iMac 2006 No picture but GPU and LCD are OK


I have got a working iMac 24 a1200. Everything is OK GPU /LCD are perfect.

Now I bought a dead iMac 24 a1200 on ebay. It shows no picture but the fans are turning on and the white led is on, but the LCD doesn't show any picture.

When I turn on the iMac the start tone appears and the backlight turns on but the pixels stay black (black with little glow behind). I connected the iMac to another monitor - no input.

So I swop the LCD out of the ebay iMac and installed it in my working iMac 24. It worked - so the ebay LCD must be OK.

After that I turnd on the ebay iMac without the LCD but connected to an external monitor. The iMac started nornaly and showed a perfect picture on the external monitor. So the GPU is fine.

By the way all 4 control leds are turnd on when the iMac is runnig.

What could be the problem? Is it a logic board defect? Why is the GPU not communicating with the LCD?

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Can you discern the desktop, when it is on, and shinning a flashlight at an angle to the screen.


Thank you for your reply! I will try that.

But I am sure that the backlight is working because, when I turn the iMac on there is a gray shine behind the pixels.

Is it possible, that the logic board has a communication problem between the GPU and the display/lvds connector? But if there is an communication problem, why does it work with an external display?


What are the diagnostic LEDs to the right of the RAM slots telling you?


They are all running!


Examine the capacitors (small cans) for swelling and/or leakage.


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