Apple imac 17 inch flat panel User Manual

							iMac (17-inch Flat Panel) Troubleshooting - 9
 General Information
Logic Board Battery
Important: Apple highly recommends removing the battery when handling the logic board. Make 
sure to use proper ESD protection when handling modules.
The battery on the logic board controls the stored system settings, such as date and time. It is only 
necessary to test the battery when you can’t power on the computer, or the date and time are reset 
every time the AC power is removed. 
The battery is also used to power the PMU chip (because the PMU chip keeps time and must always 
be running) when the computer is unplugged from the wall (AC power). The PMU is 
very sensitive 
and touching any circuitry that is connected to the PMU can cause it to crash. If the PMU crashes, 
the battery life goes from about five years to about two days if the PMU is not reset. Once the 
battery goes dead, the PMU will reset the time and date every time the AC power is removed. To fix 
this situation, replace the battery and reset the PMU (refer to “Resetting the PMU on the Logic 
Board” mentioned earlier in this chapter).
If the computer has a “No Power” situation, check the battery before replacing modules. 
Testing the Battery
1. Remove the user access door on the bottom of the computer.
2. Locate the battery test point.
3. With the computer powered off, measure the battery voltage. Does the battery measure at least +3.5v? If 
no, replace the battery and reset the PMU. If the battery measures +3.5v or higher, reinstall the battery 
and reset the PMU as above.  
						

							10 - iMac (17-inch Flat Panel) Troubleshooting
 General Information 4. Connect the power cord and power up the system again. 
Warning:
 Whenever the bottom housing is opened for service, you must do two things:
1. You must clean and reapply thermal paste to the thermal pipe surface.
2. You must tighten the four torx bolts on the base unit to a minimum of 17 in.– lbs. Failure to follow 
either of these steps could cause the computer to overheat nd damage internal components. 
Refer to the next topic, “Thermal Paste Application” for detailed information. 
						

							iMac (17-inch Flat Panel) Troubleshooting - 11
 General Information
Thermal Paste Application
The following instructions explain how to apply thermal paste to the thermal pipe in the iMac (17-inch Flat 
Panel) computer. Failure to follow these instructions could cause the computer to overheat and damage 
internal components.
Tools
This procedure requires the following tools:
• Plastic stylus or plastic spatula to remove the old thermal paste
• Plastic stylus or plastic spatula to spread the thermal paste
• Thermal paste (922-4757)
Paste Location 
						

							12 - iMac (17-inch Flat Panel) Troubleshooting
 General Information
Procedure
1. Thoroughly clean the original thermal film from the four mating surfaces circled below. Use a plastic 
stylus to scrape the surfaces clean. Note:  Do not use an abrasive material or liquid cleaner.
2. Squeeze a drop of thermal paste onto the thermal pipe locations circled below. 
3. Close the bottom housing.
 Warning: The bottom housing has four torx screws that must be tightened to at least 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. 
						

							iMac (17-inch Flat Panel) Troubleshooting - 13
 General Information
Thermal Pad Replacement Instructions
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 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.
Procedure
1. Remove the old thermal pads (circled below) from the bottom housing. Thoroughly clean the bottom 
housing surfaces after removing the pads. Note: If you don’t see all three thermal pads on the bottom 
housing, check the bottom side of the logic board. 
2. Using the thermal pad kit, remove the clear protective backing from the new thermal pads. 
3. Place the new thermal pads in the bottom housing. Note: Avoid unnecessary contact with either side of 
the thermal pad as dirt and body oils reduce the thermal pads conductivity.
4. Press down on the blue protective backing to make sure each thermal pad has even contact with the 
bottom housing. There should be no air pockets.
5. Remove the blue protective backing from the new thermal pads. 
6. Replace the logic board. Holding the logic board by the battery retainer and the internal drive cable 
connector, slide the logic board back into the bottom housing (make sure the I/O port covers are on the 
logic board).  
						

							14 - iMac (17-inch Flat Panel) Troubleshooting
 Symptom Charts
Symptom Charts
How to Use the Symptom Charts
The Symptom Charts included in this chapter will help you diagnose specific symptoms related to the 
product. Because cures are listed on the charts in the order of most likely solution, try the cures in the 
order presented. Verify whether or not the product continues to exhibit the symptom. If the symptom 
persists, try the next cure. 
Note:  If you have replaced a module, reinstall the original module before you proceed to the next cure.
Apple Hardware Test
Apple Hardware Test is a diagnostic tool for detecting problems with Apple internal hardware components 
such as logic board, memory, modem, video RAM, and Apple AirPort Card. The test does not check 
externally connected hardware components such as USB or FireWire devices; it also does not check non-
Apple devices such as third-party PCI cards. 
Note:  The most recent Apple Hardware Test software can be downloaded from the CD Images page on 
AppleCare Service Source; go to the Service Source home page and select ‘Disc Images’ from the quick-
click table.
Error Codes
If Apple Hardware Test detects a problem with a computer, it displays an error code, which is defined in the 
products Error Code List. Consult the list for appropriate repair procedures associated with the code.
All Error Code Lists are included in the Service Diagnostics Matrix, Knowledge Base article 112125. You 
can also access this matrix by clicking the Service Diagnostics rollover link under any of the product areas 
on the Service Source home page. 
						

