MacBook Pro Unibody - No Backlight - Logic Board Question

[Dadioh]

Hi can someone shed some light on my MBP 2011 it has had liquid damage and this is the only issue I have see photo

Looks like issues with the LVDS signals to the display (I assume it doesn't do this on an external display?).

Check the LVDS connector for corrosion or damage. Unplug the battery before unplugging the LVDS cable. Be very careful with the LVDS connector... it is very delicate. Then examine it under magnification if possible. If it has corrosion or residue try cleaning with 99% pure Isopropyl Alcohol and a new toothbrush.

 

[Alexjones]

Sorry. The way he described the problem led me to believe that it would cost him big $$ to fix it. If its repairable and it can be done without costing big big $$, Go for it and please accept my humble apologizes. You have my blessings

 

[Dadioh]

Sorry. The way he described the problem led me to believe that it would cost him big $$ to fix it. If its repairable and it can be done without costing big big $$, Go for it and please accept my humble apologizes. You have my blessings

No problem. I thought you were being sarcastic. There are a lot of people that have rescued their Macbooks from the dumpster by using info in this thread. It is a very common issue and (sometimes) relatively easily resolved. Peace.

 

[Papabear60]

No problem. I thought you were being sarcastic. There are a lot of people that have rescued their Macbooks from the dumpster by using info in this thread. It is a very common issue and (sometimes) relatively easily resolved. Peace.

Hi Dadioh, I agree with you as a MB that just has a dim screen is 99.9% repaired but still not much use as a laptop which is frustrating !! Any ideas on my issue posted earlier this week as the WLED APP.1a appears to be enabled to boost the backlight to the required 27v but still doesn't?
I dont have a schematic so I am not sure what the other pins that are at 0v require. I used an earlier schematic you posted but it was for a MBP and may not be the same?

Any help to point me in the right direction would be appreciated

 

[Alexjones]

Hi Dadioh, I agree with you as a MB that just has a dim screen is 99.9% repaired but still not much use as a laptop which is frustrating !! Any ideas on my issue posted earlier this week as the WLED APP.1a appears to be enabled to boost the backlight to the required 27v but still doesn't?
I dont have a schematic so I am not sure what the other pins that are at 0v require. I used an earlier schematic you posted but it was for a MBP and may not be the same?

Any help to point me in the right direction would be appreciated

I bought Apple care for my older 2010 Macbook pro and i feel so secure. Hopefully i won't need it. My second macbook pro is 3 weeks old. I wouldn't even know where to begin if i had to repair my Macbook pros. Good luck.

 

[Dadioh]

I bought Apple care for my older 2010 Macbook pro and i feel so secure. Hopefully i won't need it. My second macbook pro is 3 weeks old. I wouldn't even know where to begin if i had to repair my Macbook pros. Good luck.

Wise choice. AppleCare is a good deal even if you have the skill and will to fix them just considering cost of parts. However, AppleCare does not cover liquid damage and 99% of the failed backlight are due to liquid spills.

Morale of the story is to not drink near your MacBook or leave drinks near them when cats are around

 

[Papabear60]

Dadioh,

I assume your are away or just way too busy to spend any time on this one, but can I just confirm the U9701 WLED driver pinouts you published earlier is the same as the app.1a??
Since this post I have also replaced the boost FET and still no 27v!
I think pin 7 at 0v may be my issue but without a schematic to confirm it is hard to make progress.
Any help would be much appreciated.

Thanks Dadioh for starting this thread as I have managed to educate myself a little bit on this dim screen issue and already found burnt enable pin resistors before needing additional help.
Macbook non-pro 13" Dim screen but image is present visable with flashlight
WLED Driver APP.1a is good as replaced earlier in troubleshooting
Fuse is good
12v on pins 21&22 on connector and boost diode.
WLED driver voltages:
pin1:0v
pin2:0v
pin3:12v (after burnt resistor replaced)
pin4:5v
pin5:6v
pin6:0v
pin7:0v
pin8:3.9v
pin9:0v
pin10:0v

I have 300k across pins 3&6 on the FET
Display and cable work fine with another good logic board.

