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iMac Intel 27" EMC 2309 (Late 2009, Core 2 Duo 3.06 or 3.33 GHz) ID iMac10,1, EMC 2374 (Late 2009, Core i5 2.66 GHz or Core i7 2.8 GHz) ID iMac11,1

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iMac 2009 black screen no chime

Hi - I bought a 27in 2009 iMac from an auction site cheaply to repair. The owner said it beeped every few seconds, which made me believe it could be as simple as the RAM not being seated correctly. No such luck. I did replace the RAM and the beep went away but the screen remained black, with no boot chime. I lifted the LCD away and it briefly lit up (which has subsequence done a couple of times but only fleeting). Oddly when pulling the LCD away, the PSU, or inverter board start buzzing at varied speeds based on the distance the LCD is away. I convinced myself it was the inverter flex ribbon cable, which had seen better days, so I replaced but with no joy. I have tried different RAM and fortunately have a working model, so switched out the PSU, inverter board and LCD, again to no joy. The only remaining choice is the logic board, video card, or a loose connection. I can’t get an image on an external display either. I just wondered if any iMac geniuses might have any insight. I’m still not convinced it isn’t the PSU and inverter board.

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whats does the leds on the logic board show you, it can give you some idea of faults

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Jonathan just like daniel commented, check your diagnostic LED's. The iMac (27-inch, Late 2009) computer has four built-in diagnostic LEDs on the main logic board that can help you to troubleshoot the computer. The LEDs are located on the bottom left edge of the logic board (under a piece of black mylar tape) and can only be seen when looking through the lower vents of the enclosure.

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LED 1 is on the right hand side

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 and that logic board voltage regulators are functioning properly. 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 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 display, then the LCD panel, the LED backlight board, or the cables between might be installed incorrectly or need replacement.

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 the 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 the LED backlight board

-If external display works then verify/replace the LCD panel

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

Next you can check a few things on your logic board. Some test points are accessible on the logic board when the LCD panel is removed. The test points are defined below.

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After that, you may need to give the Apple symptoms chart a going over. See what you come up with and let us know. Symptoms Chart

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Jonathan zal eeuwig dankbaar zijn.
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