iMac Powers Up, Black Screen and Not display at all

Hi,

I had this iMac 24" A1200 which has defective Video card. The computer has worked but has pixels and artifacts when using a little bit of graphics.

I had send the VGA card for a reballing and we change the GPU and when it comes back, the iMac show LED1 OK; LED2 OK; but LED3 and LED4 are not lightning.

The iMac has open; black screen and the power button is "ON". All fans are working in maximum and something is not working properly.

I had purchase another video card which i think its that the problem, but the video card has the same results.

The video card which i purchase, it come from another "iMac" which is the logic board capacitors is defective, the pc was just rebooting.

Samething.

Now i would like to know, what can i do more? i've try SMD reset, nothing happen.

No chime. All capacitors on mine is look good (no bursted capacitors).

Can something get wrong with the logic card?

Answered! View the answer I have this problem too

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My iMac has same problem. Could you share your comments if you already fixed yours? Thanks

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How about creating your own question as this is such an old question to carry forward

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Chosen Solution

Connect to an external monitor. If you see normal video the problem is part of the internal display chain.

LED #3 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 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 LCD display panel, the LCD display panel or inverter might be installed incorrectly or need replacement. If the LED is off points back to the GPU.

If this answer is acceptable please remember to return and mark it.

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Stephane Robert will be eternally grateful.
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