Apple order number MC007LL/A / 27" 2560x1440 pixel display

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What components need replacing on the Logic board?

Black... No Display but power/sound/etc. is fine

All blogs read Replace one of the following:

•Power Supply

• Logic Board

• LCD Panel

Since Im getting power Ive ruled out the power supply.

Next, on to the Logic board.

What needs to be checked? Capacitors?

Please confirm the most likey suspects.

Thanks

Answered! View the answer I have this problem too

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Hi All... just wanted to post that i have had many issues with the backlight failing on my Apple LED Cinema Display 27". While Michael and others on this post have commendable electronics skills, on my display, I have localized the problem to be with the All-In-One Cable. Swapping out power supply and logic boards did nothing to solve my intermittent problem of the backlight going out. But swapping out the cable solved it for me... for a time. My display is 5-years old and I am currently on my fourth All-In-One cable (922-9362). It's a poor design. The cable seems to last for about 12-18 months and then starts going out intermittently without any major event happening. Why someone would combine a USB, Power, and Mini-Display into a single cable is beyond me... except that they can charge $140. for it! Cables are typically reliable and usually be able to be taken for granted. Unfortunately, in this case, I have found it to be anything but. Paras.

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18 Answers

Chosen Solution

Jason, this is not as easy as just recommending a certain part that has failed. You do want to check your logic board over and see if you find any bulging or leaking capacitors. Just because the power /sound/etc. may be there, you can also not rule out the power supply. It may not supply the power to the LED backlight. You will need to check on that as well, take a good luck on the logic board. There should also be a fuse for the backlight, which may have failed. Post a couple of hi-res images of your logic board with your question, so we may look at it and see if we can come up with something more concrete. I would also suggest that you try the Apple Deep Dive for Blank / No Video, No Backlight:

Check Result Action Code

1. Connect display to AC power source. Connect Mini DisplayPort, MagSafe and USB

connectors into a known good, supported, powered-up portable. Verify display’s USB

hub and built-in camera are listed in the System Profiler’s USB device tree.

Yes

Power is available to the display logic board, and USB communication working.

Go to step 2.

No

Go to Dead Unit/No Power.

2. Unplug and replug Mini DisplayPort connector into a known-good, supported, powered-up portable system and monitor the portable’s display. Verify that the

portable’s display briefly turns off then back on.

Yes

LCD is powered and detected by system. Go to step 7.

No

Suspected no power to LCD panel or no DisplayPort connection with system. Go

to step 3.

3. Remove glass and LCD panel screws, slightly pivot LCD panel and verify that the internal DisplayPort cable (part of all-inone cable) and function cable are fully connected to LCD panel and logic board.

Yes

Go to step 4.

No

Reseat DisplayPort connection to LCD panel and/or function cable connections between logic board and LCD panel and retest.

If issue persists go to step 4.

For any damaged cable, replace affected cable before testing again:

- all-in-one cable.

- function cable.

4. Unplug and replug Mini DisplayPort connector into a known-good, supported,

powered-up portable system and monitor the portable’s display. Verify that the

portable’s display briefly turns off then back on.

Yes

LCD is powered and detected by system. Go to step 7.

No

Suspect no power to LCD. Replace function cable and retest. If issue persists go to

step 5.

5. Replace all-in-one cable and reinstall LCD. Unplug and replug the Mini DisplayPort

connector into a knowngood, supported, powered-up portable system and monitor

the portable’s display. Verify that the portable’s display briefly turns off then back on.

Yes

LCD panel powered and detected by system. Go to step 7.

No

LCD panel still not detected by system. Suspect no LCD power from logic board.

Go to step 6.

6. Replace logic board and reinstall LCD. Unplug and replug the Mini DisplayPort

connector into a knowngood, supported, powered-up portable system and monitor

the portable’s display. Verify that the portable’s display briefly turns off then back on.

Yes

LCD panel powered and detected by system. Go to step 7.

No

LCD panel still not detected by system with replaced function cable, all-in-one cable and logic board. Suspect LCD panel video input damage.

