MacBook Pro Unibody - No Backlight - Logic Board Question

[qaiser57]

Macbook A1278 N-PRO-Logic Board

Thanks for the feed back.
this resistor 1.2M mounted in between Pin 9 of Wled and pin 21/22 of LVDS,the Pin 9 has 0v and pin21/22 of lvds has 12.5v( sorry for the error in previous thread because I assumed it as a diode but in fact it is a resistor as confirmed by you) please indicate the location of boost diode.
thanks

Is that connected to pin 9? If so there are 2 resistors hanging off pin 9 which is the VSEN signal for the WLED driver. This is how the driver knows what voltage it is putting out on the cathode of the boost diode. A 1.2Mohm in an 0603 package and a 71.5kohm in an 0402 package. That looks like an 0603 package so my guess is that is the 1.2Mohm resistor.

If this resistor is damaged then it would mess up the feedback loop and the WLED driver will probably stop boosting the voltage.

According to the resistor marking guidelines this is indeed 12 plus 5 zeroes = 1.2Mohm marking.

http://www.niccomp.com/Products/smt/NRCNRSNPartMarkingGuide.pdf

 

[Dcuchillas]

Hey dalioh, i have the multimeter but m friend couldnt help me out, he just handed it to me.

Its similar to this one: http://i00.i.aliimg.com/photo/v0/236917984/YX1000A_Analog_Multimeter_Analog_AvoMeter.jpg

My friend told me that it should be in x10 to measure ohm, can you explain me which of the two (red or black) do i need to use to measure the fuse, and where do i need to place the other one.

 

[Dcuchillas]

Hey dalioh, i have the multimeter but m friend couldnt help me out, he just handed it to me.

Its similar to this one: http://i00.i.aliimg.com/photo/v0/236917984/YX1000A_Analog_Multimeter_Analog_AvoMeter.jpg

My friend told me that it should be in x10 to measure ohm, can you explain me which of the two (red or black) do i need to use to measure the fuse, and where do i need to place the other one.

Hey dadioh i managed to do it, if i place the tip exactly on the white dot it reads aboit 30, same on one side, in the other is about 10. Wha does that means???

 

[Dadioh]

Hey dadioh i managed to do it, if i place the tip exactly on the white dot it reads aboit 30, same on one side, in the other is about 10. Wha does that means???

You need to put the black probe on one side of the fuse and the red probe on the other side of the fuse to measure the resistance through the fuse. Make sure the 2 leads are not touching each other. Also make sure you disconnect the macbook battery before probing on the board.

 

[Dcuchillas]

You need to put the black probe on one side of the fuse and the red probe on the other side of the fuse to measure the resistance through the fuse. Make sure the 2 leads are not touching each other. Also make sure you disconnect the macbook battery before probing on the board.

Hey thanks. The needle doesnt move, while on other fuses it does. I guess because this meter doesnt measure megaohm, it starts on 1k of ohm which i suppose it's a megaohm. so pretty much its blown right??

 

[Dadioh]

Hey thanks. The needle doesnt move, while on other fuses it does. I guess because this meter doesnt measure megaohm, it starts on 1k of ohm which i suppose it's a megaohm. so pretty much its blown right??

If the needle doesn't move then the fuse is blown. You need to find someone who can replace it. Soldering those small parts is tricky if you don't have experience. Some people on this thread have shorted out the fuse but I don't recommend it. If the fault that caused the fuse to blow is still there then you will smoke other parts.

 

[Dadioh]

Thanks for the feed back.
this resistor 1.2M mounted in between Pin 9 of Wled and pin 21/22 of LVDS,the Pin 9 has 0v and pin21/22 of lvds has 12.5v( sorry for the error in previous thread because I assumed it as a diode but in fact it is a resistor as confirmed by you) please indicate the location of boost diode.
thanks

Oops. The boost diode on the Pro models is on the front side of the board so it is easy to get to. On the non-PRO the boost diode is on the back of the board which isn't too convenient. The good news is that you can measure the same point at the location shown in my attachment. It is the same point. This point needs to be 27V at max brightness if the WLED driver is working properly.

 

[Dcuchillas]

If the needle doesn't move then the fuse is blown. You need to find someone who can replace it. Soldering those small parts is tricky if you don't have experience. Some people on this thread have shorted out the fuse but I don't recommend it. If the fault that caused the fuse to blow is still there then you will smoke other parts.

Hey thanks man! i really apprecciate it.
I have already ordered the fuses. but since i'm on el salvador, it will take like 2 weeks to get them here. I'm contacting some techs who can fix it for me.
I will let you know how everything work.
Thanks man! YOU ROCK!

 

[qaiser57]

Macbook A1278 N-PRO Unibody 13.3 inch-Logic board

Hi,

Today i got some time to work on macbook,as indicated to you in previous thread the resistor 1.2m found burnt and I replaced it, and does not make any improvement.
The voltage at boost diode is 12.5v.I failed to get the source of 27v on logic board, what is the conclusion now that wled is blown???it sucks

Oops. The boost diode on the Pro models is on the front side of the board so it is easy to get to. On the non-PRO the boost diode is on the back of the board which isn't too convenient. The good news is that you can measure the same point at the location shown in my attachment. It is the same point. This point needs to be 27V at max brightness if the WLED driver is working properly.

