Apple imac 20 inch late 2006 User Manual

							iMac (20-inch Late 2006) Troubleshooting — General Info 151
General Information
Serial Number Location
iMac (20-inch Late 2006) serial numbers are located on the bottom of the computer stand.
Block Diagram 
.
.
CPU
Merom
2.0/2.16 GHz
Northbridge Calistoga945GM
FSB 667 MHz
Southbridge ICH7M
DMI
GPU
A TI M56
Frame
Buf fer
Voltage
Regulator IMVP
SODIMM 0
SODIMM 1
SA TA
Parallel
ATA
Azalia Audio
Realtek
ALC885Line-In &  S/PDIF
Headphone & S/PDIF
USB
USB
USB
Ethernet
10/100/1G
Marvell YukonPCIE x1
FireW ire
400 Mb
Agere FW323PCI 33 MHz6 pin6 pin
RJ45Speaker amp
SMC
Renesas
H8S/21 16
Boot
ROM
Linda card 
Override ROM,  Port 80, 
serial port accessLPCCamera
AirPortM35a/bUSB2.0
HD Audio
mini-DVI
TMDS &  VGA
Internal
Display L VDS
(dual channel) 
Internal
mic
PCIE x16 / SDVO
            SMC functions:
• LED control
•ALS (Ambient Light Sensor)
• V oltage & Current Sensors
• Power Switch Intercept
• Fan Control
• Flash ROM Self-Update
• Power management
PCIE x 1
SPI
Bluetooth M13d
DDR2667 MHz
TPM 1.2 
						

							iMac (20-inch Late 2006) Troubleshooting — General Info 15 2
Power On Self Test (POST)
Intel-based Macintosh computers such as the iMac (20-inch Late 2006) rely on a combination of 
tones and blinking LEDs to display Power On Self Test (POST ) error codes.
If the computer detects out-of-specification memory or no RAM installed, the screen will be black 
and the power LED on the front of the computer will blink once a second to indicate bad or no 
RAM. Bad RAM can include physically damaged, the incorrect type, or not present.
If the RAM is good enough to pass the POST test but it is marginal and cannot be used by the 
operating system, the computer will show a gray screen, three tones will sound and the power 
LED on the front of the computer will blink three times, pause, and repeat until the computer is 
turned off.
The solution to both these situations is to install known good memory.
DDR Memory
The iMac (20-inch Late 2006) computer has two SDRAM slots in the bottom of the computer. The 
iMac ships from the factory with at least 512 MB of DDR2 SDRAM, installed as a 256 MB DIMM in 
the top slot and a 256 MB DIMM in the bottom slot. ( The computer may come with more RAM, 
depending on how the computer was ordered from Apple.)
Although you can install a single SO-DIMM, it is recommended that memory be installed in 
matched pairs for improved graphics performance.
The maximum amount of RAM you can install in the iMac is 4 GB total (a 2 GB SO-DIMM in each 
of the two slots) but the computer will only use a maximum of 3 GB of RAM. You can use small-
outline dual inline memory modules (SO-DIMMS) that meet all of these criteria:PC2-5300
• 
unbuffered
• 
nonparity
• 
200-pin
• 
667 MHz DDR2 SDRAM
• 
Note:  DIMMs with any of the following features are NOT supported in this iMac:
registers or buffers
• 
PLLs
• 
ECC
• 
parity
• 
EDO RAM
•  
						

							iMac (20-inch Late 2006) Troubleshooting — General Info 15 3
How to Reset the System Management Controller (SMC)
The System Management Controller (SMC) is a chip on the logic board that controls all power 
functions for your computer. If your computer is experiencing any power issue, resetting the SMC 
may resolve it. The SMC controls several functions, including:Telling the computer when to turn on, turn off, sleep, wake, idle, and so forth.
• 
Handling system resets from various commands.
• 
Controlling the fans.
• 
Note that resetting the SMC does not reset the PRAM. Resetting the SMC will not resolve issues 
in which your computer is unresponsive—in these situations, restarting your computer will 
generally suffice. If your computer isn’t responding, perform these steps one at a time, in this 
order, until the issue has been resolved:
Force Quit (Option-Command-Escape).
1.  
Restart (Control-Command-Power).
2.  
Force Shut Down (press the power button for 10 seconds).
3. 
Resetting the SMC can resolve some computer issues such as not starting up, not displaying 
video, sleep issues, fan noise issues, and so forth. If your computer still exhibits these types of 
issues after you’ve restarted the computer, try resetting the SMC.
To reset the SMC
From the Apple menu, choose Shut Down (or if the computer is not responding, hold the 
1.  
power button until it turns off ).
Unplug all cables from the computer, including the power cord.
2.  
Wait at least 15 seconds.
3. 
Plug the power cord back in, making sure the power button is not being pressed at the time. 
4.  
Reconnect your keyboard and mouse to the computer.
5. 
Press the power button on the back to start up your computer.
6.   
						

