原帖由： oldturkey03 ,
@rms8 the very first thing you want to di is tell us what your diagnostic LED's are showing you. 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: 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 diagnostic LEDs 1, 2, and 3 are 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. [image|772141] 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. 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. To check the voltafge you may want to consider checking [guide|2740|this great guide.] Slightly younger model, but should still prove valuable.