							iMac (17-inch Flat Panel) Troubleshooting - 15
No Power Symptom Charts
No Power 
No fan, no hard drive noise, and the screen is black.
1. Verify the power outlet is good. Plug a different device into the socket to ensure there is power, or plug 
computer into another outlet.
2. Check the power cord. Use a known good power cord.
3. Check connection of the power cord on both ends. Verify that the plug is securely plugged into both the 
A/C outlet and back of the computer.
4. Remove keyboard, mouse, and other peripherals such as speakers.
5. Disconnect the power cord, place the computer in the service stand, and remove the user access plate.
6. Reset PMU. Refer to “Resetting the PMU on the Logic Board” mentioned earlier in this chapter.
7. Using a voltmeter, check the voltage on the battery test point (see graphic below). If the reading is over 
3.5 volts, go to the next step. If the reading is under 3.5 volts, replace the battery and test again. 
8. Plug the unit in, but do NOT press the power button. Using a voltmeter, check the voltage from the test 
point marked “Main” (see graphic above). You should get a reading of approximately 12 volts. If the 
reading is 12 volts, go to the next step. If you don’t get a 12 volt reading, verify that all the cables are 
securely connected and test the unit again. Pay special attention to the video cable.
9. Press the power switch on the computer. Using a voltmeter, check the voltage on the test point marked 
“12v” (see graphic above). You should get a reading of approximately 12 volts. If the reading is 12 volts, 
go to the next step. If you do not get a 12 volt reading, replace the main logic board.
10. Using a voltmeter, check the voltage on the test point marked “5v” (see graphic above). You should get a 
reading of approximately 5 volts. If the reading is 5 volts, go to the next step. If you do not get a 5 volt 
reading, replace the main logic board. 
						

							16 - iMac (17-inch Flat Panel) Troubleshooting
No Power Symptom Charts 11. Remove the bottom housing. Warning:  Whenever the bottom housing is opened for service, you must 
do two things:
• You must clean the original thermal film from the surfaces joining the thermal interface layer and 
reapply thermal paste to the thermal pipe.
• The bottom housing has four torx screws that must be tightened to at least 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.
12. Check the AC line filter. To measure power at the AC line filter cable, disconnect the AC line filter cable 
from the power supply cable. Switch your multimeter to read AC voltage. Touch the black probe to the 
pin of the brown wire, and touch the red probe to the pin of the blue wire (see graphic below). Do you 
measure 120v (line voltage)? If yes, reconnect the AC line filter and go on to the next step. If no, 
replace the AC Line Filter.
13. Connect the diagnostic cables (part 076-0897) between the upper housing components and the logic 
board. Refer to “Service Cables” mentioned earlier in this chapter. 
14. Check the connection of the video cable on the LCD flat panel, and try to power on the unit again. If 
you still have no power, go on to the next step. 
						

							iMac (17-inch Flat Panel) Troubleshooting - 17
No Power Symptom Charts 15. Check power supply output. Disconnect the diagnostic power cable from the power supply connector, 
and measure power at the power supply connector by touching the black probe to the ground pin, and 
using the red probe to measure power at the pins indicated in the graphic below. Did you measure +12v 
at each point? If yes, replace the logic board. If no, replace the power supply.
16. Replace the inverter board.
17. Replace the neck assembly. 
						

							18 - iMac (17-inch Flat Panel) Troubleshooting
No Video Symptom Charts
No Video 
Screen is dark, fan is running and the hard drive is spinning. You may hear the startup 
chime as well.
1. Reset parameter RAM. Press Command-Option-P-R during startup before “Welcome to Macintosh” 
appears.
2. The system software could be damaged. Start up from the system CD that came with the computer.
3. Remove the user access panel. With the unit powered on, check if a red LED (shown below) is visible 
in the access door. If the red LED is on, power is on. If you don’t see the LED glowing red, follow the 
steps under the symptom “No Power”. 
4. Disconnect the A/C power cord. Place the unit in the service stand and remove the user access plate. 
Press the PMU reset button on the logic board. Refer to “Resetting the PMU on the Logic Board” 
mentioned earlier in this chapter.
5. Check for external video. Connect an external monitor to the mini-VGA port. If you don’t have external 
video, replace the main logic board. If you do have external video, go on to the next step.
6. Open the bottom housing and verify that all the cables are securely attached. Pay special attention to 
the video cable (located near the modem). If the cables are securely attached, go on to the next step. 
Warning:  Whenever the bottom housing is opened for service, you must do two things:
• You must clean the original thermal film from the surfaces joining the thermal interface layer and 
reapply thermal paste to the thermal pipe.
• The bottom housing has four torx screws that must be tightened to at least 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.
7. Check the connection of the video cable to the LCD flat panel display (under black tape).