							iMac (20-inch Late 2006) Troubleshooting — General Info 154
Diagnostic LEDs
The iMac (20-inch Late 2006) has three built-in diagnostic LEDs and a front power-on/sleep LED 
on the main logic board that can help you to troubleshoot the computer.
To Access the Diagnostic LEDs:
Follow the take apart instructions to remove the RAM 
1.   access door, front bezel,  and lower EMI 
shield .
Locate the SO-DIMM slot and LVDS video connector. The three diagnostic LEDs 1, 2, and 3 are 
2.  
located below the battery and to the right of the memory slot. Note that the LEDs are 
marked 1, 2, 3 as show below. An additional front bezel LED is located in an opening at the 
center of the right speaker, (see photo on the next page).   
v
 LED #1  Indicates that the trickle voltage from the power supply has been detected by the main 
• 
logic board. This LED will remain ON whenever the iMac is connected to a working AC power 
source. The LED will remain on even when the computer has been shut down or put to sleep. 
The LED will turn off only if the AC power source is disconnected or the power supply is 
faulty.
LED #2 Indicates that the main logic board has detected proper power from the power supply when 
• 
the computer is turned on. This LED will be ON when the computer is turned on and the 
power supply is working correctly. 
						

							iMac (20-inch Late 2006) Troubleshooting — General Info 15 5
LED #3
Indicates that the computer and the LCD display are communicating. This LED will be ON 
• 
when the computer is turned on and video signal is being generated.
Front LED Indicates that the computer has power but no video signal (e.g., the computer is starting up 
• 
or the display has entered Sleep mode, turning off the video signal). This LED will pulse when 
the entire system has entered Energy Saver mode.   
						

							iMac (20-inch Late 2006) Troubleshooting — Symptom Charts 156
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 a cure instructs you to replace a module, reinstall the original module before you 
proceed to the next cure. 
						

							iMac (20-inch Late 2006) Troubleshooting — Symptom Charts 15 7
Power Issues
No Power. 
The iMac will not turn on. The display remains black and there are no sounds from the fans or 
drives.
1. Verify the power outlet is good. Plug a different device into the socket to ensure there is power, 
or plug the iMac into another outlet. Does the iMac power on now?Yes. Resolved. Bad outlet.
No: Go on to the next step.
2. Check the power cord. Use a known good power cord. Does the iMac power on  now? Yes: Your power cord has failed. Replace the AC power cord.
No: Go on to the next step.
3. Check the connection of the power cord on both ends. Verify that the power cord is securely 
plugged into both the AC outlet and back of the computer. Does the iMac power on now? Yes: You may have a loose fit to your power cord. Replace the AC power cord and test.
No: Go on to the next step.
4.  Remove and reinstall the SO-DIMM memor y modules, located in the bottom of the 
computer. Does the iMac power on now?
Ye s: Issue resolved.
No : Go on to the next step.
5. Plug a bus powered FireWire device in like an iPod using a FireWire cable or other FireWire 
drive or device with a power LED. Does the iPod show charging or the FireWire device show a 
power LED on? Yes: The AC Power Inlet is good. Go on to the next step.
No: AC power is not being detected. If you’ve verified the outlet and power cord, replace the 
AC Power Inlet.
6. Plug a bus powered USB device into the USB ports on the rear of the computer like a keyboard, 
iPod Shuffle or USB 2.0 iPod using a USB cable and press the power button. Does the iPod show 
power or the keyboard caps lock LED light? Yes: The Power Supply is functioning. Go on to the next step.
Yes, but only for a moment: The Power Supply cannot maintain power; replace the Power 
Supply.
No: The Power Supply has failed. Replace the Power Supply.
7. At this point in the Power On process, you should hear a boot chime and see the front LED on  
						

							iMac (20-inch Late 2006) Troubleshooting — Symptom Charts 15 8
the computer light up. When the main logic board and LCD panel communicate to deliver video, 
the front LED should go out. Does the Front LED go off?
Yes: The LCD and main logic board have communicated. If there is no picture on the display, 
follow No Video troubleshooting.
No: Your logic board is not communicating with LCD panel. Open the unit and re-seat the 
TMDS cable and test again. If the issue persists, replace the main logic board.
No Video
No Video, No Boot Chime, White LED ON (Symptom 1)
The iMac will turn on (indicated by the front LED ON), but there is NO boot chime and No Video 
on the display. The faint sound of the fans, hard drive, and optical drive may  also be heard.Reset the SMC (Formerly SMU).
1.  
Turn off the computer by choosing Shut Down from the Apple menu, or by holding the 
 
-
power button until the computer turns off.
Unplug all cables from the computer, including the power cord.
 
-
Wait 15 seconds.
 