Replace LCD panel.

7. If the Blank/No Video/No Backlight issue persists, darken room and connect to a knowngood supported system. Verify backlight is present by looking for faint glow from display.

Yes

LCD panel powered, detected by system and backlight is ON but there is no video on LCD. Replace LCD panel.

No

LCD panel is detected by system but no backlight. Check whether video is present on LCD. Go to step 8.

8. Shine bright (low heat) flashlight into the front of the LCD. and verify if any image is

being displayed.

Yes

Video is present, so issue is only with missing backlight. Go to step 9.

No

No image displayed on LCD Replace LCD panel.

9. Remove glass and LCD panel screws, lift LCD panel to verify that the function cable, and LED backlight driver cable connections are secure. See Functional Overview.

Yes

If connections are OK and secure and there is still no backlight, go to step 10.

No

If any cable is damaged, replace affected cable and retest:

- function cable

- LED backlight driver cable (part of LCD panel)

10. Remove LCD panel. Set digital multimeter to DC and correct range, and verify that a 23.3–25.7 V DC voltage is present between logic board test point (24 V DC) and chassis ground (GND).

Yes

24 V DC power for backlight is present on logic board, but no backlight. Suspect no

V-sync signal coming to logic board. Go to step 11.

No

No 24 V DC present for LED backlight power. Replace power supply.

11. Replace function cable and retest. Verify that the no backlight issue is fixed.

Yes

Defective function cable prevented backlight from being enabled by logic board.

No

Go to step 12.

12. Verify if the LED backlight driver cable (part of the LCD panel) has any signs of pinched or shorted wires. Also remove the logic board and verify if one or more of the three square inductors or adjacent components on top of board show signs of overheating.

Yes

LED backlight driver cable on LCD panel found damaged. Replace LCD panel, (make

sure that you don’t pinch the LED driver cable from LCD panel) and retest. If the no backlight issue persists after LCD panel replacement, replace logic board (LED backlight output from logic board had been damaged by shorted cable.)

No

Suspect no LED backlight output from logic board: go to step 12.

13. Replace logic board and verify that the no backlight issue is fixed.

Yes

Defective logic board LED backlight driver output.

No

Replace LCD panel.

Before you go and replace anything let us know what you found. Hope this helps, good luck.

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I replaced my power supply after seeing the screen on but no black light. Its not working still, Now i am returning the power supply i bought and going to buy the logic board if that doesn’t work I will throw this monitor in the trash.

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@Tyler Brown, by just replacing the PSU you will not fix the backlight components. Do you have any board level experience, the tools to do some board level repair?

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I have very limited experience with a soldering gun but youtube has some good videos for learning. What do i have to look for. I can purchase any tools i will need btw.

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Okay start of by telling us the serial number to your computer. With that we can get the description of the hardware. Your PSU was ruled out since you have a new one. Tell us exactly what your computer does (or does not ) do. Also, let us know what you have done so far.

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Ok about to start the project again. The computer I hook it up to is a MacBook Pro mid 2012. The monitor will flash sometimes from the initial plug in then stay black. I know it's knot the PSU because I replaced it like I said above. I am now going to try replacing the logic board. Btw when I shine a flash light I can see that the LCD is displaying my computer screen just no black light.

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introduction

Before you choose this solution, keep in mind, there are many problems that cause no backlight. For example the mosfet, coil and diode components may be broken. In this case the driver detects a failure (with the feedback resistor) and turns off. In my case everything was right. The microcontroller doesn't provide the PWM signal. But it took a long time to get this information. First I measured the signals on the board. Is the driver enabled? What is the input value of the PWM (S1 and S2) pin. I also checked (with the help of the data sheet) the mosfets, coils and diodes: Which pin of the driver is connected to the gate of what mosfet and what kind of function does it have? In the end I found out, that the external components are ok, so I began to make some tests with the driver!

