24" Cinema Display back-light issue

Right, I've got a problem and I really need your help. I bought a Mac Pro 4,1 computer in late 2009 with a 24" Apple Cinema Display monitor. In 2013, I was playing a graphically intensive video game and without warning the screen went black. I shut off the computer at the wall, but the screen didn't light up when I booted it back up. I retried this many times, but the screen never turned on with the computer. I didn't know if the problem was with the GPU, or monitor, or some other component. Without visual accompaniment, I navigated to the Desktop and used the keyboard shortcut to reduce the brightness, and then shut off the computer. With the brightness at it's lowest setting, the screen lit up when I powered on the computer. However, another problem, the screen blinks rapidly and then shuts down, or stays on. On average,I have to power on the computer roughly 5-20 times before the screen stays on. I found that I couldn't have the brightness above 10/15 increments after that day. A few months later, it dropped to 6/15, then 3/15, and now it's on the lowest brightness setting. I've postponed the problem until now, but it has to be sorted, as the experience is hardly useable. Presuming the issue was with the GPU, I purchased a Nvidia GTX 680 recently, but the brightness issue remains. The fans on the card spin into action, and the appropriate software drivers are installed, and the power cables are plugged in, but I get no response from the monitor. This suggests to me that the problem is the monitor. The monitor is only able to power the default GPU on the lowest brightness setting, and can't power the GTX 680 at all.

So, I don't know where to go from here. I want to repair the Cinema Display monitor, but don't know how to do that, or if it's possible. It was dan extremely expensive monitor when purchased, and in my opinion is still relatively young (seven years). I don't know the anatomy of a computer monitor or how it works. Is there some part inside that can be replaced?

Could the problem be the power unit inside the Mac Pro? Do you have any suggestions as to how to further troubleshoot or solve this issue? As it stands, I can barely see what I'm doing on the computer.

Welcome to our forums.

So, I don't know where to go from here. I want to repair the Cinema Display monitor, but don't know how to do that, or if it's possible. It was dan extremely expensive monitor when purchased, and in my opinion is still relatively young (seven years). I don't know the anatomy of a computer monitor or how it works. Is there some part inside that can be replaced?

Click to expand...

You probably don't want to hear this but.... your 24" Cinema Display is a vintage display and very likely is not worth repairing. Yes, all Apple Cinema displays are expensive but you have already gotten 7 years out of it. You can replace that display with a brighter larger one for around $300.00 at the most. No, it won't be an Apple Cinema display. And by the way, Apple is no longer in the Cinema Display business and is now selling the LG 5K display on their web site instead. ($985)

If you wish to repair your display, go to www.ifixit.com and take a look at their instructions. If the backlight is defective as you think, they (ifixit) may have a recommended repair. Good luck with it.

Thanks. I checked ifixit and many people have had the same issue. I removed every component inside the display today, cleaned out dust, checked for loose cables, the capacitors look healthy to my eyes. My next step is to check the electrical charge at certain points with a digital multimeter. I honestly don't know at this point what component exactly is causing all the trouble.

I don't know if this will help or not... but some older MacBook Pro models used a fuse to protect the backlight circuit (this is for LED backlight only). In many cases of no backlight on those models, the fuse was the culprit. Your 24" Cinema Display may likewise have a fused circuit, however, I don't know that for certain. Backlight problems can be a real headache to troubleshoot because there are more than one failure types that can cause it to not function.

http://imgur.com/a/cUmLX

Some pictures.

@chscag
I think something on the Logic board or the Power supply board are responsible for the issue. That, or a bad cable. That's what I seem to have narrowed it down to.I think the clue is in knowing that the issue began when I pushed the hardware to it's limit by playing a graphically-intensive video game. It's been going down ever since that moment. So, I think I blew a fuse or something. But the capacitors look fine to my eyes. I'm not very technical.

From memory, the fuse on the MacBook Pro logic board is a tiny fuse that resembles a resistor. In other words, it looks nothing like an ordinary fuse. You couldn't have done any damage to the display by playing a graphic intensive game as all the power and heat generated would be on your Mac. It is possible to overdrive a display, however, the Apple Cinema displays are protected against that. If it's a bad cable, you can always pick up a replacement on eBay to switch out with.

You might want to do some googling to see if anyone else has experience in repairing a 24" Cinema display. There's still a lot of older cinema displays around. Another thing to think about.... check on eBay to see if someone has a 24" Cinema display with a bad screen that they want to sell cheap. That's a good way to get parts and maybe swap out the logic board.

If I posted good pictures of the logic board and power supply unit, would you be able to visually identify if anything looks damaged? Or where the fuse is located?

Probably not since the logic boards for the MacBook Pro models are different. As far as spotting damage on the logic board, unless something is visibly shorted out or blackened from overheating, it would be like hunting for a needle in a haystack. Keep in mind what I suggested above about maybe getting hold of another 24" Cinema display that has a bad screen and swapping out the logic board. Just make sure you get it cheap enough to make the effort worthwhile.