Model A1225 / Mid 2007 and Early 2008 / 2.4, 2.8, or 3.06 GHz Core 2 Duo processor

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screen nothing can be seen it's completely black

Hello there, I know this thread is a little more than 3 years old, but my iMac 24" A1225, 3.06GHz just got into the same problem. It can only display video on external display and works just fine, I already pointed a flash light directly into the screen but nothing can be seen it's completely black. The one different thing about mine is that despite the screen is black and external display is displaying video all four leds are lit while on. Does anybody has gone trough this and has found a solution for it?

Your response will be greatly appreciated. Thank you in advance.

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MACAT, could be a bad inverter or inverter cable. Check what Apple says first:"

No Video, Boot Chime Heard

The computer will turn on, the boot chime can be heard and activity from the fan or drive can be heard, but the display has no picture or color.

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 all available updates for the iMac (Mid 2007) model of computers.

2. Check if the computer is sleeping. Press the space bar to wake the computer from sleep mode. Did the computer wake from sleep?

Yes: Put the computer to sleep from the Apple menu and wake the computer again to test. Check Energy Saver setting to see when the computer has been designated to sleep.

No: Continue to next step.

3. Reset your computer’s PRAM (Parameter RAM):

Shut down the computer.--

Locate the following keys on the keyboard: Command, Option, P, and R. --

Turn on the computer.--

Press and hold the Command-Option-P-R keys simultaneously. You must press this key --combination before the gray screen appears.

Hold the keys down until the computer restarts and you hear the startup sound for the --second time.

Release the keys.--

4. Does the computer display video after successfully resetting the computer’s PRAM?

Yes: Restart the computer from the Apple menu and make sure the computer is now working correctly.

No: Continue to next step.

5. Make sure the machine is powered off, and remove the access door and front bezel to access the diagnostic LEDs. Plug in and start up the computer to observe the diagnostic LEDs. At this point in the Power On process, you should hear a boot chime, and LED #1 and #2 are On. Is LED #3 On or Off?

LED # 3 is On: The video card and logic board are communicating properly. Go to the next step.

LED # 3 is Off: The video card and logic board are not communicating. Replace the video card. If the issue persists, replace the main logic board.

6. LED #4 should be On when the video card and LCD display have communicated properly to produce a video image. Is LED #4 On or Off?

LED # 4 is On: The video card and LCD display have communicated to produce video. In this case, there is a problem with the backlights in the panel or the inverter. Verify the inverter cable is fully inserted into the cable connector on the inverter and check that the wires have not been pinched. Replace the inverter cable first and then the LCD panel if the problem

persists.

LED # 4 is LED # 4 is Off: The video card and logic board are unable to communicate to generate video. Replace the video card and install the iMac Graphics Firmware Update. If the issues persists, replace the LCD display.

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Comments:

Thanks oldturkey03, I appreciate your response. Actually this iMac is out of warranty and to place a call to Apple is $20 dlrs. and with a tight budget wanted to save me those $20 bucks. I already did everything you suggested here but still nothing. Still same situation, iMac works with external monitor and if I go to System Report it shows that External monitor, iMac display and video card are detected an they are online and all 4 diagnostic lights are lit up green.

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Then proceed with this "In this case, there is a problem with the backlights in the panel or the inverter. Verify the inverter cable is fully inserted into the cable connector on the inverter and check that the wires have not been pinched. Replace the inverter cable first" after that you may be looking at a new inverter. also check your backlight fuse for continuity and see if you have power on it.

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Thank so much...I will do that on Monday cause I won't have any spare time until then. I will post with the result on Monday most likely. Thank you again for your quick responses.

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