In the image

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100% pwm signal

you can see the little wire that put the 3.3 voltage as input for the pwm signal. The backlight turns on and the cinema display is alive again!

the long story

After four years of using the backlight of the LED Cinema Display 27" was turned off. First the backlight was very low or was flickering while trying to dim the display via the system panel. I turned the display off and on and then it was dark.

With the help of a torch light I saw a faint image of the desktop. USB and magsafe were working as well. So the display is working without the backlight.

First of all I teardowned the display like it shown in Teardown Apple Display

The interesting parts are

  • the led driver HV9982
  • the mosfets and coils of the driver (producing 80 voltage for the led stripes)
  • the microcontroller

The led driver (called HV9982) is responsible to drive the leds stripes with current. It cares about the right current, because LEDs require more precise current management. The data sheet of the HV9982 you can find some basic information about the driver and this function:

HV9982 is a three-channel, closed loop, peak-current mode PWM controller designed to drive a constant out- put current. It can be used for driving either RGB LEDs or multiple channels of white LEDs.

identifying the components

In the next image you can see the led driver with its external components:

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the led driver

  • the mosfet, coils and feedback resistors (orange)
  • the connector for the led stripes (green)
  • the led driver chip (blue)

Using the datasheet of the led driver we get some interesting facts about the pins:

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the pins of the led driver

The led driver is controlled by the microntroller in the next picture:

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the microcontoller

The controller turns the led driver on if the computer is connected via thunderbolt cable. With a multimeter you can measure a 3.3 volt signal on pin 10 (enabled). If the computer is unplugged then the signal is bound to ground. But be aware the is only litte space between the pins! Keep an eye on it to avoid short circuits! (To be honest, I did three short circuits, one hurts a bit and one does a nice spark.)

identifying the connections

With the multimeter you can track the connections from pin to pin. I found out that the microntroller is connected to the pin 10 (enabled) and the pwm pins (17,18,19). The S1 and S2 pin are bound to ground and that means that the led driver is driven in the PWM mode. With the help of an oscilloscope I found out that the microcontroller does not send a PWM signal. He turns the led driver on but "forget" the create the PWM signal. In this case the backlight stays dark without any light. And you think the display is broken. (see for PWM)

But we have some luck! We can bridge the signal to 100%. We just connect the PWM pins to logical one and that is 3.3 volt. I found a pad that give me the 3.3 voltage and the pwm pins from the microcontoller are bridget by three 0 ohm resistor (labeled with R1132, R1133 and R1135). You cannot just put 3.3 volt to the pwm pins because they are connected with the microcontroller. This would cause a short circuit. In the following image you can see how the microntroller is connected to the pwm pins of the led driver:

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the connection the the pwm pins

The "R1" is a pull down resistor which is used the put a logical 0 to the pwm pins if the microncontroller does nothing. Now we make the following connection:

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the modified schema with constant 100% PWM

The led driver is a three channel pwm controller and the board contains all components for three channels and the connector is prepared for three channel but channel three is not used! So don't put 3.3 ohn R1133! In this case the led driver detects an error and switch off. The led cinema display has only two led stripes! Therefore connect only R1135 and R1132 with 3.3 volt.

So what do you think now? The problem is not a hardware problem, it is a software problem. The software within the microcontroller won't create the pwm signal. Unfortunately we don't have the source code, so we are not able to patch the firmware. We just cut the connections from the microcontroller and send now a pwm signal about 100%. You aren't able to dim any more and you needn't buy a new one! Is this a software error or just a hint that you should buy a new display?

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the 3.3 volt pad and the 0 ohm resistors

Good luck! Please keep in mind:

  • Avoid short circuit! The spaces between the components are very small!
  • The led driver creates up to 80 voltage!! That hurt's!
  • The board has 24 voltage!
  • You need two solder irons to unsolder the resistors.

next steps

  • Disassamble the firmware and find the interesting code
  • Maybe we find a code that is used to disable pwm after reaching a curtain value?
  • Maybe we find a code that simulates flickering and abnormal dimming to give the user some impression that the cinema display is "going" to get out of order next time?
  • Or it is just an error and the firmware thinks, that the display is in sleeping mode.

