MacBook Pro Unibody - No Backlight - Logic Board Question

MBP 13 2011 Video and Backlight circuit paths

Hello,
Great Forum.
I have a 2011 MBP 13" logic board 820-2936-B with a black screen. The system will post and display is good on external monitor. In the Video connector area A small black resistor/capacitor? was missing. Two components had a damaged foot. marked KNP Y3 AND S8, lastly the 40 pin video connector was damaged slightly. using a IR rework system I replaced the connector and the three components. All fuses are tested good. I am still getting the same issue. Black screen but working with an external monitor. I would love direction to the video circuit on the logic board? or pictures showing proper voltage points or resistance measures for the video and backlight circuits. Sounds like the WLED driver is a typical backlight failure, is there a typical video signal failed component. Liquid damaged cleaned with ultra sonic bath using A1 solution.

Thanks in advance.
 

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Sheridansystems said:
Hello,
Great Forum.
I have a 2011 MBP 13" logic board 820-2936-B with a black screen. The system will post and display is good on external monitor. In the Video connector area A small black resistor/capacitor? was missing. Two components had a damaged foot. marked KNP Y3 AND S8, lastly the 40 pin video connector was damaged slightly. using a IR rework system I replaced the connector and the three components. All fuses are tested good. I am still getting the same issue. Black screen but working with an external monitor. I would love direction to the video circuit on the logic board? or pictures showing proper voltage points or resistance measures for the video and backlight circuits. Sounds like the WLED driver is a typical backlight failure, is there a typical video signal failed component. Liquid damaged cleaned with ultra sonic bath using A1 solution.

Thanks in advance.
Click to expand...

I might be wrong but it looks like the LVDS connector is a little to far back in its pad, also it doesn't look like there is a lot of solder on the legs of the LVDS connector either, this could be part of your problem.

The WLED Driver is the little QFN package to the right of the connector looking from the view you posted in the picture " U9701 " on the schematic and board view file. I dont think the 2 things you pointed out that were missing had anything to do with the black screen problem I looked at them on the board view and they don't connect to the LVDS or the WLED Driver that I can see anyway. I would make sure that fuse for the backing is good before doing anything else.

Do you have the schematic and board view?
 
l0l0pr said:
I think it is the Early 2011 15" MBP 8.1, it has the 2.2 i7 with the Radeon HD 6750M.
Click to expand...

Yea it is the 820-2915-B logic board, I don't have the schematic for this board but I am sure it is out there somewhere. Just google it and see what you come up with.
 
tswartfiguer said:
I might be wrong but it looks like the LVDS connector is a little to far back in its pad, also it doesn't look like there is a lot of solder on the legs of the LVDS connector either, this could be part of your problem.

The WLED Driver is the little QFN package to the right of the connector looking from the view you posted in the picture " U9701 " on the schematic and board view file. I dont think the 2 things you pointed out that were missing had anything to do with the black screen problem I looked at them on the board view and they don't connect to the LVDS or the WLED Driver that I can see anyway. I would make sure that fuse for the backing is good before doing anything else.

Do you have the schematic and board view?
Click to expand...
You're Right! Good eye. I set the LVDS back a bit to connect with a trace I exposed after I tore off a pad pulling off the old LVDS. I just got a IR rework station and it was my first lift on a working logic board. I figured it would be a little easier to bridge a connection if the LVDS were closer to the trace. sure enough I needed just a little more solder. After reflowing each of the 40 joints. I have back light and video signal! too cool! :cool: Will see how the rest of it is when I load the OS.
You mentioned the components I replaced were not of the video or backlight circuit. should I be looking for issues anywhere in particular with those ic's?
Great forum ! and Thanks tswartfiguer!!!!:D
 
Sheridansystems said:
You're Right! Good eye. I set the LVDS back a bit to connect with a trace I exposed after I tore off a pad pulling off the old LVDS. I just got a IR rework station and it was my first lift on a working logic board. I figured it would be a little easier to bridge a connection if the LVDS were closer to the trace. sure enough I needed just a little more solder. After reflowing each of the 40 joints. I have back light and video signal! too cool! :cool: Will see how the rest of it is when I load the OS.
You mentioned the components I replaced were not of the video or backlight circuit. should I be looking for issues anywhere in particular with those ic's?
Great forum ! and Thanks tswartfiguer!!!!:D
Click to expand...

