Start by resetting your SMC. On this system you do that by unplugging the system for 30 seconds. To ensure all the capacitors are drained of their power you might hold down on the power button for 10 seconds during that time. The mentioned times are not extremely critical. Resetting the SMC could solve your problem.
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Start by resetting your SMC. On this system you do that by unplugging the system for 30 seconds. To ensure all the capacitors are drained of their power you might hold down on the power button for 10 seconds during that time. The mentioned times are not extremely critical. Resetting the SMC could solve your problem. The second thing I suggest is hooking it up to an external monitor. If you have a picture there the problem is most likely the LVDS cable or LCD. I have not heard you mention anything about if it chimes or not at boot???
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If it doesn't there are four built-in diagnostic LEDs on the main logic board that can help you to troubleshoot the computer. The LEDs are located on the bottom left edge of the logic board (under a piece of black mylar tape) and can be seen when looking through the lower vents of the enclosure. LED 1 is located furthest to the left.
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There are four built-in diagnostic LEDs on the main logic board that can help you to troubleshoot the computer. The LEDs are located on the bottom left edge of the logic board (under a piece of black mylar tape) and can be seen when looking through the lower vents of the enclosure. LED 1 is located furthest to the left.
[image|144929]
'''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.
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If no LED is visible:
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• Verify AC source
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• Verify known-good AC cable is connected
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• Verify cable connection between AC inlet and power supply
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• Verify cable connection between power supply and logic board
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• Verify power supply
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'''LED #2'''
• Indicates that the main logic board has detected proper power from the power supply when the computer is turned on and that logic board voltage regulators are functioning properly. This LED will be ON when the computer is turned on and the power supply is working correctly.
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If LED 1 is lit and second LED is not visible when power button is pressed:
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• Verify power button connection to logic board
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• Verify power button functionality
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• Verify cable connection between power supply and logic board
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• Verify power supply
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• Verify logic board
'''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.
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If the first 2 are lit and third LED is not visible after power on:
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• Verify that the MXM video card is seated properly
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• Verify logic board
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'''LED #4'''
• Indicates that the computer and the LCD panel 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 image on the display, then the LCD panel, the LED backlight board, or the cables between might be installed incorrectly or need replacement.
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If if the first 3 are lit and the fourth LED is not visible after power on:
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• Verify cable connections between LCD panel and logic board
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• Inspect LCD display cables for cable damage
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• Verify external video functionality, and according to result check the following items
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-If external display works then verify/replace the LED backlight board
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-If external display works then verify/replace the LCD panel
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-If external display does not work verify/replace the logic board
Start by resetting your SMC. On this system you do that by unplugging the system for 30 seconds. To ensure all the capacitors are drained of their power you might hold down on the power button for 10 seconds during that time. The mentioned times are not extremely critical. Resetting the SMC could solve your problem.
If it doesn't there are four built-in diagnostic LEDs on the main logic board that can help you to troubleshoot the computer. The LEDs are located on the bottom left edge of the logic board (under a piece of black mylar tape) and can be seen when looking through the lower vents of the enclosure. LED 1 is located furthest to the left.
[image|144929]
'''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 and that logic board voltage regulators are functioning properly. 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.
'''LED #4'''
• Indicates that the computer and the LCD panel 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 image on the display, then the LCD panel, the LED backlight board, or the cables between might be installed incorrectly or need replacement.
Please tell us the results of the fore mentioned.