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

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Display dark after HD swap. LEDs #3&4 off. Checking cables/connectors?

My 24" 2007-8 iMac and display worked fine until I did a hard drive replacement, following an excellent iFixit guide judiciously. The new hard drive works find, but the display never fired back up. I've gone in and done a few diagnostics (below), but before I put the iMac out to MacPasture, I want to go in one last time and check all the cables and connections for continuity with my meter, in case it's something from the work I did. BUT...

1. Just for grins, let's first assume that it's not a fried logic or graphics board, but is a cable that was broken, or a connector, or a cable was put in backwards, etc. Based on the following symptoms, which cable/connector thing(s) should I be looking at as a culprit?

  • I've gone in once and made sure all the connections are solid.
  • I can see the hard drive via target disk mode.
  • An external monitor does not work.
  • LED diagnostic lights #1 and #2 are on, but #3 and #4 are off.
  • I was careful on static discharge always.

2. This isn't where I wanted to go, but how do I check to see if it's a bad logic board, graphics board, or something else?

Thank you very much in advance for any help.

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Check your connections to the video card.

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 (turn on and remain 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 (turn on and remain 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 (turn on and remain 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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