PS: It was the **third display** where the backlight turns out. Unfortunately I didn't check them and they are trashed, because the local apple dealer said, that repairing is too expensive than buying a new one!

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full backlight again

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Well done !!!!! , you did all that without a boardview and schematic? Are you positive the driver is not a QFN?

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Having repaired several hundred of these units and advising as to source, I would say that the implication that a software bug or intentionally timed failure is ludicrous. The processor does vary the signal but as a protective measure as I have described numerous times before. The case of an momentary flicker and viewable unlit panel operation is not solved by a replacement board because the problem is not on the logic board. A new logic board is relatively inexpensive and the monitors were worth it to a point recently but wouldn't help this problem. The same can not be said for the power supply. So much misinformation on these monitors that real information gets buried. A fix for the power supply under load problem would be your "next" step. Of course, repairing the board you have now altered will be an interesting challenge of your soldering skills.

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Hi John,

yes, I do it without any schematic. Just checked some connections with a multimeter and the data sheet of the driver. The driver is a QFN chip but you can touch the solder pads and that is some what thrilling because you can very easily connect to pins. For example: the enabled pin is next to VDD and VIN.

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Hi Hedrickja,

there are some firmware updates for the cinema display (https://support.apple.com/de_DE/download...). So a software bug is not so ludicrous, I think. Maybe they learnt from Volkswagen. I don't know, but the led cinema display is working again now. If I ask the local apple dealer for new logic board it took always 800 €! So my company decided to buy a new display. We got three cinema display and the backlight of all them turned off after the extended warranty time.

<quote>

The processor does vary the signal but as a protective measure as I have described numerous times before

<quote>

That is interesting, but where did you described this?

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I don't know what 800 ? is but new ones are avail. for $120 US in factory packaging. I paid about $99 retail for the last one I bought. It would not help you anyway. Also, with the monitors that are available now, repairs are becoming non-economical. Yes, there are always firmware revisions along the dev path but not ones that effect a failure years later. If Apple were to plan a failure like that and some disgruntled employee or reverse engineering tech were to discover or disclose it, it would be financial and marketing SUICIDE. The Volk debacle was a decision to try to salvage a serious dev problem instead of getting fired for failing to bring to market, not build their cars to fail miserably right after the warranty period. There were a small group of people desperate from their failure to solve a design problem. Placing a kill code in the monitor is much more devious and Apple consumers would recognize that. Risking their entire company just to sell a few more monitors. I think not.

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Update (28.02.2016)

my Cinema Display 24" FIX :)

-------------------

Step 1: Remove the 3 resistors R0444,R0459,R0445

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-------------------

Step 2: connect the 3 pull-down resistors to 3.3V (

ONLY the page to the driver IC)

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-------------------

END FIX

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-------------------

Have fun and viel Spaß ^^

-->!!WARNUNG /Warning !!<--

the L-board has 24& 70 voltage

**Nachbau auf eigene Gefahr,ich übernehme keine Haftung**

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Hi Willi! This looks great!

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thanks to their idea with the PWM Bypass ^^

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Dear Willi, thanks for your work n the 24 inch display.

Not speaking german, i would greatly enjoy if you detail a bit your steps.

First you remove the three resistors

Then you bring 3.3v to where?

Thanks by advance.

Dav

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Fix done today. works like a charm.

danke Willi

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danke danke danke :)

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I had the same problems. Backlight was gone or very low.

The short story: I found out that the micro controller does not send the PWM signal to the LED driver.

Very mysterious! I checked the LED driver components (Mosfett, diode), I read the data sheet to understand the function of the HV9982 (LED driver). In the end there was no hardware problem there. If I connected the computer the micro controller enabled the LED driver but "forget" so send the PWM signal, so the LEDs stayed off.

Mmmm...maybe this is a software error or Apple wants to tell me to buy a new one? So I bridged the PWM input pins with a little wire connected to a 3.3 V pad (which I found about 1 cm around). Nice that die PWM output pins of the micro controller were bridged by 0 ohm resistors, so I could remove same and cut the connection from the micro controller. And then I got full backlight again. Of course I am not able to dim the backlight anymore.

