3 
1 A1267 ACD 24" backlight issue
About two years ago I was playing a video game on my Mac Pro, although it was a low-end GPU, I was rendering the game on high graphical settings. The fans in the processor started revving up and making frighteningly loud noises. Then without warning the screen just shut off. From that moment I found that the display would not work unless I reduced the brightness below 10/15 increments. This got worse over time and now it only works on the lowest brightness setting. Shining a flashlight at the LED screen reveals a faint image when the display goes black. This suggests that the backlight is the issue. I carefully removed the glass, LCD screen and had a look at all the components inside. I'm no electrical engineer, but the Power Supply board and Logic board look fine to me (no swollen caps or burnt areas). I tested the voltage on the test points on the Logic board and it all reports fine.
From here, I don't know how to proceed troubleshooting this problem. It's always evading my attempt to fix it. The best way to troubleshoot this problem would be to temporarily swap identical model components to isolate what is the source of the problem. But I'm living in an area where nobody has a ACD. I've tried bartering with ACD sellers on online marketplaces to no luck. There are six main physical components inside the monitor that are culprits, replacing each on the off-chance would cost a collective ~€300 if I was unlucky.
Images: http://imgur.com/a/09iOx
Update (01/20/2017)
Dan,
I've read the service manual carefully several times but I can find no solution and I've read every answer to the backlight issue on fixit but find no solution.
I've taken apart and reassembled every component inside the monitor with the exception of the main driver cable leading directly into the monitor. It was covered with weird silver tape (electrical tape?) that had to be peeled back. But I haven't had the guts to attempt to remove the cable from the slot, as it doesn't seem to want to come out. Does anyone know how to remove this cable?
Images: http://imgur.com/a/i3JUs
Update (04/25/2018)
I have an update 13 months since my last post. The brightness in my display eventually gave out entirely and just didn't boot up at all when I powered on the processor. But then to my surprise the processor also stopped booting! Which implies the problem was with the processor all along.
Anyway, I bought a replacement graphics card and PSU individually, and neither part solved the issue. I cleaned the inside thoroughly and made sure everything is connected and such.
I am not done with the problem. I have not yet found a solution. My current focus is on the backplane board as I have ruled out almost everything else.
Occasionally the processor boots after an attempt to power up, with the display flickering for a moment and then going black.
Questa è una buona domanda?
973 
21 Commenti
See if this helps: The service manual
da Dan
As explained in the original post I checked the voltage on all the test points on the logic board and they all report fine. Initially I presumed the issue was with the GPU, but after buying a new GPU I can confirm that is not the issue. I replaced the main power cable too, but no change. The firmware is updated, so I'm fairly confident it's not a software issue.
da Morgan
Is there any help you can offer me?
As explained, the inner components pass the inspection test. I don't want to shell out €220 on a new logic board in the hope that that is the source of the problem. What if it isn't - I've wasted a lot of money.
da Morgan
Did you download the file in the link above? Review the section on display for all of the details.
Can't offer you more without doing the tests as outlined in the doc. If you can't do it thats fine, you'll need to find someone in your area to help you.
Once you've isolated things you might be able to get someone to fix the logic board or you'll need to replace the part as needed.
da Dan
Yes I've read the service manual top to bottom several times and I'm all out of ideas. I've followed the chain of solutions but they've been no help. The Logic board looks fine on visual inspection, and the voltages are correct. The Power supply unit looks fine too. The cables are all seated correctely. The one cable I'm unsure of is the cable leading directly into the monitor. I've been too cautious to attempt to remove it by yanking it out. It doesn't seem to want to come out. I would like to replace that cable if I could but it's the most difficult individual component to purchase on an online marketplace. Not that it matter anyway because I'm too afraid to remove it and don't even know if it's meant to come out.
da Morgan
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