MacBook Pro Unibody - No Backlight - Logic Board Question

[dreds25]

macbook pro A1278/ 2010

hello to everyone dadioh especially ,great thread and some really good info .
Right my problem is with the same logic board as this
https://forums.macrumors.com/attachment.php?attachmentid=286481&d=1306161431
im a bit of a novice with this sort of thing but after reading through alot of this thread i sort of understand the parts to look for and ive tested the 2A fuse and the backlight voltage , both seem to be ok . i have continuity from the 2a fuse and i get reading from the backlight voltage which is leading me to believe its the WLED driver. The trouble im having is that im not sure how to test the QFN package for impedance to ground . if i do need to replace this i am willing to have a go myself (not the worst solderer in the world ) thats where i get lost ?? im not skilled with a mutimeter but i do have one lol can anyone help , ??
Thankyou very much ,
dreds25

 

[denisvelev]

MacBook pro 15" early 2011

Hello!
I have a problem with my mac. The problem is no backlight on Display. This forum helping me to find a solution i changed the "Fuse"
Now I have another problem with display.
The led's on white screen i see.....
See the photo: http://img62.imageshack.us/img62/6098/photoljc.jpg
I have tried on another mac but display is working fine. I think the problem is on motherboard.
Sorry for my English but I am Bulgarian.
Can you help me please?

 

[Dadioh]

Ty dadioh

On the wled driver how can I test if its blown?

Best method is to check resistance between each pin and ground. If it is blown then usually at least 1 pin will show a very different reading than the reference readings.

 

[Dadioh]

Please check the image attached. This is the part I am talking about.

Thanks

That cap probably just provides high frequency smoothing of the voltage so it "might" work without it albeit with some high frequency noise. The pair of 2.2uF caps provide the "grunt" in the circuit to smooth the output of the WLED driver into the LC network. See attachment.

I tried Digikey and Newark and they don't seem to stock any. But here is the search detail so you can see if you can find something in stock.

http://www.digikey.com/scripts/dkse...newproducts=0&ptm=0&fid=0&quantity=0&PV13=119

 

[Dadioh]

hello to everyone dadioh especially ,great thread and some really good info .
Right my problem is with the same logic board as this
https://forums.macrumors.com/attachment.php?attachmentid=286481&d=1306161431
im a bit of a novice with this sort of thing but after reading through alot of this thread i sort of understand the parts to look for and ive tested the 2A fuse and the backlight voltage , both seem to be ok . i have continuity from the 2a fuse and i get reading from the backlight voltage which is leading me to believe its the WLED driver. The trouble im having is that im not sure how to test the QFN package for impedance to ground . if i do need to replace this i am willing to have a go myself (not the worst solderer in the world ) thats where i get lost ?? im not skilled with a mutimeter but i do have one lol can anyone help , ??
Thankyou very much ,
dreds25

To measure impedance (resistance... same thing in this case) between each pin and ground you first disconnect all power (disconnect magsafe and unplug battery). Then place black multimeter lead on ground (any of the screw attachment points on the logic board). Then place the red lead onto each pin and measure the resistance. Most pins you can see what components that they attach to and it is easier to probe at those points. It requires very fine tip leads to probe the connection right on the QFN package. I posted a link to the lead set that I use earlier in the thread.

Replacing the QFN package will require a hot air tool as well as a fine tip soldering iron. Also a microscope unless you have eagle eyes. There are some guides online but they tend to make it look a lot easier than it is to solder a QFN package. If you have never done it before I suggest you seek professional help... the soldering kind that is

----------

Hello!
I have a problem with my mac. The problem is no backlight on Display. This forum helping me to find a solution i changed the "Fuse"
Now I have another problem with display.
The led's on white screen i see.....
See the photo: http://img62.imageshack.us/img62/6098/photoljc.jpg
I have tried on another mac but display is working fine. I think the problem is on motherboard.
Sorry for my English but I am Bulgarian.
Can you help me please?