-
Plug in the power cord while simultaneously pressing and holding the power button on 
 
-
the back of the computer.
Let go of the power button.
 
-
Press the power button once more to start up your iMac.
 
-
Does the computer display video after successfully resetting the SMC?
Yes: Problem solved.
No: Continue to next step.
2.     Verify that only supported SDRAM memory has been installed and that it has been installed 
correctly. Unsupported and/or defective memory can prevent the iMac from booting. It may be 
necessary to install known good memory for testing purposes and replace any unsupported or 
defective SO-DIMM’s identified during this process. Does the computer display video after verifying and/or replacing the memory with known 
good memory?
Yes: Problem solved. Verify full system functionality before return the system to the customer.
No: Replace the logic board.
No Video, Boot Chime heard, White LED ON (Symptom 2)
The iMac will turn on, the boot chime can be heard, a white LED appears on the front bezel and 
sounds from the fan or drive activity can be heard, but the display has no picture or color.  
1. Check if the computer is sleeping. Press the space bar to wake the computer from sleep mode. 
Did the computer wake from sleep? 
						

							iMac (20-inch Late 2006) Troubleshooting — Symptom Charts 15 9
 Yes: Put the computer to sleep from the Apple menu and wake the computer again to test. 
Check Energy Saver setting to see when the computer has been designated to sleep.
 No: Continue to next step.
2. Reset your computer’s PRAM (Parameter RAM): If your iMac is on, turn it off by holding the power button until the unit powers off. You 
 
-
should hear the fans go quiet.
 While the computer is off, with your left hand, hold down the Apple key, the Option key 
 
-
next to it, and the letter “R” key on the keyboard. When you have these keys all pressed 
down, push the power button with your right hand and then quickly move that hand 
to hold down the letter “P” on the keyboard. Keep these four keys pressed while the 
computer starts up.
 Make sure you hold down the four keys (P - R - Apple - Option) while the computer is 
 
-
starting up. When you hear the computer’s start up chime for the second time, you can 
let go of the keys on the keyboard.
 If you didn’t hear at least two startup chimes, go to the top of this section and begin 
 
-
again. It’s important that you hear two startup chimes when performing this procedure. 
This indicates that you have successfully reset the computer’s PRAM (Parameter RAM).
3. Does the computer display video after successfully resetting the computer’s PRAM? Yes: Restart the computer from the Apple menu and make sure the computer is now 
working correctly.
No: Continue to next step.
4. Make sure the machine is powered off; power off the machine by holding in the Power Button 
on the rear of the machine. Turn on the machine. Observe the white LED on the front bezel 
during startup; it should go out after a few moments. Did the LED go off?  Yes: If the LED went off, this indicates that the main logic board has communicated with the 
LCD display for video signal and your main logic board should be good. You can confirm by 
connecting an external monitor and checking to see that you have video out. Go to Step 8.
No: Continue with the next step to reset system power management (SMC).
5. Reset the SMC (Formerly SMU). Turn off the computer by choosing Shut Down from the Apple menu, or by holding the 
 
-
power button until the computer turns off.
Unplug all cables from the computer, including the power cord.
 
-
Wait 15 seconds.
 
-
Plug in the power cord while simultaneously pressing and holding the power button on 
 
-
the back of the computer.
Let go of the power button.
 
-
Press the power button once more to start up your iMac.
 
-
Does the computer display video after successfully resetting the SMC?  Yes: Press and hold the power button until the computer powers off. Start the computer  
						

							iMac (20-inch Late 2006) Troubleshooting — Symptom Charts 160
again and confirm that front LED is reliably going off. If the computer still has no video but 
the LED is reliably going off, continue with step 8.
 No: Go to the next step.
6. Unplug the iMac   and remove the SDRAM. Replace with known good SDRAM. Plug the iMac   
back in and power the unit on. Does the front LED go off after a few moments now? Yes: Replace the original SDRAM and test again. If the front LED does not go off with the only 
the original SDRAM installed, replace the SDRAM. If the LED is now reliably going off after a 
few moments, but yet you still do not have any video, go to step 7.
 No: If the LED remained on, the main logic board is not communicating with the LCD panel 
to generate video. Replace the main logic board.
7. With the LED going off, you may have a No Backlight condition or an LCD failure. In a dim room, 
turn the display at an angle to you and look closely at the display. Is the display completely black 
or can you see a dim, purplish light or glow to the display? Completely black: Replace the inverter
 
-
Dim purplish light or glow: Replace the LCD panel.
 
-
Video Distortion After Waking From Sleep
Shimmering, Vertical Lines, Horizontal Lines
The iMac will wake from sleep, but a slight shimmering of the image may be visible. In some 
cases the shimmering on the display may worsen so that the display fills with vertical lines, 
horizontal lines, or the image begins to shake (refer to the following four images samples.) 
Continue with the procedure to correct the issue.