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A1418 / EMC 3068 / iMac 18,1 / 2.3 GHz dual-core i5 processor. Released June 2017.

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No Startup chime or any display on screen

I put a brand new screen on my Mac and there is no display of any kind or even a startup chime anymore. It worked with the old broken screen but I no longer have it. Any ideas?

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Can you see the onboard diagnostic LED’s? What are they telling you (with the display connected)

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Here's a breakdown of the onboard diagnostic LED's:

LED 1 - Indicates that the trickle voltage from the power supply is detected by the main logic board. This LED will remain ON while the iMac is connected to the AC power. 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 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 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 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 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 might be installed incorrectly or need replacement.


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All four come on and stay on. The lcd panel is brand new and so is the lvd cable.

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@Ian McClain - OK, lets do this with the system put together restart the system and this time take a flashlight pressed against the screen at a sharp angle do you see the faint image of your desktop and its icons? If you do the backlight logic and cable needs to be checked.

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I cannot see anything even while doing this.

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@Ian McClain - So you are not getting any signals to the display.

Then we need to check things via an external display have you tried connecting one via the mDP/Thunderbolt ports either directly or through an adapter?

Are you sure you got a good display is it possible the system got more damaged than just the display?

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@danj I have not tried an external display yet and I’m pretty sure just the lcd was broke because it still lit up with the old broken screen.

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