The pattern at the bottom is because not all LED's are lighting up. This is usually a sign of a bad connection in the LVDS connector or 1 or more of the LED return lines is bad. Check the zero ohm resistors on the LED return leads to make sure they are not open circuit.

 

[denisvelev]

MacBook pro 15" early 2011

Solve this problem, thanks to you! As the connector is pushed straightened. So I underwent sub connector piece (nylon) which is exactly like it.

 

[dreds25]

To measure impedance (resistance... same thing in this case) between each pin and ground you first disconnect all power (disconnect magsafe and unplug battery). Then place black multimeter lead on ground (any of the screw attachment points on the logic board). Then place the red lead onto each pin and measure the resistance. Most pins you can see what components that they attach to and it is easier to probe at those points. It requires very fine tip leads to probe the connection right on the QFN package. I posted a link to the lead set that I use earlier in the thread.

Replacing the QFN package will require a hot air tool as well as a fine tip soldering iron. Also a microscope unless you have eagle eyes. There are some guides online but they tend to make it look a lot easier than it is to solder a QFN package. If you have never done it before I suggest you seek professional help... the soldering kind that is

----------

thanks dadioh , i actually managed to work out how to measure the WLED driver pins . and pin 4 is 3 v is that right ? now i'm thinking it may be the screen as the previous owner dropped it , but i cannot test untill i get a mini dvi to vga lead ..
Also i have this problem on another macbook and it is not the screen as i have switched it with another working screen on a macbook pro , here's a pic

 

[dreds25]

mbp

also on the QFN package i get roughly the same readin from all pins except one which is on the top row in the pic 3rd in from the right , the multimeter just beeps when grounded ? is that right or not ?
Thanks for any help on these matter s .. i really appreciate it
ps sorry for the fuzzy pic lol, need a better camera

 

[Musicsoul78]

Best method is to check resistance between each pin and ground. If it is blown then usually at least 1 pin will show a very different reading than the reference readings.

Ty thanks dadioh
Wled is good then
Must be one of the surrounding fuses.
I'm on it

 

[symuncez]

Macbook Pro Mid-2009 2.53 GHZ (Single Fan Model)

'Sup Folks,

First off, AWESOME THREAD! And righteous salute to Dadioh primarily, and all tech savvy DIY'ers.


After reading this entire thread (. . . and boy there's a lot of coverage here) I replaced my fuse. Followed instructions to the letter.


Here's my problem: After booting up my screen illuminated, then a second later POOF . . . SMOKE and the machine shut off.

I immediately disconnected all power, and removed my entire display. Then replugged it, and it booted up quietly as normal. I inspected the board with a magnifier and can see no sign as to where the smoke came from. No obvius burn marks. . . The fuse did blow, and no longer has continuity.



So here's my question: Can someone point me to the resistor that is in circuit with this fuse. I'd appreciate any assistance to diagnosing the issue before I replace another fuse.



I know there's a schematic somewhere in this 40+ page thread (which I'll be looking for in the meanwhile), but if ANYONE has any helpful short cuts that can help me save time, please help. THANKS in advance.



Btw, I have both a brand new LCD screen and new LVDS cable


- symuncez

 

[symuncez]

Macbook Pro Mid-2009 2.53 GHZ (Single Fan Model), Blown WLED??

To measure impedance (resistance... same thing in this case) between each pin and ground you first disconnect all power (disconnect magsafe and unplug battery). Then place black multimeter lead on ground (any of the screw attachment points on the logic board). Then place the red lead onto each pin and measure the resistance.
Replacing the QFN package will require a hot air tool as well as a fine tip soldering iron. Also a microscope unless you have eagle eyes. There are some guides online but they tend to make it look a lot easier than it is to solder a QFN package. If you have never done it before I suggest you seek professional help... the soldering kind that is

----------

Dadioh,

If you have a moment to spare, I'm wondering if the WLED Driver for my MBP is the same as the one you referenced earlier in this thread. It's not clear to me if the LP8543 can be substituted for what I have L8543SQ.