 

[Dadioh]

Hi,

Today i got some time to work on macbook,as indicated to you in previous thread the resistor 1.2m found burnt and I replaced it, and does not make any improvement.
The voltage at boost diode is 12.5v.I failed to get the source of 27v on logic board, what is the conclusion now that wled is blown???it sucks

Quite possible that whatever event took out that resistor also took out the driver. Sounds like the driver needs to be replaced

 

[Khilil]

MacBook Air no backlight

I was wondering if u could he me find the fuse on my MBA. After water spill I have no backlight, but everything else works! Thanks

http://guide-images.ifixit.net/igi/65SK3LDBAlNIdocP.huge

 

[Dadioh]

I was wondering if u could he me find the fuse on my MBA. After water spill I have no backlight, but everything else works! Thanks

http://guide-images.ifixit.net/igi/65SK3LDBAlNIdocP.huge

I have never worked on an Air before but looking at that photo I don't see the WLED driver near the LVDS connector (upper right corner). Is there a closeup shot of the back side of that logic board? Also, the fuse is quite a small device so I need an even more detailed photo than you have linked. It may be easier for you to spot it yourself. In the previous models they have always used a beige component with a white dot. Armed with a magnifying glass you should focus your attention on the front and back of the board near the LVDS connector.

Of course, there is always the chance that they used a different circuit on the Air to drive the backlight. I can't rule that out.

 

[Khilil]

Look at this two pictures and see if you can locate the fuse. Let me know if I need to take a better picture or if I need to focus somewhere else

http://i1089.photobucket.com/albums/i343/Khilil83/1c56a7f2.jpg
http://i1089.photobucket.com/albums/i343/Khilil83/1078c189.jpg

 

[Dadioh]

Look at this two pictures and see if you can locate the fuse. Let me know if I need to take a better picture or if I need to focus somewhere else

http://i1089.photobucket.com/albums/i343/Khilil83/1c56a7f2.jpg
http://i1089.photobucket.com/albums/i343/Khilil83/1078c189.jpg

hmmm... pretty scary looking liquid damage

First step is to really clean up that board with isopropyl alcohol and a brush. The LVDS connector itself should be removed and carefully cleaned.

It is possible that the 25pin QFN package at the top is your WLED driver but I can't read the numbers on the device. Also, I am not sure if the pinout on the LVDS connector is the same as on the Macbook Pro.

If you are able to locate a schematic for this I could have a better look at the circuit and find out where you should be measuring for the LED voltage to the backlight.

 

[Mr. PoopyPants]

Thank you so much Dadioh and others for all the research that went into this thread!

Question: where can I track down schematic diagrams for a specific model? I'm looking at diagnosing a similar problem with my mid 2009 MacBook Pro (A1286 / EMC 2324), and I'd like to be able to assess a relevant diagram. The one on the first page was nice and easy to use, but my layout is slightly different than the late 2008 model.

 

[Dhelsdon]

My A1151 is having a similar issue, the keyboard backlight is half working, one side is bright the other side is quite a bit dimmer. I am familiar with the internals as I've done multiple hard drive swaps, and upgraded the airport card. I do have a multimeter so I can test stuff If I know what's what.

Any help appreciated.

 

[Dadioh]

My A1151 is having a similar issue, the keyboard backlight is half working, one side is bright the other side is quite a bit dimmer. I am familiar with the internals as I've done multiple hard drive swaps, and upgraded the airport card. I do have a multimeter so I can test stuff If I know what's what.

Any help appreciated.

That is quite a different topic. I have worked a bit with the backlight keyboards on the unibody (you can retrofit the Macbook Pro backlight panel into the unibody Macbook). The unibody uses a flexible panel just behind the keyboard and connects to the logic board with a small flex connector. I am not sure of the older MBP models if they use the same technology.

If one half is dim but not off then it sounds like the connection to the logic board has an issue. Maybe some corrosion? See if you can trace that connector down and examine closely.

 

[astroboyid]

thank you it work i done this before with dsi i was easy to me thanks again to all upload pictures was easy to find it this way

late 2009 macbook pro 13 cost me $300 as is part on ebay great deal

 

[Mr. PoopyPants]

I think I'm in the proper vicinity for the photo on the left. Included a second photo as a reference point for where I am on the logic board. Yes, I do still need to clean off the back side of the logic board.

Am I correct to assume I should test the component with the white dot right around the center of the left photo for the appropriate resistance?

 

[udawat]

No Display - Black Screen

I have a MacBook Pro 13" Unibody A1278 2009 model. When it is started, the display does not show up but a background light can be seen and can be controlled with brightness buttons (F1, F2). Everything else works fine and it is right now connected to an external Sony Bravia.

