MacBook Pro Unibody - No Backlight - Logic Board Question

[Dadioh]

Hello! Excellent thread! I have an early-2011 13-inch mbp , of my own, with non working led backlight

The computer is fully functional besides this. (i.e. you can plug an external HDMI device and use it.

The backlight died one day, 1 or 2 minutes after boot. Liquid-damage is discarded.
The days before this happened, there was a very faint flickering in the backlight.



I've taken some measures on the board: (820-2936-A)

There is no damage on LVDS connector, U9701 seems to be OK and there isn't any noticeable rust. I cleaned the board with a new toothbrush just in case.

Fuse F9700 is OK. Voltage reads 11.3V. I get the same reading @ F7040 pin 2.
BKL_EN (on R9731) reads 2,62V
Pins 2&3 of LVDS read 3.25V
Pins 21&22 of LVDS read 11.22V


Can you help me with this? I'd need some advice on the further steps to take. I'll take any measure you ask, provided it's in the top side . In the bottom side I cant measure voltage as i cannot power the board.
I think that WLED driver is OK and something is wrong.

Thank you in advance!

Good detailed info. It looks like you are getting all the right voltages to tell the WLED driver to boost the input 12V to 27V. F9700 is good which feeds 12V through Q9706. You know it is getting through because you have 2.6V at BKL_EN. This is created by the resistor divider network (301K/100K) dividing by 4. The LCD panel is getting it's 3.3V power (pins 2,3). BUT backlight voltage is only the unboosted 11.22V.

So why isn't it boosting?

This can happen if the feedback is not working from cathode of D9701 back to the WLED pin A5 "FB". Because WLED driver is a BGA package it is hard to check continuity there.

It could also be that the WLED driver itself has just failed and requires replacement. You may have to just remove it to check the connections. Assuming you can source a new one however.

 

[phnx2k]

Good detailed info. It looks like you are getting all the right voltages to tell the WLED driver to boost the input 12V to 27V. F9700 is good which feeds 12V through Q9706. You know it is getting through because you have 2.6V at BKL_EN. This is created by the resistor divider network (301K/100K) dividing by 4. The LCD panel is getting it's 3.3V power (pins 2,3). BUT backlight voltage is only the unboosted 11.22V.

So why isn't it boosting?

This can happen if the feedback is not working from cathode of D9701 back to the WLED pin A5 "FB". Because WLED driver is a BGA package it is hard to check continuity there.

It could also be that the WLED driver itself has just failed and requires replacement. You may have to just remove it to check the connections. Assuming you can source a new one however.

Thank You for the answer. I did some more measurements. I've focused on the WLED driver.
First I took resistance measurements on some of the resistors that lie around the driver:

R9715 = 76K (according to schematic this value should be 100K)
R9731 = 100K (according to schematic this value should be 300K)
R9714 = 16K OK!
R9704 = 33 OK!
R9716 = 90K OK!

And then measured some nets to ground:

PPBUS_SW_BKL = 11.16V (measured on C9712 pin 1)
PPBUS_SW_LCDBKLT_PWR_SW = 11.15V
PPVOUT_SW_LCDBKLT_FB = 10.99V
I read the last two values from the pads between the WLED driver and the resistors around it, as shown in the board view. (I downloaded the .brd file for this logic board from this thread)
From these three readings I think the WLED driver is not boosting anything. (My expertise on advanced electronics like this is zero! )

I'd like to measure voltage on some components on the other side of the board but I cannot find the way to do it.

I live in Argentina, a replacement logic board costs more than 1200 u.s. dollars, so it's a no go for anyone here. It was fun to disassemble the macbook, to get into the schematics but I'm giving up on this!

 

[greekhero]

MBP 2009 13" = White screen lcd and external

Hello all,

I have an mbp 2009 that displays white screen on lcd and external display. I have tried different ram, smc and nvram reset but still no luck Never goes to the disk or CD or USB. Does do the bong. charges. Not sure where to look next. Any ideas?

Thanks!

 

[Dadioh]

Hello all,

I have an mbp 2009 that displays white screen on lcd and external display. I have tried different ram, smc and nvram reset but still no luck Never goes to the disk or CD or USB. Does do the bong. charges. Not sure where to look next. Any ideas?

Thanks!

I would see if verbose mode works and tells you at what point it is hanging. After you press power button hold down command key and "v" key. If it works let us know what it displays.

 

[macrepair]

Here you go.

If you are getting backlight but no image then I suspect something in the LVDS signaling or clocks. If the 3.3V supply (pins 2 and 3) is bad then normally the backlight will not come on at all. I believe there is some sort of feedback that is required for the SMC to enable the backlight. Anyway you could check for presence of 3.3V on pins 2 and 3. Be very careful probing with power on. One little slip and short circuits can happen.

Hi Dadioh, thanks for your help with this. Have just tested and there is 0V on pin 2 and 3. The backlight is still coming on without 3.3V present. Have traced this back to component 009F which has 3.3V on opposite side. Could this be the faulty part? Any idea what this part is?

