the neck assembly 
shown below. 
						

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 Service Source
Troubleshooting
iMac (17-inch Flat Panel) 
						

							iMac (17-inch Flat Panel) Troubleshooting - 1
 General Information
General Information
What’s New and Different:
1.Important: If you are replacing the display, be sure to install the new display shield and EMI gaskets that 
come with the new LCD panel. Installation instructions are included with the new display panel. 
Additional display shields/gasket kits are also available separately as a kit, part #076-0958.
2. The LED and microphone are part of the display bezel (922-5297); they cannot be ordered separately.
3. The LED functions differently on the iMac (17-inch Flat Panel). The LED does not light up when the 
power is on; however, the LED should pulse when the computer is in Sleep mode.
4. Diagnostic test points have been added to the logic board. They are accessed through the user access 
door. Use the test points to check the following:
• Battery
•5V
• Main 
• 12V
For more information, refer to the “Logic Board Battery” and “No Power” topics later in this 
chapter.
5.Important: The CPU uses a thermal pipe to transfer heat away. This pipe makes a thermal connection to 
the top metal chassis (Faraday cage) at two locations. These connecting points must be cleaned and 
have new thermal paste applied each time the bottom housing is removed. If the mating surfaces are not 
cleaned and thermal paste is not used, the CPU may overheat and become damaged. There is no 
exception to this. Note:  Most service procedures require that the bottom housing is removed. 
Refer to “Thermal Paste Application” mentioned later in this chapter or in the Take Apart 
chapter.
6. The procedures for removing and replacing the display panel and the inverter board are new and 
different. Refer to the Take Apart chapter for additional information. Important: Whenever the LCD 
display (661-2715) is replaced, a display shield/gasket kit (076-0958) must be installed on the new panel. 
Instructions for installing the shield/gasket kit are included with the new LCD panel.
7. The AirPort antenna cable is no longer bundled in the neck assembly. The antenna is now clipped to the 
outside of the Faraday cage. Refer to the Take Apart chapter for additional information.
Important Things to Remember:
Service items that still apply to all flat-panel iMac computers:
1.Important:  Whenever the logic board is separated from the bottom housing, you must install new 
thermal pads to three surfaces on the bottom housing. The thermal pads help cool components on the 
logic board. Failure to apply these pads whenever the logic board is separated from the bottom housing  
						

							2 - iMac (17-inch Flat Panel) Troubleshooting
 General Information could cause these parts to overheat. Short term separation, where the thermal pads are not handled 
excessively 
(an exception would be if you are simply testing the logic board and only detach it for a few 
minutes), does not require replacement. Refer to “Thermal Pad Installation” in this chapter for detailed 
information.
Refer to the Take Apart chapter, “Thermal Pad Installation.”
2.  Whenever the bottom housing is opened for service, you must do two things:
1.You must clean the original thermal film from the surfaces joining the thermal interface layer and 
reapply thermal paste to the thermal pipe.
2. You must tighten the four torx screws on the bottom housing to a minimum of 17 in.-lbs. If you do 
not have a torque driver, you will have to make sure these screws are tightened by hand FIRMLY, 
BUT NOT FORCIBLY. Or, purchase the service tool (076-0899) in order to ensure the thermal pipe is 
firmly mated with the top base. If the bottom housing is not securely attached to the base in this 
fashion, the CPU may overheat and become damaged. Failure to follow either of these steps could 
cause the computer to overheat and damage internal components. 
Refer to the topic, “Thermal Paste Application” for detailed information.
3. Special service tools are required to perform some procedures. A service stand, 076-0898, to hold the 
unit during take apart, and service cables, 076-0897, that allow the unit to be powered on while the 
bottom housing is open. Important: The unit should not be powered on for more than five minutes with 
the bottom housing open. If it is open longer, the CPU may overheat and become damaged. 
						

							iMac (17-inch Flat Panel) Troubleshooting - 3
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Logic Board, Top
Note: Enlarge the page to view the graphic at a larger size. 
						

							4 - iMac (17-inch Flat Panel) Troubleshooting
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Logic Board, Bottom
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							iMac (17-inch Flat Panel) Troubleshooting - 5
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I/O Ports
Service Cables
Three extension cables (076-0897) are required when troubleshooting the iMac with the bottom 
housing open, as shown below. 
Important:  Diagnostic service cables allow the unit to run while the 
bottom housing is open; however, the computer cannot run for more than five minutes with the bottom 
housing open. If it is open longer, the CPU may overheat and become damaged.
Connect the cables as shown below. 
A= power cable
B= drive data cable
C= blind mate connector
Note: Enlarge the page to view the graphic at a larger size. 
						

							6 - iMac (17-inch Flat Panel) Troubleshooting
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The PMU Chip
The PMU (Power Management Unit) is a microcontroller chip that controls all power functions 
for the computer. The PMU (location shown below) is a computer within a computer. It has 
memory, software, firmware, I/O, two crystals, and a CPU. Its function is to: 
• Tell the computer to turn on, turn off, sleep, wake, idle, etc.
• Manage system resets from various commands.
• Maintain parameter RAM (PRAM).
• Manage the real-time clock.
Important: The PMU is very sensitive and touching the circuitry on the logic board can cause the 
PMU to crash. If the PMU crashes, the battery life goes from about five years to about two days if 
the PMU is not reset. Refer to the next topic, “Resetting the PMU on the Logic Board” for the 
procedure. 
Many system problems can be resolved by resetting the PMU chip. The PMU reset button is 
located on the right side of the board, refer to the picture below. 
                                   Location of the PMU Button  
						

							iMac (17-inch Flat Panel) Troubleshooting - 7
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Resetting the PMU on the Logic Board
Resetting the PMU (Power Management Unit) on the logic board can resolve many system 
problems. Whenever you have a unit that fails to power up, you should follow this procedure 
before replacing any modules.
1. Disconnect the power cord.
2. Remove the user access panel from the bottom of the computer.
3. Press the PMU reset switch (shown below) once on the bottom side of the logic board and then proceed 
to step 3. Do NOT press the PMU reset switch a second time because it could crash the PMU chip.
4 WAIT ten seconds before connecting the power cord and powering the computer on. If the 
computer powers on, go to the next step. If the computer does not power on, there is something 
else wrong with the computer, refer to the symptom/cure, “No Power” in this chapter.
5. Run MacTest Pro and return the computer to the customer.
Note: This entire procedure resets the computer’s PRAM. Be sure to reset the computer’s time, 
date and other system parameter settings before returning the computer to the customer. 
						

							8 - iMac (17-inch Flat Panel) Troubleshooting
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Diagnostic Test Points
The iMac (17-inch Flat Panel) has four test points and one ground pad on the bottom of the logic board. 
These test points are accessible under the customer access panel via two small cutouts in the plastic 
shielding (see below).
These test points provide an easy troubleshooting tool for common problems. To use each test point, put 
the positive probe of your voltmeter on the test point, and the negative probe on the ground pad.