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

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My iMacs display turns off or whont turn on :(

Just about two days ago my son was using our iMac to do his homework and in the middle of him doing his paper the display when black, the back light of the display is on but the screen remains dark and I do hear the sound and fans like normal when I reboot my computer just no display. Some times the display will come on but than after about 3 minutes the display would go dark with no images just sound, any ideas of what going on? By the way when I reboot it every time I do hear the chime if that helps thanks again

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No display, just a plain black screen with no backlight just sounds, but I did check the diagnostics LEDs and I only get the 1 and 2 lights to turn on

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Well I desided to take it to the apple store, and they told me that it could be the logic board and that it may cost me about $700 or the video card and that will cost me about $100, I'm hoping it's the video card :)

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So it ended up being the video card, it's Just going to cost me $170 :)

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To help isolate the issue, please hook it up to an external monitor and let us know what you get. You say the backlight is on, can you see the desktop at all? What color is the screen?

UPDATE - added because it was to long for a comment

Check the seating of your video card

Here's the skinny on reading the LED diagnostic lights:

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

LED #1 + LED #2 + LED #3 = Power available, system is powered on, and video card found.

If third LED is not visible after power on:

• Verify that MXM video card is seated properly

• Verify logic board

LED #1 + LED #2 + LED #3 + LED #4 = Power available, system is powered on, video card found, and internal LCD found.

If fourth LED is not visible after power on:

• Verify cable connections between LCD panel and logic board

• Inspect LCD display cables for cable damage

• Verify external video functionality, and according to result check the following items:

-If external display works then verify/replace LED backlight board

-If external display works then verify/replace LCD panel

-If external display does not work verify/replace logic board

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No I can't see anything,all I see is a lighted blank dark gray screen and if it help I do here the chime when I re start my iMac every time, I'll try hooking it up to an external monitor I just need to get one

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Can you still see the desktop dimly?

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I have an iMac 24 from mid 2008. The system run OK this morning. then in the middle of running an application, the LCD screen went compeltely dark. but the computer is still on and running the application because it chimes during key sequence input. I am sure it will play iTunes if I run it too.

I turned it off and then reset the SMC and turned it back on. It chimed during power up and i can hear the thrashing of hard disk and Superdrive which shows the posting and bootup are working. But it took 15 minute for the display to come back on. I left it on and idle overnight. Then this morning i ran some applications. The same problem recurred.

The cause of this being a video card is unlikely. Video card problems generally are more severe and will cause the system to crash, display distortions, lines, etc. But it is possilbe it is the video card.

More likely, this is an LCD screen issue, and possibly issue with the backlight. The latter seems to lose power sunddently, possibly due to some shorting. But the backlight itself does provide plenty of light when the display is on and shows video.

I dont know if it is

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miguel fernandez will be eternally grateful.
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