Troubleshooting 24" Cinema Display problem

Hold a flashlight up to the screen while its connected to see if the image is still there. This is likely an issue with the backlight circuit.

Don't know if you've had any luck but just wanted to say that I recently had a similar problem with my 4 year old 24" Cinema Display. Shining a flash light into the dark screen revealed the issue was LED backlighting related.

I located an Apple Service manul online, took the unit apart and followed the diagnostics steps. In the end it pointed to the LCD panel itself being bad. Since a replacement panel costs around the same price as a new 27" Cinema Display, I opted to buy a new display.

Also, I should note that before the monitor blacked out, I'd noticed the display was dimmer than normal. This happened right after upgrading to Mavericks to I thought maybe it was driver related. I hooked the display up to my Macbook and it still had the same issue.

After a couple of weeks of being dim, the display finally went dark, never to return.

Good luck, hopefully yours is not fatal like mine was...

If you're handy, you can fix the display panel yourself. I purchased a 24" cinema display last week with no backlight and did some probing. I too found, using the test points, that the logic board's LED driver circuitry was still functional. This meant that the LED's themselves had burnt out. You may have actually noticed a burnt electronics smell just prior to the failure. I ended up stringing together 24 5mm white LEDs to replace the stock LED strip. This woked great, but only yeilded about 1/3rd the brightness of the highest setting. It was mainly a proof of concept project using only materials I had on hand. I have since purchased some high-output SMD LEDs to fabricate a new backlight strip with, which should bring the backlight output back into the stock range, if not higher. Ideally I would have been able to identify the package type of the LEDs used, but I had no luck.

JMR:

I too, find it disturbing that the panel only lasted 4 years. I was reluctant to purchase the 27" but decided to give Apple one more shot at this. I also picked up Apple Care so I guess if it's going to go, hopefully it happens within the 3 year coverage window. Hoping for the best...

Wish you the best of luck in getting yours fixed.

pshepard89:

Thanks for the info. As I still have my broken display, I may have to try this. I didn't look too closely at getting inside the panel itself once I determined it was bad. Since everything else appears ok, it would certainly be worth salvaging, if possible.

Can you provide a source as to where you purchased your LEDs? I'd greatly appreciate it as I have no problem digging further into the panel if it means being able to save it.

Thanks!

The 5mm LEDs that I used for the initial repair can be purchased from any electronics component supplier. Avoid Radio Shack at all costs. I wouldn't recommend using 5mm LED though. I've purchased some 5050 SMD LEDs for the next rendition. I will report back later in the week with my my results and possibly some photos. It's not somethign you want to attempt unless you're confident in your soldering skills. You'll also need to do a little math to figure out how to configure the LEDs and give them the right resistor.

Here are some photos of the 5mm LED job. I parralelled 3 strings of 8 LEDs wired in series and powered them directly from the 24v rail of the power supply. These LEDs are held in with hot glue. On the next repair, now that I know its worth while, I'll use the backlight driver from the logic board which will give me brightness control again. Pardon the mess, I had been working on wiring up that strip for a couple of hours. It really helps to have an adjustable lab power supply on the bench to test as you go. Also, note the hot spots in the bottom right and left corners of the screen. They are caused by misaligned LEDs.

Thanks for the info and photos! No problem with the soldering tasks. I look forward to your follow up.

Thanks again!

Thank you for all of the information! I also have a 24" cinema display with no backlight. The screen is producing an image though (confirmed by the flashlight test). Upon inspection of the logic board, all of the test points check out. However, a diode in one of the back light LED driver PWMs was clearly destroyed by overheating (completely charred). I replaced the diode with no luck. My next thought was to check the voltages at the STR connector where the display connects to the backlight driver. I am seeing 24v between STR0+, STR1+, STR2+ and ground, but 0v between the positive and negative pins for each respective string. It would seem that these voltages are incorrect, but I would just like to hear what some of you have to say before I spend $200 on a new logic board. While it is obvious that there was a defect in the logic board, I worry that the LED driver failure may have taken out the LEDs in the panel with it.

Thank you!

I haven't gotten any further with my repair. I recently purchased a string of LEDs but haven't had the time to attempt the replacement. I'm not to sure what to make of your voltage readings. Sorry.

Best of luck with your repairs!

Just have to chime in and say I have been running 2 of these monitors and the right one of the two has had flickering and more recently dimming more frequently. Right now it's completely black, but with the flashlight test it's still got images being displayed. It's gone fully black about four 4 times now, and each time I have fixed it by turning everything off at the wall and booting up again. Running a Mac Pro 2009 with PC GeForce 660 Ti Card and an active DVI to Display port adapter on this one, DP to mDP on the other display. Swapping ports yields the same result. So it's definitely the display.

TL:DR version..

Keen to see what results others have with retrofitting new LED.

Hi,

has anyone connected a new LED stripe and has still dimmable LEDs? Maybe theres someone how can give me the pin assignment in the connector?

Thanks

Hello everyone,

i have 2 Displays with the same Issue. The first one has the LEDs burnt out and the other one has just one led which lost its diffusor, so the LEDs dont stay on although they are working.

Im considering the fix proposed by pshepard89,

i would really love if you could tell us how you fixed the backlight driver issue.

If anyone is still trying to fix it pls contact me so we can help each other.

Thanks, Niksda