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Backlight dead, no brightness controls, LCD hardware OK

Hello,

I have a strange problem on my Macbook Pro.

The backlight is not working.

Everything else is Ok, external Display works fine.

Also I have backlight on that LCD when I connect it to another macbook pro.

I checked the inverter, the I/O Board and wiring.

Found the I/O board faulty (smd resistance dead) and replaced it.

Still, the backlight is dead. (from the beginning when I turn on the MBP)

What I found strange is, that also there is no backlight-control-symbol showing on the sreen when I push F1, F2 (I made sure that it is not Fn-F1, F2). Rest of the F keys are working as they should.

Can that really be a hardware fault? - I would at least expect showing up the backlight symbol on the screen.

The display is properly recognised in the properties as it should (about my mac).

Does anybody have an idea what I am probably missing? Is there probably some analysis program that might give more information?

Thanks for your help.

Kind regards,

cal

Answer this question I have this problem too

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Do you mean the smd resistance on the logic board ? If so, do you get voltage at the smd resistance output after replacement cause the problem could be related to a faulty component located before the smd resistance ?

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Hi,

thank you for the tips.

I performed the PRAM Reset and also the Target mode booting.

It did not help. Also the OS was installed completely freshly just before.

I have no backlight from the beginning of the booting - so I do not think it is an OSX problem.

What might be the critical hint is, that my brightness controls are not accessible - means that if I push the F1 or F2 keys, even the icon on the screen is not showing up. This is very strange isn't it?

May be someone has an insight into the system structure and can conclude on the faulty part. My conclusion would have been, that the display is not recogized properly and so it gives no control for brightness (like for external displays) - but the display is properly shown in the "About my mac"....

Suggestions are welcome....

Cheers, cal

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@Lemerise: it was afaukty SMD resistor on the I/O Board - I replaced the whole board. But this did not bring the backlight back. May be someone could instruct me how to measure the input voltage (4 wires).

Thanks.

Cal

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5 Answers

Most Helpful Answer

I offer not a solution, but a means to check if the MacBook Pro is functioning despite a failed display.

Boot Single-User mode (command-S while powering on).

Let go at the chime or after a similar period if you have no chime (I have none).

The drive noise will stop.

Type:

shutdown -h now

Press Enter.

The MBP should shutdown.

This means it is functioning, at least to some degree. I thought my MBP was dead: booted with no indications of life. I don't have a means to target-boot it, but this single-user shutdown trick gave me hope.

-jasonc

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First, try resetting your NVRAM on your macbook pro. Turn the system off, hold down COMMAND+OPTION+P+R and turn it on with any remaining fingers you can spare (or a pencil held in your teeth). It will bong, then pause, then bong again. Release and your system's boot settings have been reset, but you will have lost no data.

If that doesn't resolve it, it's either software or hardware. One way to rule out software entirely is to boot the affected macbook off of a known working mac.

1. Hold down Alt/Option when booting the affected macbook, until you get the choices of devices to boot from.

2. Then boot a known working mac up in target mode. Hold down T (just T) while booting a known working mac.

3. Next, hook the two macs up with a firewire cable.

4. The known good mac's drive will now show up in the affected Macbook's boot menu. Choose that and boot. It will boot using the known good mac's hard drive entirely.

If the problem persists on the affected mac, you can rest assured that the issue lies in hardware, as you've just booted it with a fully separate, known working MacOS load.

If the problem does not persist, then it is a software issue, and you may want to attempt a repair install.

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chimi N154C6 only works with 2008 model of macbook pro 2.4-26

for some reason logic board does not see the back light in the 2007 model macbook pro 2.4 or 2.2 as i tried same thing and works good with other lcd

but when i test the n54c6 dark screen again hope this helps

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The solution to your problem is the screen cable!!!!

Just order 2-3 screen cables and try it.

This is ridiculous apple trick to make more money.

The hardware of any apple is perfect exert cables.

This 100% solution.

you change one cable and not work try different seller.

Regards JIMMY (apple Pro engineer)

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The cable is so thin inside and by closing the lid often brakes. YOU can't even solder it because is made less than 1mm thickness. And why? because the data will transfer quicker. Thats nano-tricks but what about have something like graphene with high mobility and 99% of breakdown..... So first you will think is software problem, later a screen problem, later a motherboard problem.... but that is how you make money!!!!!!!!!!!

CABLE BROTHER!!!

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Hi, i have the same problem:

i have broken the LED display on my macbook pro and after changed it, new brand new one shows the desktop but without brightness: i can see the display control panel and also regulate the brightness but even with maximum of it the light is not working.

The problem is that with the old display the lamp works but obviously i can't see anything 'cause the display is broken. any ideas for the solution?

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hey idelloro, did you ever figure yours out? I have the identical issue and mine also is experiencing the ever popular "wifi: no hardware installed. Anybody know what ties them all in together? tried everything, replacing leds replacing cables, tested the fuses and wled driver mentioned in the mac rumors forum. im really at a loss.

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hi Jay... idon't know what to say. i asked to a guy who worked for apple ad he said it's strange: the display replacement should fix the problem. as u say i tried to change cables and one time more the display but nothing works yet. what about your wifi? did u tried to change the wifi board (i don't know even if is possible)? good luck for your mac! if i will find a solution i will post it here. good luck! bye

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idelloro, i actually was able to get everything working separately if that makes sense? but i'll explain a little better. I had wound up rechecking the schematic, after i had last posted you, checked it for soldering the "fuse" from the wled driver and turns out i had been checking the wrong fuse the whole time. so i replaced that fuse which was referenced in another thread on macrumors i believe, then i messed around and messed around with the osx software from top to bottom and no changes were noticed and wifi hardware still not recognized, I have had so many of these in the past and not sure if prior to my last post, maybe put the wrong wifi card in it or what but i changed it with another wifi card that i had sitting here and rebooted, and reset the p-ram the option-command, p and r while powering up and everything worked perfectly.

here is the post that i had to go back and read through for checking the backlight fuse and replacing it for many different models of mbook pro's

http://forums.macrumors.com/showthread.p...

be careful because there are 41 + pages of posts on this one single thread and that kinda confused me a bit too.

but all is well and thanks for checking into that idelloro, and moving forward for Ben, maybe the macrumors post will help you that i have just left the link for. im definitely not the first one on ifixit even to reference this post so i know it's a big problem and a lot of people on macrumors have reported successful results in this thread as well.

thanks to all

jay

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