Diagnostic LEDs
The iMac has three built-in diagnostic LEDs and a front LED on the main logic board (shown below) that can help you to troubleshoot the computer.
To Access the LEDs:
1.Follow the take apart instructions to remove the RAM access door, front bezel, and lower EMI shield.
2.Locate the SO-DIMM slot and LVDS video connector. The three troubleshooting LEDs 1, 2, and 3 are located to the right of the LVDS cable connector, under a square of black tape. Peel back the tape to view the LEDs. Note that the LEDs are marked 1, 2, 3 from left to right, as show below. An additional front LED is located in an opening at the center of the right speaker, as shown below.
iMac (17-inch Mid 2006/Late 2006 CD) Troubleshooting — General Info 125