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Model A1174 with 2 GHz Core Duo or Model A1207 with 2.16 or 2.33 GHz Core 2 Duo

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Why do I see only one diagnostic LED lighting up?

IMac model A1027

Hello, I have a iMac model A1207, after a power surge, it could no longer start up, no sound or picture! (It was plugged into a power surge protector) I assume it is the power supply! I opened up it up and check it out while powered. There are three LED lights. Only number 1 (LED 601) is lit up when the power cable is in, when I press the power button, no 2 (LED 602) flickers briefly, but does not stay on! No. 3 (LED 603) never comes on!

When I turn on the power button I see the left fan turns slightly! But then stops!

I would really like to find the cheapest way to fix this computer, if repairable.

Any ideas! I have read the generic description of the meaning of the LED lights, but I would appreciate a more specific opinion! If possible.

Thank you so much for your time!

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Hi, thank you very much, I used the guide, replaced power supply! Now Led no 1 and 2 light up and stay on, number 3 is still not lighting up! Screen when you switch it on is black and the power on LED on the front bottom right is shining! Also no chime! Any ideas what to try next?

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Replace the power supply. Here's how: iMac Intel 20" EMC 2105 and 2118 Power Supply Replacement

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.

LED Startup Sequence

LED #1 = Power available.

If no LED is visible:

• Verify AC source

• Verify known-good AC cable is connected

• Verify cable connection between AC inlet and power supply

• Verify cable connection between power supply and logic board

• Verify power supply

'''LED #1 + LED #2 = Power available, and system is powered on.

If second LED is not visible when power button is pressed:

• Verify power button connection to logic board

• Verify power button functionality

• Verify cable connection between power supply and logic board

• Verify power supply

• Verify logic board'''

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And if de second led just blink twice when pressing de power button?

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