Model A1225 / Mid 2007 and Early 2008 / 2.4, 2.8, or 3.06 GHz Core 2 Duo processor

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Won't Boot, 3 LEDS on, NO fans or HD, only optical works

iMac Intel 24" EMC 2134

Hello, I have been having a really hard time coming up with a diagnosis for this problem. I can't seem to find anybody with the same set of issues. When I turn the power on, the only thing that seems to kick in is the optical drive. The fans don't even move and the hard drive doesn't spin. There is no chime. The first 3 LEDs light up, but not the fourth. I tend to think it must be the logic board but I'd like to be sure. It seems odd to me that it has so little life despite first 3 diagnostic LEDs being on. I tried re-seating the RAM, and using only 1 stick then only the other. Any ideas?

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I ended up replacing the logic board but the problem remains. Does anybody know if these problems are consistent with a dead CPU?

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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 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 display 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 LCD display panel, the LCD display panel or inverter might be installed incorrectly or need replacement.

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