Ok so this is a pretty long story so I'll try and cut it down a bit.

So my parents bought this apple cinema display for work around 2010/2011 and it worked perfectly fine for a good few years until an issue started to appear where whenever you turned off the monitor or put it to sleep it wouldn't turn back on until you unplug and replug it multiple times and over time the amount of times you had to unplug and replug slowly increased to the point where its basically unusable. Anyway my parents gave it to me and its been sitting in my room collecting dust ever since. I've thought about taking it to the tip many times but its such a nice monitor and would be a shame to throw it out so I decided to try and fix it.

So after quite a bit of research I found that it wasn't just me having this issue, it seemed to be something a lot of people had issues with and as I dug deeper in to the forums my hope of repairing the monitor slowly diminished as I wasn't able to find a fix ANYWHERE. Some people fixed their monitors by buying a new power supply from apple for upwards of $100 which I wasn't prepared to do.

That was until I found this post: http://reismanitservices.blogspot.co.uk/2012/01/replacement-power-adapter-for-23-apple.html
It's a power supply fix for an older version of the monitor. That means I cant just use the same power supply they used so I was basically back to square one as I spent a good while looking for the schematics which I then found: http://tim.id.au/laptops/apple/displays/led_cinema_display_24.pdf
It had some useful information but not the power usage info so I looked for the monitors schematics instead which, again, I then found http://static1.1.sqspcdn.com/static/f/489821/16638029/1386278025880/LM240WU6-SDA1.pdf?token=ciLGt63EGO8JUyvEJ4d6lszxbGY=
And thats basically where I'm up to now as I've now reached the end of my electronics knowledge.

I don't need the speakers, webcam etc so if I could just power the monitor on its own with the logic board that will do but I just have no clue how to do it.

 

Wrote 23" in the title by mistake, its actually 24", sorry about that

 

There is a chance the problem is the power supply, which was moved inside the unit instead of being a separate brick. The MB diagram on p.16 in the service manual shows several voltage test points. If you're comfortable that you can do it safely, you could check #11-13. And you could unplug the power supply and check its output pins to confirm that it's the problem.

It's unlikely (but not impossible) that you could repair the power supply, but you could probably hack it like in the link you gave, to bring the power connections to the outside and then use a cheap(er) external power supply.

If you pull the power supply out, look it over carefully for any signs of damage. Pay special attention to any electrolytic capacitors. Look for domed tops or spewing out from their bottoms. The shotgun approach to repairing a power supply like this is to simply replace all the electrolytic capacitors. They're known to age and are a common cause of failure. So rather than spend time studying and diagnosing, just replace them all and hope for the best. Sometimes you get lucky. The bad news is that Apple probably didn't use and through-hole components. Doing board-level repair with surface mount parts is not a DIY for most of us.

 

There is a chance the problem is the power supply, which was moved inside the unit instead of being a separate brick. The MB diagram on p.16 in the service manual shows several voltage test points. If you're comfortable that you can do it safely, you could check #11-13. And you could unplug the power supply and check its output pins to confirm that it's the problem.

It's unlikely (but not impossible) that you could repair the power supply, but you could probably hack it like in the link you gave, to bring the power connections to the outside and then use a cheap(er) external power supply.

If you pull the power supply out, look it over carefully for any signs of damage. Pay special attention to any electrolytic capacitors. Look for domed tops or spewing out from their bottoms. The shotgun approach to repairing a power supply like this is to simply replace all the electrolytic capacitors. They're known to age and are a common cause of failure. So rather than spend time studying and diagnosing, just replace them all and hope for the best. Sometimes you get lucky. The bad news is that Apple probably didn't use and through-hole components. Doing board-level repair with surface mount parts is not a DIY for most of us.

I don't think I have the skills/tools necessary to fix the power supply which is why I was more lenient towards to 'hack' approach but I'd be willing to give it a try. That said, I removed the power supply from the case and found no damage to the capacitors and no visual damage to the board.. just a sooty like smell?. I'll send some pictures just in case they're of any use. If I'm not able to fix the power supply, like you mentioned, how would I go about bringing the power connections to the outside?

 

Did you measure any voltages? I mean, there's no guaranty that the PS is the problem. I'd say it's highly likely, but that's not the same as for sure.

See the words about the fuse on the board? If you can find the fuse, it's always worth checking.

The board shows the outputs it produces. I'm not sure how hard it might be to find an external supply with similar ratings.

 

Did you measure any voltages? I mean, there's no guaranty that the PS is the problem. I'd say it's highly likely, but that's not the same as for sure.

See the words about the fuse on the board? If you can find the fuse, it's always worth checking.

The board shows the outputs it produces. I'm not sure how hard it might be to find an external supply with similar ratings.

I have a multimeter for mains voltage but not for small components like this, I don't know if it would work given how small the points are.
I found the fuse, not really sure how I would go about checking it though and even if it were the fuse, that would mean that the monitor wouldn't work at all but in this case the monitor works after being reset multiple times. If you know what might cause that to happen maybe we could diagnose which component might cause the issues.

 

Bit of an update: I'm fairly certain that its the power supply, I wasn't able to get any readings out of it on the output pins and when I tested the logic board all was good.

I found an external power supply on ebay (I'm from the UK so its cool) - http://www.ebay.co.uk/itm/NEW-AC100...ower-Supply-/262407718071?hash=item3d18b804b7
I'm pretty sure they're the same specs but il post a screenshot of the specs on the old psu.