Also, I'm also looking for help in identifying the resistance for my WLED driver, to determine if it's blown or part of the problem. Simply not sure whether the values you've listed for the LP8543 are relevant to the WLED driver I have.

Any help in interrogating my WLED driver is much appreciated.

 

[NicoNL]

White Macbook 13 inch Core Duo

GPU are the main cause of kernel panics in most macs...
Remove the heat sink
Apply flux to the GPU and reflow that area
Search video on reflow
Then check if it still panics

----------

Thanx for answering.

I repaired lots of windows laptops, very often it is the GPU, but then it is actually almost always a NVIDIA (or sometimes ATI), never an Intel. With some HP's (NC6120) it is the Intel southchip...

Anyways, in the meantime I reflowed the south-chip (82801), northchip/GPU and the microprocessor itself. To no avail...

3 peculiar things:
- when I try to reset the NV RAM (cmd alt P R), the LCD is switching off, but the machine is not really resetting and the white led in front is switching on. I have to press the power button for several seconds to switch (really) off and then switch on again
- the lcd flashes brief (1/10 of a second) at the same moment I press the power button, then after a second the normal start up sequense starts (till the "You need to restart" message)
- when I keep pressing the power button instead of releasing it, after 5 seconds the white led is going to blink fast, then steady, then a 3 second beep and then it is powering up normally (till the "You need..." message)

I think I need the original install DVD for a diagnostic test?
Or does anyone have any idea what causes this kernel panic??

 

[Dadioh]

Dadioh,

If you have a moment to spare, I'm wondering if the WLED Driver for my MBP is the same as the one you referenced earlier in this thread. It's not clear to me if the LP8543 can be substituted for what I have L8543SQ.


Also, I'm also looking for help in identifying the resistance for my WLED driver, to determine if it's blown or part of the problem. Simply not sure whether the values you've listed for the LP8543 are relevant to the WLED driver I have.

Any help in interrogating my WLED driver is much appreciated.

When I look on Digikey I only see LP8543. Can't find an L8543. Is that the marking on top of your device?

Anyway, I would say that the same LP8543 device is used on all the 2009 Macbooks. 2010 models went to LP8545 which is not compatible to LP8543.

 

[dreds25]

mbp

hi all again , anyone got any ideas about my problems above ?
thanks folks
(trying hard lol)

 

[Musicsoul78]

Thanx for answering.

I repaired lots of windows laptops, very often it is the GPU, but then it is actually almost always a NVIDIA (or sometimes ATI), never an Intel. With some HP's (NC6120) it is the Intel southchip...

Anyways, in the meantime I reflowed the south-chip (82801), northchip/GPU and the microprocessor itself. To no avail...

3 peculiar things:
- when I try to reset the NV RAM (cmd alt P R), the LCD is switching off, but the machine is not really resetting and the white led in front is switching on. I have to press the power button for several seconds to switch (really) off and then switch on again
- the lcd flashes brief (1/10 of a second) at the same moment I press the power button, then after a second the normal start up sequense starts (till the "You need to restart" message)
- when I keep pressing the power button instead of releasing it, after 5 seconds the white led is going to blink fast, then steady, then a 3 second beep and then it is powering up normally (till the "You need..." message)

I think I need the original install DVD for a diagnostic test?
Or does anyone have any idea what causes this kernel panic??

have you tried removing all cables apart from trackpad and keyboard???
use external display see if it panics,,
then slowly add devices to see if something else is the cause???

----------

repairing my mbp13 2011

and when i turn on all i get is contsant beep then pause then beep again ... any one know the cause of this error???

i check board for shorts, swapped out ram.and limited devices...

any ideas will be great!

example it goes beep pause beep pause beep pause beep ... forever!

update
just removed the backlight fuse and it booted up again

so replaced the backilight fuse same thing happened

dadioh is this the cause of the wled driver???

