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

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iMac could not start. Only LED1 is on.

LED1 on my iMac is on. When I press power button, LED1, LED2 and LED3 light up, but only for half a second and then all LEDs turn off.

When I unplug AC power and plug back in, the LED1 is again light up. What can I do?

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Here's a breakdown on what the diagnostic LED conditions are:

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.

I would first try replacing the power supply or test the DC voltages are present and correct on the main logic board header from the power supply using a volt meter.

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Thank you for quick reply.

I suspect the power supplt also, but I dont have any reference guide which header pin is which. Do you have some reference?

I think it is this supply: iMac 24" E'09 A1225 Power Supply 250W 661-4995 614-0432 PA-3241-02A2 ADP-250AF B

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