Mid 2009 Model A1278 / 2.26 or 2.53 GHz Core 2 Duo processor EMC 2326

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Detailed Logic Board Question. No Backlight.

I obtained a Macbook Pro 13 unibody with non functioning display (everything else works). I took it apart ad discovered that the LVDS cable end was completely destroyed. I ordered a replacement display assembly (complete with LVDS cable). I now have an image but no backlight.

Upon close examination of the components surrounding the LVDS connector I notice I have a component missing compared to a detailed photo of the same motherboard that I found on the net. I am not sure if this component might be a fuse that has been removed. I am trying to find someone who has one of these logic boards accessable that can identify what this part is supposed to be. I can provide a picture of the area of the board showing the part.

Answered! View the answer I have this problem too

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Without a picture indicating what part you're missing we don't have a clue how to identify it.

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http://img826.imageshack.us/img826/1204/...

Here is a picture. Doesn't seem to be a way to add pictures directly on ifixit unless I am missing something.

The part circled in red is missing on my logic board and under magnification it looks like it "may" have been on teh solder pads at one time. Given the white body I think it is possible that it is a fuse but I suppose it could be a resisitor. I don't think I have ever seen a cap in white.

Anyone with one of these boards out in the open could put a meter across it and tell me the resistance???

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No one have a MBP 2009 open and could measure this for me?

I checked the voltage on both sides of the pads with the machine running and it is zero Volts on both sides. Makes me think it can't be a fuse....

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OK. I am a little closer now. It turns out that this is a capacitor. Given the white body it might be a tantalum cap. One side is ground and teh other is probably driving the LED backlight. It measures 27V with display on regular brightness and drops to 14V when the screen dims. When you shut off the machine it slowly drops to zero as it discharges.

Next step is to determine what value the cap is and to see if I should have 0 volts on it when it is not populated. Feel free to chime in with opinions here....

http://img824.imageshack.us/img824/6347/...

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Found the reference circuit for the National Semiconductor part and my guess is that this cap is the 4.7uF Cout in the datasheet. Now I just need to trace through the circuit and see if there is anything open circuit feeding the cap. Then replace the cap and cross my fingers.

Hopefully this info is helping others here who might have no backlight on their LED displays.

http://www.national.com/ds/LP/LP8543.pdf

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Deck the Halls
With tools and Fix Kits

6 Answers

Chosen Solution

This is solved. Turns out the WLED display driver chip was internally shorted to ground. That in turn blew the 2A fuse that fed the P channel FET that drives the power to the boost circuit. Replaced the LP8543 device and then the 2A fuse (tiny 0402 package) but still did not have a backlight. Started probing around and discovered that the enable pin for the LP8543 was low. They use a 300K / 100K resistor divider network to get the 3V enable. My 300K resistor was open. Replaced that and BOOM I have a backlight. And that missing device is a capacitor on the output of the boost. Considering the hours I put into this it hardly seems worth it but I rescued this board from the landfill anyways :-)

Soooo there you have it.

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Great job--now please accept your answer to clear the question. Thanks Ralph +

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Very interesting David. I was sure the small white capacitor was a microfuse so I learned something today. +

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Hello, my 2.4 ghz macbook pro a1286 15 inch, has the same problem, the backlight is dead, I tried a new screen and I connected to the LVDS connector, after this experiment I'm forever the backlight, I do not know where to start your search for the fault, one thing is for sure not get power to the ribbon of the backlight on all the threads, no one has a wiring diagram for this model? thanks Luca

Hi,the unibody 15 a1286 is totally different,don't have similar schematic,the bost chip of led backlight is other brand,regards

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Hello,

it looks like I've the same problem. Macbook pro unibody 13". I recovered a totally nonfunctioning liquid spill with success. Only

the backlight is not working. With an external Monitor the MacBook works perfect. I also can see the picture on the internal LCD in a strong light.

Can you support me with a circuit diagram / identification of the components on the PCB? Where can I measure if the driver is working or not? I did not identify the 2A fuse-where is ist placed? Can you mark it in the pictures? There is also the possibility of the connector beeing damaged but I also do not have the pinout of the connector.

I really appreciate any support.

Martin

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greeting i have the same problem my macbook pro 13' great with external monitor i really would like the pic so i can see what are the parts that i need also the parts # and where to buy them... i really appreciate alexander

asm@embarqmail.com

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I have the same problem with a liquid damaged 13 inch macbook pro - display works but no back light

I also need the same information to do the repairs that were requested by Martin Schaller

Gil Yetter - gilyetter@austin.rr.com

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Hi, I also have the same problem with my Macbook Pro 13" 2.4Ghz 2010 model. I have taken photos of the logic board which is different to the pictures posted above. http://i1206.photobucket.com/albums/bb44... The only white capacitor that looks anything like the one in the above images is this located near the battery connector http://i1206.photobucket.com/albums/bb44...

http://i1206.photobucket.com/albums/bb44...

Can anyone advise where to find the correct capacitor

Many Thanks.

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It is not a capacitor that is the issue. The white component in your picture is probably a fuse. What you are looking for is a tiny fuse, beige in color with a white dot on the top. It is an 0402 part so basically like a pepper spec. Magnification helps. Look near the LVDS connector.

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Thanks David for getting back to me. I've taken some more photos around the LVDs connector to see if you can identify the correct part that needs changing. Last thing I want to do is make the issue worse.

Thanks again.

http://s1206.photobucket.com/albums/bb44...

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These "me too" questions just don't get answered as it's tacked onto an already answered question and no one looks at it. PLEASE start a new question.

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The fuse is actually on the back of the board. Flip it over and take a shot near where the LVDS connector position is (on the other side). You will see a small beige part with a white dot on it. I just verified it on a spare board I have here. I took a shot through my microscope and can upload later if required but it should be obvious when you look on the other side.

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Thanks, if you could upload a photo that would be great. Thankyou.

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dadioh will be eternally grateful.
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