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iMac (24-inch Mid 2007) Take Apart — General Information 209
Diagnostic LEDs
The iMac (24-inch 2007) has four built-in diagnostic LEDs on the main logic board that can help
you to troubleshoot the computer. The four LEDs are located to the right of the memory slot. It
may be necessary to carefully move the hard drive data cable to view the LEDs.
To Access the LEDs:
Follow the take apart instructions to remove the memory 1. access door and front bezel.
The four troubleshooting LEDs 1, 2, 3, and 4 (numbered bottom to top) are in a column 2.
located to the right of the memory slot. Move the hard drive data cable to view the LEDs.
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 (24-inch) 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 o 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.
LED #3
Indicates that the computer and the video card are communicating. This LED will be ON •
when the computer is communicating properly with the video card. If LEDs 1 and 2 are ON
and you heard the startup sound, but LED 3 is OFF, then the video card might be installed
incorrectly or need replacement.