 

[Poeter]

Hello,

I have a MacBook Pro 13-inch model with no wi-fi anymore since customer has put in wi-fi cable wrong in airport. When changing his lcd. I changed the airport but no luck. Is this repairable?

Fuse blown on board near connector i have read on the internet

Regards, Peter

 

[Dadioh]

Hello,

I have a MacBook Pro 13-inch model with no wi-fi anymore since customer has put in wi-fi cable wrong in airport. When changing his lcd. I changed the airport but no luck. Is this repairable?

Fuse blown on board near connector i have read on the internet

Regards, Peter

The blown component is not a fuse. It is a ferrite used for electromagnetic emissions reduction. Grab one off of a spare parts board and replace. There is also another one on the reverse side of the board that may have failed. If it has it should be obvious since they tend to be a fairly traumatic failure mode.

See schematic view below and you will see what a reversal of signals does. 5V wifi power straight to ground with no fuse protecting it (do NOT try this at home kids

 

[greekhero]

Hi Dadioh,

Thanks for your response. It doesn't read the disk at all. I have tried external USB as well to make sure that I can see data transmission light; but no activity at all. Chimes, shows white screen and stays there, I have left it for hours but no luck.

Any ideas?

I would see if verbose mode works and tells you at what point it is hanging. After you press power button hold down command key and "v" key. If it works let us know what it displays.

 

[Dadioh]

Hi Dadioh,

Thanks for your response. It doesn't read the disk at all. I have tried external USB as well to make sure that I can see data transmission light; but no activity at all. Chimes, shows white screen and stays there, I have left it for hours but no luck.

Any ideas?

I am guessing graphics processing unit GPU failure. It is chiming which means all the power rails are ok and memory tested out. But the fact that it won't boot from either sata bus or from USB suggests a fundamental issue. GPU for example.

Unfortunately not much I can suggest to fix it. Possible a solder reflow on the northbridge device which contains the GPU.

 

[tswartfiguer]

I am guessing graphics processing unit GPU failure. It is chiming which means all the power rails are ok and memory tested out. But the fact that it won't boot from either sata bus or from USB suggests a fundamental issue. GPU for example.

Unfortunately not much I can suggest to fix it. Possible a solder reflow on the northbridge device which contains the GPU.

Unfortunately, this is a dead GPU, If you have a rework station buy a new GPU pre-balled and replace. Dadioh is right reflow might work for a few days tops, if you are lucky a bit longer but real solution if replacement here. Or buy another broken board from ebay and use this board as donor board.

Good luck

 

[dieett]

Unfortunately, this is a dead GPU, If you have a rework station buy a new GPU pre-balled and replace. Dadioh is right reflow might work for a few days tops, if you are lucky a bit longer but real solution if replacement here. Or buy another broken board from ebay and use this board as donor board.

Good luck

Hello in the round,
if I may hook here:
my MBP (13 ", 820-2530, mid 2009) backligth not switched on - no video output.
external monitor goes-
Q9807: LVDS_IG _BKL_ON = 0V!
BKLT_L * PLT_RST_L = 3.1 V.
under "Monitors" internal screen but listed!
also a GPU broken?

The experts have their say?

freely translated by google

 

[cpufixer]

mbp late 2009 a1278

Hi guys, I got this mbp 13 inch, no backlight sometimes. I unplugged the battery and that seems to help keep it on, fuses check out good, when power cycling it will stay off, any ideas?


EDIT: ok, guys, took it apart and removed all power, for 30 min, did a few resets, and everything seems to be good now, thanks

 

[Sicilianu]

Hello!i have a big problem!suddenly my macbook pro 15 late 2011 stopped working!i don't have image neither backlight or apple logo light but the system boots perfectly in mavericks.When it was working i ften played counter strike on bootcamp so i am thinking that is the cause for an gpu failure ,but if i connect an external monitor i dont have any image either(i ve done all the existing commands etc. To no avail).what do you think is the problem?it is possible to brake the gpu and the screen also?

 

[Barney63]

Hello!i have a big problem!suddenly my macbook pro 15 late 2011 stopped working!i don't have image neither backlight or apple logo light but the system boots perfectly in mavericks.When it was working i ften played counter strike on bootcamp so i am thinking that is the cause for an gpu failure ,but if i connect an external monitor i dont have any image either(i ve done all the existing commands etc. To no avail).what do you think is the problem?it is possible to brake the gpu and the screen also?

The 15" 2011s were prone to GPU failure (Radeongate).
I'm not sure if this is how it manifests itself.

Barney

 

[Sicilianu]

The 15" 2011s were prone to GPU failure (Radeongate).
I'm not sure if this is how it manifests itself.

Barney

do you think that a reballing will do the trick?

 

[Barney63]

do you think that a reballing will do the trick?

Wait until somebody confirms if that is the symptom of the GPU failure.
Reballing sometimes works but others have also had the GPU replaced at the same time.