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My Apple LED Cinema Display 27" is still up and running.

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Hello Michael! Do you know anything about the thunderbolt display? Mine has the same symptoms, but the board is different. I was able to locate the indicated pins, but I did not find any 3.3v pad. Sorry for my english, I'm brazilian and I'm using google translate hoho

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These are repairable, they use the same lg panel found in the 2011 27 inch Imac.

This repair is not for the average repair person.

As any apple repair person knows, (official or not!) the 2011 Imac had serious backlight issues.

Repair Information is sparse and difficult to find, not to mention the many (So bloody many!) people who refuse to believe you.

The repair is simple:

Thunderbolt display or Imac 2011 27 inch.

Check all functions before hand, rule out backlight driver, psu, cables etc.

Take out lcd panel, disassemble lcd panel, only as far as you need to to get at the backlight strip.

remove backlight strip, resolder 4 or 5 pin plug on backlight strip even if it looks clean.

This is a factory defect.

I am a computer technician in Australia who has to do these and other repairs that apple won't admit are issues fairly often.

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Hi John, good to know you are in Australia. Where are you located?

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state of Victoria.

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That's awesome. Would you be able to contact me as I have one without backlight, well, sometimes it still lights up and later goes blank. I wonder if I can fine someone for help. Cheers

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I have an LED cinema display 24" from 2009, I have excatly the problem that the screen blanks out after a 1 sec flash of the image (prob. LED driver signal turns down). I was about to try the bypass solution above for the 3.3V drive input, but then wanted to ask first if the same backlight strip probem problem could be on my LED Display as well, because I would not want to loose the dispay dimming possibility. THanks in advance, robertnawfal@hotmail.com

I Did disassemble my display down to the Background lights, but I did not do any soldering yet.

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Hey Robert Nawfal, where are you located currently?

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With all due respect for the great investigative work done by Michael (and Willi) I have to admit that John the Aussie tech was right on the money with his answer.

It appears the Thunderbolt Cinema 27" is affected by the same plague as the 27" Imac (2011), which is....(drum roll)...the LG display.

Despite the fact that the iMac has CCFL backlight and the Cinema Thunderbolt 27 has LED bklt, the fault is exactly the same and in the same place: backlight connectors on LCD panel.

Long story short: just finished spending 2 days on fixing the Cinema 27.

1- octopus cable damaged ------> replaced with new. Backlight still had a mind of its own (working whenever it felt like it) and eventually it stopped working altogether.

2- tried Michael's mod -----> backlight wouldn't still kick in at all, but the image on the lcd flickered

3- undone Michael's mod

4- remembered the iMac LG failure and took Aussie John's advice. Decided to bite the bullet and took the LCD panel apart.

5- re-soldered both backlight connectors on the LED strip

6- the Cinema Thunderbolt is back to life !!!!

The job is extremely difficult (not for the faint of heart) and requires excellent skills (disassembly and soldering).

Good luck everyone and thanks again to : John, Michael and Willi !!!

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Hi io nut, would it be possible to post some photos of the spot that you re-soldered? I recon mine is also due to the connector issue. Thank you.

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I would like to try this as well, some photos would be helpful.

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Fua and Robert, I did not have the luxury of time to take pictures nor I had the intention of doing a write up on the repair.

The most delicate job is to get to the connectors which are located in the bottom corners of the lcd panel. Follow the backlight molex ribbon cable taped to the metal shield of the lcd panel. At some point the molex splits in two, one leading to the right bottom corner and the other to the left. You can see the connectors if you peel the aluminium tape that covers them. This is just to locate the connectors. To re-solder the connectors you will have to gain access from the flip side of the screen, under the lcd panel and the optical sheets- this is the most challenging part.