I am not sure about the other components you replaced. I I had to make a guess they might be parts of the Ethernet circuit. If I get a chance today I will look into for you, but check your schematic and board view, Use the short feature in the board viewer app to see where each side of the components you replaced goes.

And congrats on your repair thats awesome glad I could help. I wish my issue was that easy to fix on my board. No one has answered my request for help about my sensor issues.

My board, if I plug my battery in the CPU stays at near 100% usage for the kernel task in activity monitor. But if I run the system without a battery it runs ok. Also my system doesn't go to sleep when I close the lid. And powers on as soon as I plug my magesafe in without even pressing the power button. I am lost on these issues. If there is someone that can help please let me know what to check. Thanks in advance.
 
tswartfiguer said:
Yea it is the 820-2915-B logic board, I don't have the schematic for this board but I am sure it is out there somewhere. Just google it and see what you come up with.
Click to expand...

I have been doing that but to no avail. :eek: But I will keep searching. Thanks for your help.
Regards,
Tito
 
Same problem with 13 late 2011 as anatomij818

Hi
I have a MBP 13, late 2011.
Charging system works fine. But when power up the fan start to speed from slow to high speed. No other signs of life.

Regards Jørgen
Copenhagne Denmark
 
Dadioh said:
Those last three pins are the backlight pins so at a minimum you need to replace the LVDS cable. You also need to look inside the LVDS connector because it is possible that the interior pins are also corroded or plastic melted in that corresponding connection.

The fuse is identified in my attachment. That is likely blown.
Click to expand...


Hi again Dadioh,

Can you give me a part number for that fuse? Or perhaps point me in the right direction of trying to find it?

Thanks again!
 
l0l0pr said:
I give up, after many hours of searching I can't find the capacitor nor the IC. :mad: I believe the schematic is not dumb proof. :eek:

Thanks for all your help!
Tito
Click to expand...

are you using the board viewer and the board view file to locate the IC and capacitor. I dont know if you know or not but the capacitors are like brownish yellow in color and the 0420 size capacitors are very small. If you not useing the board view file you will never find it. It is in the zip file posted above. Dont give up either it is hard but it all can be done. Sometimes you just need the right tools. what is the capacitor number you are looking for anyway? should be "CXXXX" x being the numbers after C maybe I can help find it
 
No backlight fuse OK what to test more?

I just started the investigations for a MBP A1278 with no backlight issue, what i have to test step by step to be sure it is a WLED driver problem or not?



1) The fuse with the tiny dot o top is ok
2) Just tested the tension on the working machine with max brightness and the reading on the Diode 74 is about 13V instead of 27V.

What's next step?
Thanks for your support :)
 
Macbook Pro A1297 mid 2010 , fuse problem ?

Hi,

Stumbled accross this thread, and must say: It's great ! :)

I've got a Mid 2010 Macbook Pro 17" 2.53Ghz ( A1297) with probably water damage. Works fine on an external screen, but backlight is bust ( see the picture with a flashlight)

Because the A1297 pictures I've seen already in this thread don't match my type I wanted to share the location of the fuse.

See attached picture, it's at the back side of the logic board ( you need the remove the speaker assembly first).

When checking the fuse with a multimeter ( at the 2000k setting I believe) I get "1" of at moments 1400-1600. But NEVER "0". EDIT : The left edge looks a bit "jagged"..

Does this mean the fuse is bust ?

When I measure the chip to the left of it (with the 6 legs) I get 300k accross the most right 2 legs.. That means that WLED driver is ok ? EDIT: Attached second picture marking the pins..

Thnks for the input !

I'm a bit hesitant to start soldering right away, even to quickly bridge the fuse to check if that´s the problem.
 

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Don't jump that fuse. You risk letting the smoke out of your circuit.

The fuse if good will read the same as when you touch your probe tips together.
 
triplelucky said:
Don't jump that fuse. You risk letting the smoke out of your circuit.