Barney

 

[macrepair]

Hi Dadioh, thanks for your help with this. Have just tested and there is 0V on pin 2 and 3. The backlight is still coming on without 3.3V present. Have traced this back to component 009F which has 3.3V on opposite side. Could this be the faulty part? Any idea what this part is?

Just to let you know this was the component at fault. Not sure what the part is but managed to scavenge one off another dead board and all is working correctly now. Thanks again for your help Dadioh!

Was meant to ask, is there somewhere I can download full schematics for MBP?

 

[mAchatronicsEng]

Happy to see this thread active

A special thanks going out to Dadioh for starting AND keeping this tread active.

I have some reading to do to catch up on things in the last year so I will start there before I ask too many questions. I have several MBPs that I will be trying to bring back from the dead in the near future.

Some quick questions:

- Is there a list or repository somewhere for board files and the associated pdf files?

- Has anyone put together a list of resources (both hardware/tools/vendors etc.) that supports the activities listed in this thread? I have some ideas, but didn't want to duplicate effort.

-Are there separate threads for specific HW issues (power supply, intermittent functionality after liquid spill) that focus on the motherboard component level, or has this become all-inclusive thread?

Thanks in advance.

 

[cpufixer]

hi, 15" MBP 2010 a1286 broken screen

hi Guys, I have this 15" MBP with broken screen, Just want to test backlight fuse and can't find one, also it has no hard drive , will the one from my 13" a1278 work? I am waiting for my mini display adapter to see if the mb works, it boots up with sound and lights, but will not turn off when I close the lid, have to press the power button? board is a 820 2533b

 

[mAchatronicsEng]

hi Guys, I have this 15" MBP with broken screen, Just want to test backlight fuse and can't find one, also it has no hard drive , will the one from my 13" a1278 work? I am waiting for my mini display adapter to see if the mb works, it boots up with sound and lights, but will not turn off when I close the lid, have to press the power button? board is a 820 2533b

Yes. The harddrive from a1278 will work. Look up SMC reset and perform as this may fix the issue with not sleeping when the lid is closed. Also check the connector cable between the two screws in you upper right picture to make sure it is connected. This cable is part of the lid switch circuit. I'm as bit confused. You say broken screen. Does this mean it is cracked? You say lights up. Does this mean the small lights in the front showing hard drive activity, battery level leds, or a blank white screen? Also - do you know the damage history of this computer?

 

[cpufixer]

Yes. The harddrive from a1278 will work. Look up SMC reset and perform as this may fix the issue with not sleeping when the lid is closed. Also check the connector cable between the two screws in you upper right picture to make sure it is connected. This cable is part of the lid switch circuit. I'm as bit confused. You say broken screen. Does this mean it is cracked? You say lights up. Does this mean the small lights in the front showing hard drive activity, battery level leds, or a blank white screen? Also - do you know the damage history of this computer?

yes, It looks like the motherboard wants to work, screen is black and cracked, I took the screen apart, so now I need to check if backlight is working before I buy a new screen. I know the fuse is topside....will get to that later, just going to hook up a external screen first...waiting for my wire...


8 Hours LATER: HI guys,, I checked the very small fuse and it looks like it is open. I would need a new solder iron for this, mine is too big, what are you guys using, heat gun maybe? also need a micro scope?

 

[mAchatronicsEng]

yes, It looks like the motherboard wants to work, screen is black and cracked, I took the screen apart, so now I need to check if backlight is working before I buy a new screen. I know the fuse is topside....will get to that later, just going to hook up a external screen first...waiting for my wire...


8 Hours LATER: HI guys,, I checked the very small fuse and it looks like it is open. I would need a new solder iron for this, mine is too big, what are you guys using, heat gun maybe? also need a micro scope?

I have soldered the fuse without use of a microscope, but a cheap jewelers loop may be necessary to inspect the work afterwords. I now use a microscope which is much easier. I have both hot air and solder station and for the fuse solder iron is fine. Buy more than one replacement fuse (easy to loose and you may blow it again).

 

[cpufixer]

this fuse is open, is this digikey part num P15123CT-ND 2 amp 0402 package, thanks to Mac-n-sauce on different post...just checking...

EDIT: so even with this fuse open, the external display should work, is that correct?

 

[mAchatronicsEng]

this fuse is open, is this digikey part num P15123CT-ND 2 amp 0402 package, thanks to Mac-n-sauce on different post...just checking...

EDIT: so even with this fuse open, the external display should work, is that correct?

Yes. If you want to check without an external display, take the computer outside and shine you car's headlamp on the screen. If the graphics are working and it's just the backlight that is not functional, you will be able to see the screen (usually the apple logo on boot).

 

[Dadioh]

Yes. If you want to check without an external display, take the computer outside and shine you car's headlamp on the screen. If the graphics are working and it's just the backlight that is not functional, you will be able to see the screen (usually the apple logo on boot).

Here is a trick I use. I keep a small flashlight at my work bench. Hold it behind the display resting against the apple logo. That lights up a bright circle in the middle of the screen. Then, when booting, if the apple boot logo shows up it is clear as day. Easy to do and avoids the glare from trying to shine a light directly on the screen.