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@John &Io Nut

I have an LED cinema display 24" from 2009, I have excatly the problem that the screen blanks out after a 1 sec flash of the image (probably LED driver signal turns down). I was about to try the bypass solution above for the 3.3V drive input, but then wanted to ask first if the same backlight strip probem problem could be on my LED Display as well, because I would not want to loose the dispay dimming possibility.

update:

So I did take the LG LCD panel apart in search for the notorius LED Strip, see pictures:

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Taking the LCD apart:

The LCD frame,

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The Backlight panel,

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The plastic frame,

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The glass of the panel,

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The back plate,

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Finally getting down to the LED Strip

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So I did resolder the LED connector (just added some solder to it and re-heated the 5 pins again thoroughly), but my problem still persists, the LED stripe only flashes quick at connection display port connection time. I am considering of doing some logic measurements tonight with my oscilloscope for the LED driver, but the willi fix for bypassing the 3.3V is starting to sound tempting (still trying to find out the real reason for this failure, and I have to admit that the LED stripe fault sounds more plausible to me due to the drive signal LED shutdown after one second flash.

Update (23.02.2017)

@io nut

I made some advancements with the display but the reason for the fault is still unclear.

All of a sudden the LEDs decided to turn on again.

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I am convinced that it has something to do with the horizontal positioning of my setup. While lit I quickly checked the LEDs and realised that Led nr. 27,30,40 and 60 are out. Next day when I started the display the background lighting did not lit again.

I figured it might have something to do with grounding and tried out connecting the displayport without the USB cable. No effect the LEDs turn on with or without the other USB connector and/or the Powerconnector. I realised that the LED cinema display brightness can not be adjusted without the USB cable connected to the my macbook pro.

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Update (26.02.2017)

LED illumination pattern 2/3 Leds.

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LED illumination pattern every third LED

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Update (27.02.2017)

So after all the MODs my display is running again. Eventually I ended up only changing 9 capacitors (3 pcs of each of the black ones in the pic, the orange ones I still have originals) on the powersupply,

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and resoldering the LED stripe connector,

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in addition I assembled and reassembled the display several times (loose connectors).

So Im still not convinced about the source of the fault and Im now testing the display for a week, lets see if it actually stays on.

Update (05.03.2017)

My Apple LED Cinema Display 24" is still up and running.

Update (03/22/2017)

Unfortunately I have to report that my LED cinema display died again after one month of fluent usage. So Im back to square zero. :!

Update (15.05.2017)

I decided to try out if my display runs and it seems to run again :). So lets see for how long, but I am suspecting some sort of capacitor voltages that are incorrect due to capacitor ageing.

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Robert, excellent pictures !

If you are absolutely sure you have resoldered properly the connector, and the symptoms are the same that means the problem must originate somewhere else. Your symptoms are different from the ones I have experienced, but it definitely sounds like a detected fault triggers the backlight to shut down. (is it just the backlight that shuts off?- do you have an image on lcd if you shine a light on the lcd?)

Does the whole strip light up during that 1 second? Noticed any LED stay unlit?

Is the octopus cable ok? Tried different one? (Yours could short out, like mine did initially).

Cover all your bases and now that you got so far, do not rush ! Ultimately, try the bypass mod, but in a non-destructive way, so you can undo it if necessary.

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Thanks for the rapid answer. I basically ruled out the octopus cable malfunctioning because I actually managed to start the monitor, but only the first time. So I got a nice and bright (with backlight) picture, but as soon as I restart the monitor the backlight just blinks and then shuts down again, probably some capacitor malfunctioning in the Logic board.

I did not realise any dark LEDs during the very brief flash of the LEDs (cant say for sure though). So I basically now have the monitor open and plain LEDs connected to the Logic board.

I ll try to get another octopus cable somewhere to try out, I havent tried that yet. Though I think the cable is not the fault since I have succesfully turned on the monitor 3 times (always after a long break or disassembly to let the charges out).

How would you do the bypass in a non destructive way? I mean once I have the resistors out it could be quite a challenge to get them back into their places.

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Non destructive way, meaning do not cut traces or destroy the 0 ohm resistors when you take them out. Use two fine tip irons ( or one tweezer tip preferably) and heat up both ends of the resistor at the same time and lift it off the board. Save it on a sticky tape in case you need to put it back on. Solder it back the same way, but use some flux on the pads. It is easy.