 

[Liberatingpulse]

My Macbook Pro 13 inch mid-2009 is not charging. It was working right up until the battery died, at which point, I could not use it because it had stopped charging.

A little background. - This is a macbook that survived a car crash. The case was mangled, but the logic board worked once I removed it. I took the working logic board and put it into the case of a 2011 model macbook pro that had been completely destroyed by Ramen (like, half of the components were either disconnected or vaporized - no chance of saving it).

Anyway, I managed to mess up the backlight while putting it together. I tried to replace the fuse following this thread, but that didn't fix my problem, so I decided to ignore it and use an external monitor. It was working fine for a month before it stopped charging. The light was dim before when it was charging, but now, there's nothing. No lights, no power.

I then took the compter apart to examine what could be wrong and I noticed that a part had desoldered itself from the board. I believe the reason this happened was because one of the screw posts from the unibody frame was shorting the part. In fact, I'm sure of this. I then removed the offending post, cleaned off the board and the part and re-soldered it. I was hoping this would fix the problem, but it hasn't. I measured the resistance of this part and it's identical neighbor and they both read ~1 M Ohm. [edit: just discovered that these are diodes... no wonder the high readout!] Here's a picture of the parts in question.

I'm still getting 16 volts off the magsafe connector module, so I don't think there's anything wrong there.
[edit: checked both main fuses (the one by the battery and the one by the magsafe connector) and they're both fine]

I've seen a lot of success around here and I'd like to thank Dadioh for keeping this thread alive and offering his advice for all these years. Anyway, if you have any idea of how I can fix this, that would be great!

 

[gb123]

Odd indeed. Either the backlight circuit or the SMC seems to be flakey. My guess is the SMC based on the odd influences of battery and magsafe.

Hey, thanks for replying and sorry for dragging this back up after not replying (apparently I don't understand how thread subscriptions work).

Where do you suggest I go from here? How can I narrow down the issue? You mention the SMC, but how can I confirm that, and what can I do about it if/when I do?

FWIW, after living with this for a few weeks, I can no longer get it to boot with the backlight at all and have resorted to using an external monitor (not ideal for several reasons).

 

[symuncez]

When I look on Digikey I only see LP8543. Can't find an L8543. Is that the marking on top of your device?

Anyway, I would say that the same LP8543 device is used on all the 2009 Macbooks. 2010 models went to LP8545 which is not compatible to LP8543.

Thanks for responding . . .

I have ordered several LP8543 devices and I have 3 remaining spare fuses.

Since the fuse blew in the manner that it did, I can only conclude that there's a failed resistor or resistors in circuit with the driver.

Since I don't have a schematic, and don't want to risk another blow, can you share with me the essential components related to the backlight?


My soldering skills are fine. However, I am wondering if the blown fuse could have been caused by some infinitesimal amount of flux that (unseen) remained after clean up.

-OR-


If there're are resistors or other related components could be the cause for the fault.


I certainly welcome all help to troubleshoot this issue. Thanks.


-symuncez

 

[Dadioh]

My Macbook Pro 13 inch mid-2009 is not charging. It was working right up until the battery died, at which point, I could not use it because it had stopped charging.

A little background. - This is a macbook that survived a car crash. The case was mangled, but the logic board worked once I removed it. I took the working logic board and put it into the case of a 2011 model macbook pro that had been completely destroyed by Ramen (like, half of the components were either disconnected or vaporized - no chance of saving it).

Anyway, I managed to mess up the backlight while putting it together. I tried to replace the fuse following this thread, but that didn't fix my problem, so I decided to ignore it and use an external monitor. It was working fine for a month before it stopped charging. The light was dim before when it was charging, but now, there's nothing. No lights, no power.

