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...

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...

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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.
•...

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...

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...

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...

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....

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...

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...