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I am assuming, you have done the firmware update for both the monitor and the macbook...?!

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I am actually running an old macbook pro mid2010 15" OSX 10.9.5 so it still has a display port instead of thunderbolt port, the firmware update I found would not install saying "your computer does not need this update " propably due to the fact that I have a display port instead of the never thunderbolt port.

I also tried the Macbook pro of my girlfriend, mid2010 13" running a OSX 10.11.6 El Capitan.

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  1. here are some pictures of the Cinema Display

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  1. Here's the back of the logic board

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Same problems here with an Apple Cinema Display 24 inch. The problem of flickering and no backlight occurs mostly when the ACD is connected again to my Macbook 5.1

I developed a 'workaround' that's still working after 6 months. (I suppose the problem has to do with ageing capacitors, a phenomenon I recognize from audio electronics).

The workaround is: discharge electric residue from all contacts of the display port plug of the ACD.

First disconnect the ACD from mains, and disconnect the all-in-one cable from your Mac.

Use a copper brush (like this one: http://www.tools.vocor.nl/data/articles/... ) and place it carefully on the displayport plug while connecting ground (chassis) with all contacts.

Then plugin the all-in-one cable to the Mac and after that attach the mains of the ACD (use a grounded connection).

Sometimes I renewed the NVRAM and the SMC of the Macbook, before attaching the ACD again.

Once in a while the backlight disappears for 0,5 seconds. An interruption that occurs less when you lower brightness.

(Changing the logic board, like Roy Kenjataimu descibed in his comment, mostly implies also discharging electric residues.)

I think an electric scheme is needed to search for an aged capacitor that might disrupt the proper working of the micro controller (as I suppose).

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I just want to thank everyone in this post, especially Mike and Willi for all the knowledge and effort. Here's mine and Willi's fix worked perfectly.

Mine is a 24 inch Apple Cinema Display. It was completely dark, although the fan was spinning, Megasafe was charging, USB worked, and the MacBook Pro's monitor briefly turned on and off while the Apple Cinema display flickered very briefly. I followed the service manual and found that very very dimmed image can be seen on the Apple Cinema when shining a flash light to it, this is a confirmation that the back light wasn't functioning properly. After getting a reading of 24v when testing TP81 in relation to the chassis ground, I decided to go with Willi's fix and gave it a shot (note that I'm not an electrician nor electrical engineer). And it worked, although the soldering was very difficult for me. As Willi said, remove R0444, 0445, and 0459, connect the three pull down resistors to the 3.3v (L0631?).

And here's a link to the service manual if anyone is interested:

https://www.manualslib.com/manual/685572...

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Hi

thank you for this great tutorial, I have done exactly as you've shown and I still have no black light and in fact the I can see the display when I use a touch but now it is flickering with no back light. Whilst before I could see an image but the display was not flickering. Can you please help me as it is urgent

thank you

Sam

Update (21.12.2015)

Please see attached photo

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Update (21.12.2015)

can you see the photo

Update (21.12.2015)

Hi the led driver you are referring to is it the small board that is attached to the LG screen where the function cable, heat sensor etc is connected to?

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Hi Sam

you have to check some points, the Mosfet-Gates, the Mosfet-Source and Pin 10 (enabled) of the led driver. Maybe make a photo from your board. For this you need an oscilloscope!

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Keep in mind, that R1133 is not used! If you put 3.3 volt on R1133 the led driver switches off.

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thank you for coming back to me I will do so now, give me few mins to send you a picture

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Can you check the voltage of the wire? It should have 3.3 volt.

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I have just put my meter on both ends of the red wire and I have zero no voltage

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check the all-in-one cable.... they are notorious on these!

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Follow up: I gave up trying to repair the logic board and ordered a new one. Cost almost 200$ (logic board + shipping + customs) because I live in europe. But it was worth it, the backlight is working fine and the monitor is usable once again. Hadn't used it in almost a year, already forgot what an amazing display it actually has.

