Late 2009 27" iMac will not power up
iMac will not power up. Fan seems to start.
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John Celano start with this:
The iMac (27-inch, Late 2009) computer has 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 only be seen when looking
through the lower vents of the enclosure.
• 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.
• 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
• 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 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.
Let us know what you get on your iMac.
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