The fuse if good will read the same as when you touch your probe tips together.
Click to expand...

triplelucky is right you should never bridge a fuse, fuses are there to protect what is further down the line, there is always a reason for the fuse to blow and bridging the fuse will only allow the voltage spike the blew the fuse to reach what the designer of the board didn't want it to reach. Bad news, bad things can happen for what only cost a couple buck to replace the fuse will save you a lot of heart ache.

Just list triplelucky said if the fuse has continuety or measures near 0 ohms it is good, if you read it at very high ohm reading then it is bad. If your multimeter has the continuity test and it beeps when you probe both sides of the fuse then it is good.
 
triplelucky said:
Your IC looks like U7400 and the capacitor should be C7521.
Click to expand...

Hi triplelucky, thanks for looking into it, I also think the U7400 is the correct one but I'm not yet 100% sure since I don't have the board view file. On the capacitor I was not able to even get close to finding it so thanks a lot for pointing it out.

tswartfiguer said:
are you using the board viewer and the board view file to locate the IC and capacitor. I dont know if you know or not but the capacitors are like brownish yellow in color and the 0420 size capacitors are very small. If you not useing the board view file you will never find it. It is in the zip file posted above. Dont give up either it is hard but it all can be done. Sometimes you just need the right tools. what is the capacitor number you are looking for anyway? should be "CXXXX" x being the numbers after C maybe I can help find it
Click to expand...

I don't have the view file (I have look all over but no luck) so till I find the view file, I will put any attempt in fixing the board on hold. I found a website www.laptop-schematics.com but don't know if it is a legit site and if anyone has dealt with them and can share their experience, your help is appreciated.

Once again, thanks for your time and help.
Tito
 
triplelucky said:
Don't jump that fuse. You risk letting the smoke out of your circuit.

The fuse if good will read the same as when you touch your probe tips together.
Click to expand...

Hi, I'm planning on placing a new fuse (possibly a bigger one in size than a 0402 because there is enough room, but same specs).

For now I want to know if it's only the fuse. The readings from the chip (300k) tell me the rest is fine. I believe because of some minor water the fuse did it's work.
 
Macbook Air 2010 A1369 with Backlight Issue

Hello Friends,

I have a Macbook air 2010 that has backlight issue. Below is what I found:

1. The fuse is out. I can replace that.
2. the pins 1,2,5,6 of the MOSFET Q9806 seem to be short with the ground some where. these pins together form the signal PPBUS_SW_LCDBKLT_PWR (per diagram below).
3. I traced the PPBUS_SW_LCDBKLT_PWR hoping that there must be some component that is likely short with the ground and causing the Q9806 output pins to be grounded and removed the capacitors C9712 and C9713 but no luck.

I can't tell what could cause the Q9806 output pins to be shorting; any help would be great. I am attaching the two pictures that show what I have done and seen so far.

Any advise would be great. I hope it is not the WLED driver as would be difficult for me to change it.

Many thanks!
 

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A1286 820-2915-A keeps blowing backlight fuses!

Hi guys,

I have done my best to read through all of these posts, and with their help, have located one of the fuses that power the black light on my MBP 15 I7 A1286 with a MOBO of 820-2915-A

Attached is an image of the underside of the board where I was able to locate a blown fuse (marked with a "p" near the tip of my tweezers) and I have successfully replaced it with a new 2a fuse.

When I put everything back together (making sure the battery was last and LVD plugged in first) I blew the fuse again upon powering back on again. (I did have the mag plugged in if anyone is wondering)

So my question is: is there another fuse? I found a white smd near the mag jack that has a "U" / U with an underline on it, but I am not sure if it has anything to do with this. *doubt it*

Where should I go next with this? find the other fuse? or start at the LED driver?

If the LED driver, is that the qfn to the right of my tweezers? it reads 09AQ D68B and is about 2 millimeters square.

Is there a component I can measure resistance / currant across to check things?

I only have 4 fuses left as I keep loosing them or blowing them ha!
Also if anyone has schematics that would be wonderful.

I hope the LED driver is not the QFN next to my tweezers because it looks like it would be twice as hard to work on then in Louis Rossmann's video's

Thanks in advance!
-Chad
 

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