I then took the compter apart to examine what could be wrong and I noticed that a part had desoldered itself from the board. I believe the reason this happened was because one of the screw posts from the unibody frame was shorting the part. In fact, I'm sure of this. I then removed the offending post, cleaned off the board and the part and re-soldered it. I was hoping this would fix the problem, but it hasn't. I measured the resistance of this part and it's identical neighbor and they both read ~1 M Ohm. [edit: just discovered that these are diodes... no wonder the high readout!] Here's a picture of the parts in question.

Image

I'm still getting 16 volts off the magsafe connector module, so I don't think there's anything wrong there.
[edit: checked both main fuses (the one by the battery and the one by the magsafe connector) and they're both fine]

I've seen a lot of success around here and I'd like to thank Dadioh for keeping this thread alive and offering his advice for all these years. Anyway, if you have any idea of how I can fix this, that would be great!

Those are actually the pair of 2.2uF caps for the WLED driver. See attachment for the pair of caps next to the highlighted 200pF cap. So if one of those was shorted to ground on the backlight voltage side then it would probably blow the backlight fuse. You should be measuring 1Mohm plus since they are Caps.

But that should not be related to a non-charging issue. These caps affect backlight only.

You may be getting 16V on the Magsafe entry point but it is also essential that the centre sense pin be 3.4V. If it is 0V then there is something wrong in the charge circuit or in the components that feed that sense line. That sense line is a serial data connection between the SMC and the Magsafe so it is not about having 3.4V DC. That is just an indication that it is working so don't get any ideas about shorting it to 3.4V

I have another thread about SMC bypass in which there is more info on troubleshooting charging circuit. You might want to hop over there and see if you can get some ideas. Cmdrdata and some others are also making awesome contributions in that thread.

Good luck

 

[Dadioh]

Thanks for responding . . .

I have ordered several LP8543 devices and I have 3 remaining spare fuses.

Since the fuse blew in the manner that it did, I can only conclude that there's a failed resistor or resistors in circuit with the driver.

Since I don't have a schematic, and don't want to risk another blow, can you share with me the essential components related to the backlight?


My soldering skills are fine. However, I am wondering if the blown fuse could have been caused by some infinitesimal amount of flux that (unseen) remained after clean up.

-OR-


If there're are resistors or other related components could be the cause for the fault.


I certainly welcome all help to troubleshoot this issue. Thanks.


-symuncez

Here are some tips on the backlight circuit for the MBP13 2009 model with LP8543 WLED driver. Principles will be similar for other models. Hopefully this helps you search for what is required.

 

[symuncez]

Here are some tips on the backlight circuit for the MBP13 2009 model with LP8543 WLED driver. Principles will be similar for other models. Hopefully this helps you search for what is required. I will see about marking up a logic board picture with the component locations.

THANKS (again )

Just so you know, I followed your procedure for fuse replacement to the letter. I wasn't expecting a fault. The smoke was quite a surprise.

Since the fuse was obviously new, the fault must be elsewhere in the circuit. Once isolated, I'll be well on my way.

Btw, I don't see a pm feature in my account, but as a debt of gratitude for this thread I'd certainly be willing to paypal you funds for a couple of good six packs as a small token.

-symuncez

 

[Dadioh]

THANKS (again )

Just so you know, I followed your procedure for fuse replacement to the letter. I wasn't expecting a fault. The smoke was quite a surprise.

Since the fuse was obviously new, the fault must be elsewhere in the circuit. Once isolated, I'll be well on my way.

Btw, I don't see a pm feature in my account, but as a debt of gratitude for this thread I'd certainly be willing to paypal you funds for a couple of good six packs as a small token.

-symuncez

Fuses are supposed to prevent the smoke

I would start by measuring the 2 backlight pins on the LVDS connector. With power off, battery disconnected, check the resistance between those pins and ground (any screw point). If it is low resistance then that may be the issue. Likely a bent pin inside the LVDS connector. If you can peer into the end of the connector with the cable removed you may see if the pins are straight. I hold it on edge under my microscope.