 

Tested the logic board? How did you manage to do that?

It seemed to me that the original power supply put out multiple voltages whereas that one on e-bay is 24V. Are you planning to use another regulator to get the other voltages? I admit I'm not sure on the details.

 

Tested the logic board? How did you manage to do that?

It seemed to me that the original power supply put out multiple voltages whereas that one on e-bay is 24V. Are you planning to use another regulator to get the other voltages? I admit I'm not sure on the details.

On the technician guide, on page 21, theres a page dedicated to sleep/wake issues and it goes through the steps to checking each part.

Thats actually a very good point about the power supply though... If I were to find out the voltage that the display needs on its own and unplug the speakers, webcam etc thats plugged in to the logic board, I could then find a power supply that fits just the needs of the display and nothing else?

 

Above my pay grade. I don't know how those various voltages are used, and whether the display might operate with just a single voltage.

If the power supply is not outputting something, how can you run diagnostics? Is the PS active for a while and then shuts down?

 

Above my pay grade. I don't know how those various voltages are used, and whether the display might operate with just a single voltage.

If the power supply is not outputting something, how can you run diagnostics? Is the PS active for a while and then shuts down?

It does work, I just have to turn it on and off quite a few times and then it suddenly springs to life. I have no idea why.

 

Oh crud, that makes it really tough to diagnose. Have you worked through the steps on p.18?

I'm curious if maybe your computer system log reports anything. DO you know how to go look at that with Console?

 

Oh crud, that makes it really tough to diagnose. Have you worked through the steps on p.18?

I'm curious if maybe your computer system log reports anything. DO you know how to go look at that with Console?

I wasn't able to get an image out of the display after hooking it all up so its either the power supply finally gave up or I somehow damaged the lcd panel.

 

One of the possibilities for the original problem is bad connections. Mucking around inside may have pushed it over the edge. It could be a clue. Of course Murphy's law dictates that it wasn't cured by the same disturbances.

 

One of the possibilities for the original problem is bad connections. Mucking around inside may have pushed it over the edge. It could be a clue. Of course Murphy's law dictates that it wasn't cured by the same disturbances.

Where do I go from here then? I'm starting to think this is more trouble than its worth

 

Yup, that has to be a consideration. You might get lucky poking around and you might not. It could be as simple as a wobbly connection or it could be a broken solder joint on the main processor on the motherboard. If your skill level was higher, you might have a chance but frankly it could be a pretty big challenge even for a skilled technician.

 

Yup, that has to be a consideration. You might get lucky poking around and you might not. It could be as simple as a wobbly connection or it could be a broken solder joint on the main processor on the motherboard. If your skill level was higher, you might have a chance but frankly it could be a pretty big challenge even for a skilled technician.

Ok, so I desoldered the fuse on the power supply to take a look and it is definitely blown. I have no idea whether that was the cause of the original problem or not but its something at least.

 

Ok, so I'm going to assume that the LCD display wasn't damaged. Trying to find a way to power everything individually (webcam,speakers etc) sounds like a pain so I'm going back to the original aim and just try to get the lcd display powered. However, for the life of me, I cant find its power requirements anywhere on this and I'm not sure what I'm even looking for to be honest.

There's another issue as well whereas in order to get power to the logic board I need to use the power connectors that the old power supply uses. In a simple world maybe I could use the old power supply as a complicated converter but I'm fairly sure that wont work.

Still work to be done but I'm still motivated to learn more and fix this monitor.

 

Did you see this quote in the Apple documentation?

"The unit has no buttons. Power is controlled by the state of the connected computer. It is
OFF if it detects the DisplayPort source is powered o . It is in Sleep if it detects the DisplayPort source is powered but does not send a video signal (i.e., Display Sleep). It is ON when the DisplayPort source sends a valid video signal. "​

Could it be that simple, maybe a dodgy cable? It'd be helpful to have a known good unit side by side. You'd be able to measure voltages and even swap parts to isolate the problem. I did that once with a laptop. Bought a duplicate of the one I was working on from Craigslist, and actually resold it at a profit when I was done with it. I highly recommend this strategy, if you can find one.

When it's plugged in but not "on", are the USB ports powered?

My larger point is, you still need a good diagnosis.

 

I know this is an older thread, but I had a similar issue with my 30" cinema display and just figured out the issue after multiple power bricks and about a year of off-and-on troubleshooting.
I researched many times about this issue and it seems it was pretty common. Although these monitors are a bit old nowadays, they are still great monitors. Most of the solutions that I read had to do with the power supply or brightness setting. There were also a couple that mentioned the monitor settings in preferences, and the infamous "taping of the ground connection" in the connection to the power brick itself. None of that helped for any length of time. My monitor was not waking up after being turned off at first. I set my computer to never sleep, which helped, but eventually my monitor would flicker and sometimes just turn on and off repeatedly and endlessly. So today I started testing the buttons on the side....and voila! It was the power and/or brightness buttons on the side of the monitor!!! They were contacting continuously for some reason. For the moment as a temp fix, I managed to get a sharp knife in the side of the casing where the power buttons are and pried it outward to create some space. Then I inserted a thin plastic clip to keep it in that state. The monitor has not malfunctioned since!!! I really hope this will help someone at some point, because I went through alot trying to figure this one out. Good luck!