keyboard backlight repair

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Level 1

0 points

keyboard backlight repair

I took my Macbook Pro pretty much apart down to the keyboard and got it back together with no leftover parts. The only thing that does not work is the keyboard backlight. I do not see any connectors that I left off and would prefer to not take the motherboard out to see if I missed one unless I need to. Does anyone know where the backlight cable is connected or of anything else I might have done to kill it? Is it an especially delicate cable that I might have broken?

Macbook Pro, Mac OS X (10.6.4)

Posted on Oct 26, 2010 12:52 AM

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Answer 1

S.U.

Level 6

9,601 points

Oct 26, 2010 3:13 PM in response to penguinn

Welcome to Apple Discussions!

Before taking anything apart, you might try resetting the SMC or LabTic:

http://support.apple.com/kb/HT1411?viewlocale=en_US

http://www.apple.com/downloads/macosx/systemdiskutilities/labtick.html

If no joy, then it's time to try taking apart your Mac and see if you can spot the cable and see if it is broken or not well seated.

Good luck!

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Answer 2

penguinn Author

Level 1

0 points

Oct 26, 2010 6:17 PM in response to S.U.

Thanks for the suggestion but it seems to be a hardware problem. First, I took the Mac apart because of a little drinky spill that would not be covered by the extended warrantee. This is the aluminum model and replacing the keyboard is not an option, the whole top needs to be replaced at $250. I would do it if I knew that would fix the problem. The LED backlight string is probably controlled by an LED driver circuit and this may have overshot and killed the LEDs. I measure 4.95 volts at the connector for the light string no matter what the brightness setting is. Not having information as to how the driver works (is probably current sensing) I have no way to know if the driver (part of the m-board) is fried or not. So, I want to diagnose the LED string but I want to do the least disassembly possible until I know that I can fix it and put it back together. I don't know how many times the various fine pitch connectors on the m-board can be connected/disconnected without failing.

What I really need is some detailed information. Just a photo of the LED assembly (it is stuck to the black plastic that covers the keyboard) would help a lot. I need to know if it is just a series string of LEDs that connect only at the connector that is near the left side fan. If I can determine that it is failed I can get some new chip LEDs and or fix a bad solder joint or cracked circuit trace. Apple does not sell the little stick on LED string but makes you buy the whole top cover.

Does anyone have a late model Macbook Pro (the kind with the keys fitting in individual holes in the top cover, not the one with the easily removable keyboard) with the motherboard removed that they can photograph? I can certainly take it all apart again but that will mean three disassembly/assembly cycles before I get it working and I am afraid of the possibility of screwing up one of the many fine pitch connectors.

Also, if anyone has a schematic or description of how the LED driver works that would help me determine if it is working or not. My guess is that the driver overshot because of a temporary short and that it killed the LEDs.

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Answer 3

RDucci

Level 1

8 points

Nov 28, 2010 3:51 AM in response to penguinn

Hi Penguinn,
I have the same issue after having installed an MCE Optibay adapter removing the Superdrive and the factory HD and inserting a 1T SATA drive + a 128 GB boot SSD. i was following the instructions with absolute care...
Now , for some strange reasons, my backlight is dead: by pressing the keys f5-f6 the onscreen software indicators seems to work but no lights from Leds comes on.
I checked and rechecked the flat cable for backlit, reset the SMC many times, redid all the unmounting and remounting of the Optibay, but no success........ 😟
Any ideas ? Any progress from your side ? Should we run out to a service center ?.. With no apple care sounds expensive..... sad that there is no pictures of all the complete cabling....any more detailed informations ???

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Answer 4

Dec 5, 2010 4:16 PM in response to RDucci

Hi guys,

I actually did this MCE optibay mod back in May 2009 and had the exact same LED issue.

I poked around and then gave up.

I'd buy a new top case if I thought that would fix the issue, but with you all having the same issue I'm beginning to wonder.

Any ideas? I'd like to have the backlight working again. 😀

Henry

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Answer 5

eww

Level 9

53,052 points

Oct 27, 2010 4:56 AM in response to penguinn

Apple does not publish any schematics or related descriptions even for its own technicians, who never do repairs of the kind you've undertaken. I'm afraid you're completely on your own.

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