 

[Dadioh]

Hey, thanks for replying and sorry for dragging this back up after not replying (apparently I don't understand how thread subscriptions work).

Where do you suggest I go from here? How can I narrow down the issue? You mention the SMC, but how can I confirm that, and what can I do about it if/when I do?

FWIW, after living with this for a few weeks, I can no longer get it to boot with the backlight at all and have resorted to using an external monitor (not ideal for several reasons).

Do you have the install DVD for apps that came with the MacBook? That has Apple Hardware Test on it. With DVD in drive hold down the D key while booting and it should start AHT. Run that and see what fails. Might give a better idea.

 

[symuncez]

Fuses are supposed to prevent the smoke

I would start by measuring the 2 backlight pins on the LVDS connector. With power off, battery disconnected, check the resistance between those pins and ground (any screw point). If it is low resistance then that may be the issue. Likely a bent pin inside the LVDS connector. If you can peer into the end of the connector with the cable removed you may see if the pins are straight. I hold it on edge under my microscope.

Ooooo-Kaaaaaaayyyyy,

Dadioh . . . your forensic skills are laudable!! I went back to look at the LVDS Connector with a microscope. And, something STRANGE seems to be attached to it that escaped my notice. I decided NOT to remove it, and get your thoughts first. . . (Online, the replacement connectors don't appear to have this odd element on it). This MIGHT be the cause, not sure.

It appears obvious, but I'd like to be certain. (See Image 2)


UPDATE EDIT: The grey glob on pins 1 and 2 is solder paste. It was semi-solid and a little tough to remove. Anyhow after removing the solder paste glob, the vertical pin of #1 seems to be bent and possibly fused to the vertical pin of #2. I got this unit 2nd hand, and it appears the 1st owner MAY have tried his hand at a fix before selling on ebay.

Good looking out. I never would have looked at the connector. Hopefully it didn't cause any subsequent damage.


Question: Would solder paste bridging pins 1 and 2 cause the display to short out and blow the fuse?

-symuncez

Image 1 = Logic Board . . .

Image 2 = LVDS Connector

Image 3 = Backlight Component Area

 

[zixu]

MBP 15" - i7. Logic board 820-2915-A

Hello Guys, thank you for this magnificent thread. It helps a lot.


I`m dealing with MBP 15" - i7. Logic board 820-2915-A.

After trying LED replacement it came with NO Backlight & No Image on the screen. But it works on External Screen.

I checked the FUSES all are OK.
I replaced the LP8550 WLED Driver (Big pain until I manage to replace this BGA chip ) but still no backlight and matrix is not turning on.

I made some measurements. And it looks like Wled Driver is not getting ENable voltage,
Enable voltage is controlled by PPBUS_SW_BKL=PPBUS_SW_LCDBKLT_PWR, I don`t have any voltage on that line.

Also R9731=300k and R9715=100k are OK.

When I look that line is giving power to the WLED Driver and LED Display after boost diode.

This 12V rail is controlled by Q9706 P-MOSFET which should be open with 0V on its gate. R9788 is holding it CLOSED with continuous 12V.



On other side Q9707 is with 2 x N-MOSFETS which are closed all the time and waits LCD_BKLT_EN & BKLT_PLT_RST_L signal to turn then ON so they can open Q9706 and give the 12V to PPBUS_SW_BKL

LCD_BKLT_EN - signal should come from U9600 which is mystery for me what this chip does. And how it can be related to BKLT Enable.

Does anyone have idea what can be causing this MOSFETS to DO Not turn ON. And how it can be such mess after LED replacement. I had burned fuses before but such a mess like this is hitting me for first time.

I`m attaching the Schematic if you want to digg in.

I`m out of ideas guys, please advice.

G.