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After reading posts from Willi and others on how to repair the 24" LED Cinema Display, I am happy to report that my monitor is working again. I found someone on Kijiji to perform the soldering for a reasonable price. As noted by others, you cannot change the brightness level and in my case it was too bright for my eyes after more than 15 minutes of looking at the screen. I'm using a Neutral Density Gel Filter sheet (made by Lee Filters for $10) over the screen to reduce the brightness. Hope this may help others that experienced the same problem with brightness.

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I don't mean any offense to anybody but this is one mess of a thread. Here's some IMO about this situation. The monitors are not worth repairing. 1) All of my customers from CAD operators to graphic designers are happier with a $150 32"1080P HDMI TV monitor. No, the video quality is not as good under a direct comparison but the size makes up for it and there is no eye strain. The adapter for MacBooks is a small additional cost. 2) The direct wiring of the LED circuit is not an acceptable solution to deal with the power supply problem because it stays on and you can't control the brightness, not a solution I could use with any client. 3) The backlighting strip connectors and the jumper connector are a fix I have tried a number of times. It works occasionally but isn't worth the time because the monitors suffer from intelligent cable problems and other issues such that when I fix one, the customer ends up bringing it back, 4) The claimed BIOS calendar timed destruction is something that simply doesn't exist because many of these monitors that see little usage are still working like they did since new. Unfortunately, by the time someone that comes here has had the frustrating experience of trying some of the carefully detailed solutions to no avail,,they will have wasted more time than these old monitors are worth. Unfortunately they simply do not hold up as well as MacBooks.

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Thats fine, you can go to cry somewhere else. If i have a monitor that cost me a lot of money and can be repaired by myself cheaply, Id like to know. I understanf that you prefer people not to know so you can repair more monitors, but thats no the spirit of this forum

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Have already forgotten about my 2009 ACD 24", it was standing around and getting dusty for 3 years now since it gets dark screen - thought thats it, no more spendign money, no time and no idea how to fix it ... In the last days I decide to give it a try after reading all yours comments and promising results. thanks for that!

When I bridged the resistors together R0821, R0804, R0896 and 3.3V it starts flashing like some described before... So I remembered this fault behaviour is shown by LED elsewhere when flashing is caused by overheating. While I disassemble the LG LCD unit, I was astonished about some sort of soot on the screen inside, maybe because of the mirror foil was getting crusty, baked all around the thin aluminium rail with LED on it...

Finally I decided to connect the 3.3V to the resistors separately. R0821 and R0804 are still flashing, but it works well for R0896! In conclusion only one of the 3x20 strings on the LED-rail will work, thats not that bright but sufficient and great for night shift.

Has anyone thought about replacing for a 12V-strip (60-LED-3528) ? Similar to someone's mod for older ACDs with CCFL-lamps I found on the internet

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Same result.

4 cinema display in my office: 1 OK with this FIX, 3 have flickering.

I'll try to connect 3.3V to single resistor soon...

I don't see solutions with this display.

Note: I buy new driver CHIP: i want to try to change this piece... but now I suppose the problem is led string..

BUT.. I can to try to SWAP good display (from the unit that working OK) to defect unit (with flickering) to check display... I'll try this ASAP

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@rokost: I try to connect 100% good display (perfect working on the repaired display) to other units with flickering (and fix).

Result: the flickering persist!!

So I suppose that the LED board is OK but driver CHIP is damaged..

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Maybe you are right about the faulty driver unit... Back then I had some different mysterious backlight dying issues on my 2008 MacBook Aluminium. First the keyboard light stopped working, later than display backlight too, but not at the same time. It was still usable for a desktop only, but I decided to replace the logicboard and it runs again perfectly.

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Hello everyone! Anyone know anything about the Thunderbolt Display? I have the same problems, but the logic board is different from ACD 24 "and 27".

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I realised that the display still sometimes just makes a flash and goes black again, but if I detach and reattach the power plug and move the mouse at the same time it functions always.

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Jason will be eternally grateful.
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