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

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Powers ON, Chime, Black Display but external monitor shows video.

Hello,

I have a 24" iMac 2007 2.4GHz which turns ON to a black display. I have done a lot of research and have looked at many guides to determine the exact issue and fix. I will explain everything i have done to troubleshoot but without a resolution.

Below you will see my troubleshooting has confirmed that both the Video card is in working order and the LCD screen is in working order.

I have hooked up an external display and turned ON the iMac and to my surprise I was able to see video on the external display. So this means my graphics card is in working order.

I removed the glass and aluminum frame and looked at the 4 LED lights and when powered ON all of the 4 LED's are solid green. So that means everything is communicating with each other like Power Supply, LCD Screen, Video card and Motherboard.

I decided to swap the LCD screen out with another iMac that i own (same EXACT model, specs and year iMac & same model # LCD screen). To my surprise the LCD remained black when i turned ON the iMac. This is a known good working LCD screen since it was removed from a fully functional imac. So i decided to swap the original screen from the 1st imac that doesnt display to the fully functional imac and i was able to see video on that screen. So now i know the actual LCD is in working order too!

At this point i am stuck and dont know what the issue is and what more i can do.

I was able to determine the Video card to be in working order by using an external display and i was able to confirm the LCD works by swapping it into another iMac system.

What else can i try to troubleshoot it in order to get this iMac to work again?

Please help me

Thank you

Answered! View the answer I have this problem too

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Is it a backlight problem? If you hold a flashlight up to it can you faintly see the image on the screen? It takes getting just the right angle of the light and your view sometimes.

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I dont think it has anything to do with the backlight or the LCD screen since i was able to swap the screen into another imac and verified the screen is in working order. I even placed a known good working LCD from another imac into it and it still didnt show picture.

Based on having a working LCD screen i dont think the screen is bad nor the backlight.

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I was thinking it may be the power supply circuit to the LCD. Lucky you have another iMac for parts testing! Try borrowing the Power Supply from the other iMac and see if that sorts it.

Another random idea would be to put it to sleep and wake it. I once saw an iMac that would only engage the LCD after waking. Probably not, but hey, worth a shot. Happy repairs!

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Deck the Halls
With tools and Fix Kits

2 Answers

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If you can see a faint image on the LCD then the backlight circuit is having problems. This problem won't show up under the diagnostics LED's on the logic board as it's an independent circuit.

Your system uses CFL's so it needs a high voltage (250 volts) to drive the tubes. Here is the needed IFIXIT guide to replace the faulty Inverter: iMac Intel 24" EMC 2111 Inverter Board Replacement.

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The LCD assembly worked fine on his second iMac, so that would rule the inverter out. Its worth testing with your other power supply before ordering the part.

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@ToupeeScalper - The inverter is not part of the display unit. He took the good display and put it into the bad unit which points the to the Inverter.

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@Dan - iMac #1 is the one which is not displaying anything on the LCD screen. iMac #2 is a fully functional iMac which is the same model/year & specs. I removed the display assembly from iMac #2 and placed it into iMac #1 which didnt do anything. So now i decided to put the original LCD display from iMac #1 (which was suspected bad) into iMac #2 and i was able to see video. This particular iMac model A1225 (aluminum body)has the inverter installed on the back of the LCD itself (just like it shows in the 24" inverter replacement on the plastic frame model in the link you posted). So by process of elimination since i tested the original LCD into iMac #2 and it worked the LCD and inverter/backlights are in working order since the inverter board on the LCD was never touched or swapped. The entire LCD assembly was swapped.

@toupeescalper - I swapped power supply's but still having the same issue.

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@Mike @toupeescalper - I stand corrected! I had thought you had replaced the LCD only.

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@Dan - No worries, i can see how the wording could have been a little confusing. So im still back to square one trying to figure out why there isnt a display.

I also tried switching LVDS cables and inverter power cables still with no change.

Is it possible the actual LCD port on the MB went bad? If the port went bad would the LED lights still confirm communication? Or is the port working since the LED's are lighting up confirming communication with the LCD display and video card?

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I have the same problem

Same model can't find a solution anywhere

All these super smart people and nothing out there

Did you ever find a solution??

Update (08/30/2017)

Its the GPU gone bad despite getting for lights on the logic board

I had the exact same problem

Searched and searched for an answer (found nothing)

Replaced the display, inverter cable, and then the logic board.

When that didn't do it I had an extra GPU that closely matched the GPU in the iMac and

now I am using a fully functional (despite a yellow screen which is another story) to write this post

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@dennisb - How about creating your own question with your details as most likely your info will offer a clue why your system is having problems.

Mike was having problems swapping displays between systems so his problem is most likely not the same and I suspect you have a different model as well.

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No same problem Mike was trying to get his display to work with his 2007 iMac 24 inch same model as mine. He tested the display by swapping them out with another iMac. The display worked in one iMac not the other. He also tested the non working iMac with an external display. I have replaced the power supply the inverter power cable even bought another display same problem. Have you ever heard of a power supply powering the computer but not the display??

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I`ve got exactly same problem as Dennis Boniphant "No same problem Mike was trying to get his display to work with his 2007 iMac 24 inch same model as mine. He tested the display by swapping them out with another iMac. The display worked in one iMac not the other. He also tested the non working iMac with an external display. I have replaced the power supply the inverter power cable even bought another display same problem. Have you ever heard of a power supply powering the computer but not the display??"

I`m tired of this problem!!! Please Help!!!

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Mike will be eternally grateful.
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