Unless I am missing something (which I am perfectly capable of) the WLED driver has all the voltages it requires that have been discussed in this thread but I suspect the 0v on pin 1 "DRV"? which appears to come from the boost FET might be suspect but I read in earlier replies that the FET is not normally known to cause an issue.

Any help as to where to look next as I seem to have an issue not covered so far?

 

[Dadioh]

Dadioh,

I assume your are away or just way too busy to spend any time on this one, but can I just confirm the U9701 WLED driver pinouts you published earlier is the same as the app.1a??
Since this post I have also replaced the boost FET and still no 27v!
I think pin 7 at 0v may be my issue but without a schematic to confirm it is hard to make progress.
Any help would be much appreciated.

Sorry. I have been out in my forest all day cutting wood. Hope to look at this tonight. I emailed you something this morning.

 

[ipodfixit]

no backlight

I have a Macbook Pro A 1150 with no backlight, is the board similar to what you describe in this thread, I searched for this model number but found nothing. I will try and locate a fuse and keep a post of what I find. I have an ESD soldering station so will attempt repair once I find the problem.

 

[Dadioh]

Dadioh,

I assume your are away or just way too busy to spend any time on this one, but can I just confirm the U9701 WLED driver pinouts you published earlier is the same as the app.1a??
Since this post I have also replaced the boost FET and still no 27v!
I think pin 7 at 0v may be my issue but without a schematic to confirm it is hard to make progress.
Any help would be much appreciated.

The APP001 device is Apple proprietary so no data sheets available. But I have measured resistance to ground on a good one and published it earlier. Repeated below...

On Macbook 13 unibody aluminum non-Pro
Device APP001A

1 3.8M
2 100
3 9.9M
4 46K
5 100K
6 100K
7 >10M
8 49K
9 69K
10 >1M
11 >1M
12 >1M
13 0
14 >1M
15 >1M
16 2.8M
17 10K
18 15K
19 34K
20 30K


Pin 1 is the DRV to the base of the boost FET. If it is zero Volts then there is a problem.

Pin 2 is the Sense line on the Source of the boost FET. It measure the resistance across a pair of 0.4ohm resistors in parallel. I had one case where these resistors were blown open. You might check that. They are green in colour I believe.

Since you have power to the APP001 (WLED driver) and the enable pin is good it looks like it is something in the inductor/FET/Diode/Capacitor that provide the boost.

I can't send PM to you probably because you are new to the board? I did use the "send email" option so let me know if you got my message.

 

[Papabear60]

Yes a newbie ! so I will look why you cant pm me or email me - sorry as I probably havent set it up correctly

There are some differences
pin
1 2m
2 100
3 4.7k
4 28k
5 38k
6 100k
7 2.7m
8 32k
9 1.6k
10 2.5m

I'll do some digging around and report back.

 

[Dadioh]

I have a Macbook Pro A 1150 with no backlight, is the board similar to what you describe in this thread, I searched for this model number but found nothing. I will try and locate a fuse and keep a post of what I find. I have an ESD soldering station so will attempt repair once I find the problem.

I think the A1150 is pre-2007 model? In that case it isn't an LED backlight. It uses a CCFL to provide backlight and the most probable cause if yours is off is the inverter board. It resides in the hinge cover usually.

 

[hyugmyung]

greetings,

this is a wonderful thread.
one that also applies to my situation.

i have a unibody a1286 that most likely has a blown fuse.
i'm a mac tech, but don't have any experience soldering boards.
so i'm wondering if folks who have done it successfully would recommend me trying to attempt this repair or not.

thanks!