It reached its present condition after several mishaps.
September 2009 - bought
December 2009 - Stepped on it - cracked Front Bezel/Panel. But LCD worked fine with no glitches.
June 2010 - Spilled water on lower half (Keyboard and Trackpad) - Immediately turned the macbook upside down and pressed the power button for some time to shut it down (phew!) - I think that is why the sensor below trackpad turned Pink. But still, the display was working after i had let it rest drying for 2 days.
August 2010 - One fine day, the display started to flicker (On/Off - come and go randomly) and finally the same day it died. Of course a background light was still there which could be controlled by brightness keys F1, F2.

Now what i had achieved so far with it is:
I ordered a new Front Bezel/Panel from iFixit and was going to put it in place of the cracked one but the same day the display died on me (August, 2010) so i had the cracked panel removed and the new panel waiting in box.

Then, on January, 2011 - I ordered a 13" Unibody LCD Panel Glossy from iFixit. I replaced it with the old one but still it did not worked. The LVDS cable used was the old one. Still, no video but still the same background light.

Then, when i could not figure out what was the problem, i decided to call my friend with the same Macbook model as mine. We opened up our display assemblies. So, I had my whole display assembly - new LCD panel with my old LVDS Cable connected to his working motherboard and voila it worked seamlessly. Then, he connected his display assembly with mine and it was the same problem, no video.

So, since i have told this forum my whole story, is there any fix?

 

[Yako76]

Driver

went ahead and replaced the driver.

Success!!

thanks Dadioh

Hello Asma123,
you wrote you replace the driver LP8543SPQ. In the Schematic of this board is the driver LP8543SPQX. Do you mean ther is a several difference or I can replace the driver like you?
Thanks a lot for your Feedback!

 

[Goonies]

Also success!!!

Hello Dadioh and the others,

two weeks ago, I got a drowned MacBook Unibody Alu 2,4GHz...
At first I disassambled the mainboard to look around for some defective parts.

I've seen a part with the sign "F09 - 6A" and thought it would be a fuse. I shorted this "fuse" by a 6A-Wire...

Later I discovered a mini-board with the battery-state LEDs and the little switch on it, what was completely destroyed by the water spill and the hight currancy of the full loaded battery, directly after the water spill...

OK, after disconnecting this tiny board the MacBook was OK, but the backlight wasn't.
I found your thread and was so happy, because I suddenly did not feel alone anymore!
There were so many good and very good tipps in it, that I hardly dared to believe my luck!!!
But on my way to find the probs of the backlight, I tested the real fuse of the backlight – it was OK.

Now, at the end of the thread, I learned, that the "fuse" is the boost-diode of the backlight. I eliminated the shortwire and? The backlight is OK!!! The complete Macbook works again!

Have many, many, many thanks for your very great job!!!

At the next step I'll try to reanimate my old 1,5GHz PowerBook, what has a defective VRAM... I hope to get in that case even so good and engaged Guides?! We will see

Best Regards and once again: 1000 thanks
Georg

 

[vyrcoop]

13 Macbook Pro mid 2010 A1278

Hi, first of all, thank you all (mainly Dadioh of course) for this great thread.

My problem is basically the same as most of you - non working backlight, everything else seems fine. I bought the macbook from ebay as AS-IS, though that I will replace the screen, however I found out, it was spilled on it... than found this thread and read all through it. But I never found exactly the same model as mine (13 Macbook Pro 2,66GHz, mid 2010), so here's the picture:

http://dl.dropbox.com/u/2635790/quIfTtoLygA1pOSJ.jpg

Can anyone confirm, that I marked the components right, please? (I'm pretty sure about all of them except the boost diode.)

I measured the fuse (or what I expect to be a fuse), but it seems ok (closed circuit, very low resistance), so that leads me to conclusion that the WLED driver is damaged. However I don't really know how to proceed from here, how to make sure it is damaged, because it's a bit different component that was talked about in this thread (mine is LP8545 versus LP8543 which is in the previous macbook models...).

Also I'm a bit worried about the WLED availability... I checked the newark.com, digikey.com and avnetexpress.avnet.com but non of them have the component in stock
Anyway, I read a lot of success stories, so I'm hoping for the best.

Any ideas?

LP8545 datasheet (my model)
LP8543 datasheet (previous models)

 

[alexfunari]

Hi guys, noob here. Trying to understand this thread. I have a MBP 15'' A1286 core2duo model. I'm having the same issues, but i suspect its my fuse. I have all the tools necessary to check, however, i cannot locate the fuse. I can supply pics of the board if necessary!

Please help!
Thanks!

 

[Dadioh]

Hi guys, noob here. Trying to understand this thread. I have a MBP 15'' A1286 core2duo model. I'm having the same issues, but i suspect its my fuse. I have all the tools necessary to check, however, i cannot locate the fuse. I can supply pics of the board if necessary!

Please help!
Thanks!

Welcome to our thread

Take some detailed pictures as high resolution as possible of the front and back of the logic board near the lvds connector. I will try and spot the fuse for you.