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No video, no chime

I am working on a customer’s 24” iMac 2007. I have no video and no chime when I turn it on. Have reset PRAM and SMC. LEDs 1, 2 and 3 light up, but not 4. I believe the RAM is good but I can’t be for sure. Also connected second monitor and get nothing there.

Suggestions? Thoughts?



Répondre à cette question J'ai le même problème

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Are you getting any feedback at all when you try to boot up? How do you know that the PRAM and SMC reset was successful if there's no chimes? I would follow the line of failure step by step. Is the outlet good? is the cable good? (check with a multimeter) if both yes, maybe the PSU is dead? Or perhaps something simple like the power button is broken/malfunctioning.


What does an external monitor show? Also see if shining a flashlight into the display at a sharp angle if you can see the faint image of your desktop and its icons.


I will clarify. The fan spins up and I can hear the hard drive, No video or chime. I have attempted to reset the PRAM but I get nothing there either and the keyboard seems not to be responding as the caps key will not light up. The outlet is good and the cable is good.


I get nothing on the external monitor. As well, the screen is totally dark when I shine a light on it.


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Something is not right here as the onboard diagnostic LED’s are telling us the GPU is working, yet you also state the external monitor is not showing an image.

So we either have a bad display or we have a bad logic board.

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I was thinking logic board, too. Any way to test the LCD or logic board to rule out one or the other?


Yes, but somehow in this part of the space continuum 4 + 4 equals five here!

So you'll need to double check your tests as the math doesn't add up correctly ;-}


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shull check this as well


No Video, No Boot Chime

The computer will turn on, but there is no boot chime and no video on the display. The faint sound of the fans, hard drive, and optical drive may also be heard.

1. Make sure all software updates have been applied to the computer. Refer to KBase article 303903, Intel-based iMac: Installing available updates , and to Apple Downloads for updates for the iMac (Mid 2007) model of computers.

2. Follow instructions in the “General Information” chapter to reset the SMC. Does the computer display video after successfully resetting the SMC?

Yes: Problem solved.

No: Continue to next step.

3. Verify that only supported SDRAM memory has been installed and that it has been installed correctly. Unsupported and/or defective memory can prevent the computer from booting. It may be necessary to install known good memory for testing purposes and replace any unsupported or defective SO-DIMM’s identified during this process. Does the computer display video after verifying and/or replacing the memory with known good memory?

Yes: Problem solved. Verify full system functionality before return the system to the customer.

No: Replace the logic board. (don’t do that just yet ;-)

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 (24-inch) 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. 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 or inverter might be installed incorrectly or need replacement.

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shull sera éternellement reconnaissant.
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