 

[Dadioh]

greetings,

this is a wonderful thread.
one that also applies to my situation.

i have a unibody a1286 that most likely has a blown fuse.
i'm a mac tech, but don't have any experience soldering boards.
so i'm wondering if folks who have done it successfully would recommend me trying to attempt this repair or not.

thanks!

The fuse is quite small so soldering is best done with magnification and a very fine tip on your soldering iron. If you are not comfortable doing it yourself you might be able to find someone locally who would do it for you. Usually someone who works in electronics manufacturing repair stations.

 

[hyugmyung]

hmmm, off hand, would you know of any in new york city?

i haven't the faintest idea where i would even begin looking.

thanks!

 

[Dadioh]

hmmm, off hand, would you know of any in new york city?

i haven't the faintest idea where i would even begin looking.

thanks!

Maybe an ad on craigslist or kijiji asking for someone with fine soldering skills able to replace an 0402 surface mount fuse.

 

[hyugmyung]

cool thanks, will take the info from this thread and see if i can find someone who will do the right job.

thanks again!

 

[alb404]

Interesting that Apple is using yet a third WLED driver for the Macbook White.

As far as the FAIL indicator, when it says High Impedance that would be in a functioning state. They would have something called a "pull up" resistor on that pin which, when the WLED driver was functioning normally, would pull down the signal to ground potential. If the WLED driver detects a fault it would go into a high impedance mode which would allow the pull up resistor to pull the voltage up to the rail voltage.

In other words, while the board is powered, if you measured 0 Volts on that pin then the WLED device is happy and functioning normally. If you measured rail voltage (depends on what rail the pullup is attached to but let's say 3.3V for arguments sake) then it has detected a fault.

Measure all your pins to ground (with power disconnected) and report back here an I will see if something looks out of sorts.

Hi there.

I've been busy IRL, but I finally had the time to do the measurements here are they:
(as a reminder, I'm working on a White Unibody Macbook)

I hope I got them right, my multimeter's probes are not that thin.

Can you see anything wrong there ?

Thanks a lot for your help

 

[Dadioh]

Hi there.

I've been busy IRL, but I finally had the time to do the measurements here are they:
(as a reminder, I'm working on a White Unibody Macbook)

Image

I hope I got them right, my multimeter's probes are not that thin.

Can you see anything wrong there ?

Thanks a lot for your help

Just to clarify. These are voltage readings with the Macbook started up? Be very very careful if you do not have fine tips on your multimeter probes because it is very easy to short two pins together.

If these are voltages then you have a problem right out of the gate. Vin should not be zero. According to the datasheet it is typical 10V and could be as high as 21V. Given that the Macbook uses 12V everywhere else I am going to guess it should be 12V.

Also VDC1 is supposed to be 2.5V and VDC2 is supposed to be 6.0V.

So it seems you have basic power issues for starters. Vin most likely has a fuse in its input circuit so you need to spot that fuse and test it.

 

[alb404]

Just to clarify. These are voltage readings with the Macbook started up? Be very very careful if you do not have fine tips on your multimeter probes because it is very easy to short two pins together.

If these are voltages then you have a problem right out of the gate. Vin should not be zero. According to the datasheet it is typical 10V and could be as high as 21V. Given that the Macbook uses 12V everywhere else I am going to guess it should be 12V.

Also VDC1 is supposed to be 2.5V and VDC2 is supposed to be 6.0V.

So it seems you have basic power issues for starters. Vin most likely has a fuse in its input circuit so you need to spot that fuse and test it.

My bad, I forgot to mention what I've been measuring. These are not voltage but resistance to the ground, with the motherboard disconnected from anything. I had my multimeter on 2k ohm.

I'm afraid it's not possible to measure voltage, as the chip is on the wrong side of the board.

I apologize for the missing information

 

[Dadioh]

My bad, I forgot to mention what I've been measuring. These are not voltage but resistance to the ground, with the motherboard disconnected from anything. I had my multimeter on 2k ohm.

I'm afraid it's not possible to measure voltage, as the chip is on the wrong side of the board.

