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

468 Questions View all

No Backlight No Display 3 Diag Lights on

I purchased this iMac with the intention to repair to sell for more. I have some Ideas that it may be the logic board or just a bad video card.

When the unit is off and the power cable is in, LED #1 is lite, during start up LED#2 and LED#3 light up and all three lights stay on. I then hear the Macintosh chime. After giving the system a chance to boot up (fans running, hard drive is working) I can press play and listen to my iTunes library no problem...except I can't see the screen. Nor an image or back light on the internal LCD, with hopes of it just being a bad LCD I connected it to my TV via Mini DVI>DVItoHDMI Converter>HDMI Cable. I was unable to receive an image on the screen, is it possible it's the crazy cabling or bad video card? Bad logic board? I'm Stuck on this one, I consider myself a fairly techy guy but this one I need help confirming before attempting to fix or deciding to sell.

Things I have tried thus far:

I attempted to reset the PRam, after first reset the startup chime is now louder.

I checked and re-seated the ram, changing slots.

If this was possible I did a SMU/SMC? without opening by removing the power cable from behind the unit, waiting 15s secs, holding power for 5 seconds, then plugging back in, then powering on.

Answered! View the answer I have this problem too

Is this a good question?

Score 0
Add a comment

2 Answers

Chosen Solution

Before making a call on this one, I'd like to see you hook up to an actual monitor.

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.

Was this answer helpful?

Score 4


@Mayer I did attempt to try and connect to it a actual monitor and unfortunately didn't get a response or display out. If I read correctly if the 4th LED light never lights up this means the LCD has not been detected or not receiving power?


The lack of a image on your external monitor indicated to me that a video signal is not being generated. Try reseating the video card, examine it for any burned areas.


Add a comment


I have exactly the same problem, the difference is that i have an iMac intel 20'' 2007. With this difference there ir no independent graphics card, so i can't replace it. Wish it's not all the logic board.

The first 3 LEDs are on but the 4th never turns on.

Any suggestions?

ty in advance

Was this answer helpful?

Score 0
Add a comment

Add your answer

Truman Boone will be eternally grateful.
View Statistics:

Past 24 Hours: 0

Past 7 Days: 1

Past 30 Days: 5

All Time: 2,797