13" aluminum unibody, 2.0 or 2.4 GHz Core 2 Duo processor.

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Back-light still doesn't work after a lcd panel replacement

Hi,

Gday! I am trying to repaire back-light problem on my MacBook A1278, i have installed a new screen but the back-light still doesn't work. I could see the desktop under a very bright lamp and when i connect the MacBook to an external monitor, everything works! So it shouldn't be problem with the logic board.

The problem is, i think it must be problem of the new lcd panel or the lvds cable. But how could i test them to identify which one is going wrong?

Update

I had tried to replace the whole display assembly several months before, but it still didn't work after the repair work. So, i identified it as a logic board failure and sold it on ebay at the price of a mac mini.

Now, i am happy with new macbook pro:), i suggest you to sell it directly if change of lcd panel can't work it out, then buy a brand new one.

Answered! View the answer I have this problem too

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Wait for an answer from leemise or bac, they're the experts on this type of problem.

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has anyone fond the solution yet? i have the same problem...

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I'm having the same problem, has anyone resolved where to find the specific LVDS cable?

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I am in the same situation.

Although, I spilled water on my Macbook Unibody (not the newer 'pro' editions). Everything works perfectly, keyboard, trackpad, keyboard backlights, sound.... I can also see the screen under a bright light, or all works perfectly when I plug it into a monitor.

My screen has been replaced but still no avail, The company that tried to fix it said it was a problem with my Logic Board.

It's so annoying that my whole laptop is working but its just the %!*# light that isn't working! And the only option is a new Logic Board apparently.... Might as well get a new laptop for that price...

Has ANYONE found ANY other solutions?????

Please let me know, I would really appreciate it if you took your time to help!

Thanks!

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9 Answers

Chosen Solution

To those of you who have no backlight on an LED lit macbook -

The problem is most likely related to the WLED driver on the logic board not supplying power. Power output from the WLED driver ranges from something like 18-26 volts. most other circuitry on the board runs at 12v or less, so liquid spills do not damage other parts on contact.

your lvds cable is most likely fine. there is a fuse on the logic board that runs the WLED driver. it is normally located close (within 2cm) of the lvds connector, and is a 0402 package (the smallest on the board, will look like a surface mount resistor or capacitor). on my macbook (nonpro, 13.3") it was a brown fuse with a small white dot in the center. can also be black, or have an "f" in the center. measuring both sides of this fuse with the macbook power on should read 12v. if not, the fuse is bad.

you CAN just remove the fuse and close the circuit with a blob of solder, however if there is still a short in the system (remaining traces of liquid spill, residue, etc) and you short this fuse, you will destroy the WLED driver chip. these need to be replaced by a micro electronics professional, with a hot air gun and microscope.

your best bet is to find someone good at soldering (very, very small) and order some replacement 0402 package fuses and solder in a replacement.

if the fuse is good, pin1 of the wled driver should be receiving ~3v to power up the wled driver. if fuse is good and still no output from wled driver, then the wled driver itself is most likely damaged.

you can search around the net, there are a few chinese forums with schematics and pictures of the macbook logic boards to help you with this.

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I agree, and I have found this fuse to be blown on a number of unibody MacBooks. Bridge the fuse, and you have a backlight. Here's a thread which gives some more details: http://forums.macrumors.com/showthread.p...

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On some models the fuse is on the opposite side of the board but in the same proximity, with in 2 cm of being directly under the lvds connector.

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Hi Matri, first why did you replaced the screen ? Was the MacBook dropped ? Broken hinges ? Liquid Spilled ? For sure this is not a video problem since you see the desktop on screen. It's a lightning problem probably related to the inverter circuitry, backlight lamp or logic board. Most of the time the lightning problem is caused by a bad inverter cable or inverter board so to troubleshoot the computer you should have these two parts in hand. The logic board or the backlight lamp could also be the culprits if the machine has been dropped or liquid spilled. There are components on the logic board that bring power to the inverter board so a broken hinge may have shorted the inverter cable in the hinge blowing the inverter circuitry on the logic board. Liquid spill could also affect the lightning circuitry on the logic board.

First thing to check is the inverter cable connection to the logic board then the two connections to the inverter board (the inverter cable connector and the backlight connector).

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Thanks for the reply, but this model doesn't has an inverter. i did nothing to this poor machine, the backlight suddenly dead several days ago without any advance sign.

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Did you replace just the LCD Panel, or the entire assembly? This Model is LED Backlit, therefore no inverter, backlight or inverter cable. Power for the Display LED's ride along with the LVDS Cable.

since your getting display but not power, and both come from the same cable, its hard to determine without alittle troubleshooting.. replacing the cable would be a good start.. actually would have been the first step. a backlight problem would rarely be the LCD on this model.

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Yes, just the lcd panel, i couldn't find an suitable lvds cable on ebay, so i just guess it could be the lcd's problem, unfortunately it didn't solve my problem.

I am getting display without backlight, so i am a little confused about the situation, if the lvds cable has some problems, why it still can display? is it related to the logic board?

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I have two MBP Unibody LED LCD laptops with no back light. I have replaced with known good display and cable and still no backlight. External works fine. Image is on LCD but darkly with no back light. I wish someone would come up with a more productive answer so I can move on with this problem. If we could get some kind of schematic we could test for proper power to LEDs . Note Remember, leds are Light Emitting Diodes. They only light up when current goes one way. If power goes the other way it won't light up.

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I have nearly the same Problem. Liquid went between the display/logic Board connector and blow up 1-2 Pins.

The Display dosn't work. But I connect it to an extern display. It works. also I can see under a very bright lamp

I have to buy the complet display, because the display and the wire/connector is one piece.

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This backlight issue is becoming famous among Macbooks. I have replaced half a dozen in the last six months, but luckily I haven't had a failure due to faulty logic boards. I know it is not really a fix, but using an external display will allow you to use your Macbook. It does, however, contradict the point of having a portable computer.

Update

These 'toys' are such a hassle. I doubt if it is a logic board breakdown. It is more likely to be an issue with the inverter cable and/or incorrect installation of the new display. You must replace the inverter cable, the display and check all connections before blaming it on a logic board failure.

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Check the 13" Macbook Pro section to widen your net a little, because this version of Macbook seems to be very similiar to those.

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if anybody have soul the problem pls upload the picture and image so we can see

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I have the same problem. Lcd and lvds cable works fine on another machine. Mark Miller is right about WLED.

I'm still hoping for someone showing us how to fix this in detail with a video.

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Matri Ning will be eternally grateful.
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