I apologize for the missing information

OK. So these are values in kohm. Well Vin should not be zero since that means it is shorted to ground. And GND should be zero. Not sure if yo are hitting the pins right with larger probes.

To verify if the short is internal would require removing the device.

 

[blazie151]

I have an A1342 with a similar issue - no backlight. I checked every fuse on the entire board, and they're all good, but still no backlight. I'm thinking the WLED driver is the culprit, but want to figure out exactly which pins I need to test to verify that the problem is the WLED driver. Also, if this is a blown driver, are there any compatible parts that I can use, or does anyone know where I can buy one?

 

[Papabear60]

Another success for your thread Dadioh

The issue was the 1.2M ohm resistor hanging off pin 9 of the WLED driver.
If it helps the thread I found it interesting that the voltages on the WLED driver pins changed as follows:
Pin: before after
1 0v 3v
2 0v 0.1v
6 0v 0.5v
7 0v 1.3v
9 12v 28v

I was thinking the 0v pins were the issue that was stopping the WLED driver boosting the voltage to 28v but it turns out that was wrong and the WLED driver will output those voltages when all the other inputs are corrected which was interesting and hopefully saves others from wasting a lot of time as I did.

It now works fine except I have to bypass the SMC on start up but I see you have another excellent thread on that issue so I'll read up on that one and "see you on the other side" - Thanks again.

 

[Dadioh]

Another success for your thread Dadioh

The issue was the 1.2M ohm resistor hanging off pin 9 of the WLED driver.
If it helps the thread I found it interesting that the voltages on the WLED driver pins changed as follows:
Pin: before after
1 0v 3v
2 0v 0.1v
6 0v 0.5v
7 0v 1.3v
9 12v 28v

I was thinking the 0v pins were the issue that was stopping the WLED driver boosting the voltage to 28v but it turns out that was wrong and the WLED driver will output those voltages when all the other inputs are corrected which was interesting and hopefully saves others from wasting a lot of time as I did.

It now works fine except I have to bypass the SMC on start up but I see you have another excellent thread on that issue so I'll read up on that one and "see you on the other side" - Thanks again.

Congratulations!

Pin 9 is the feedback to the WLED driver of the voltage it is putting out. It gets the feedback through a 1.2Mohm/71.5Kohm divider network. If your 1.2M resistor was toast then the WLED driver would not be able to read the feedback and would probably shut down. Good job finding that.

----------

I have an A1342 with a similar issue - no backlight. I checked every fuse on the entire board, and they're all good, but still no backlight. I'm thinking the WLED driver is the culprit, but want to figure out exactly which pins I need to test to verify that the problem is the WLED driver. Also, if this is a blown driver, are there any compatible parts that I can use, or does anyone know where I can buy one?

I don't know for certain but I would be surprised if they did not use the same pinout on the LVDS connector as they do on the other 13" models. In that case the backlight voltage is on pins 21 and 22. See if you can find a better place to measure that voltage since you don't want to slip with your probe while you have power on. I usually measure on the cathode of the boost diode if it is on the top.

 

[blazie151]

I don't know for certain but I would be surprised if they did not use the same pinout on the LVDS connector as they do on the other 13" models. In that case the backlight voltage is on pins 21 and 22. See if you can find a better place to measure that voltage since you don't want to slip with your probe while you have power on. I usually measure on the cathode of the boost diode if it is on the top.

In that image I uploaded, is the chip on the right that I'm suspecting to be the WLED driver actually the driver? And what pin on that should I be testing. Would the previously listed pin voltages be the same even if that is a different driver? Luckily, those pads seen around the driver are large enough to get at with a regular probe, so I can measure those much easier. For checking the toes of the LVDS connector I would need much thinner probes.

I just noticed a new symptom now that the board is clean; After disconnecting and reconnecting the battery and powering on the macbook, the screen flickers and then goes black, so it's turning on the LED backlight but only for a fraction of a second.