The ¡Mac (24-inch) has four built-in diagnostic LEDs and a front LED on the main logic board that can help you to troubleshoot the computer. The four LEDs are located to the right of the memory
• 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 off only if the AC power source is disconnected or the power supply is faulty.
• 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.
• 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.
• 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. If the LED is ON and there is no display on the panel, the panel or inverter might be installed incorrectly or need replacement.
• 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.
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