MacBook Pro Unibody - No Backlight - Logic Board Question

[Dadioh]

Hello Dadioh,
My macbook works good exсept backlight. Reading this thread I can find a backlight fuse (it's dead) and leddriver (looks like working - only 6 pins beeps to ground) but my LCD connector is badly looking (see pics). What could cause this damage? Does anybody seen this before? And if I replace LCD cable and fuse will it work? Sorry for my bad language, I'm from Russia)))

Looks like liquid damage. You should replace the cable but also check the LVDS connector on the logic board. If you look inside the connector with magnification you may see corrosion in there as well. In that case you would need to replace the connector as well.

 

[Juz]

i've got an a1226 (pre-unibody macbook pro with led backlight) with a non-working backlight fault, and would appreciate any help you could offer in pin-pointing the problem.

i don't think it's a graphics problem as i can see the dim picture on screen, and the external display output works fine.

the pins in the connector on the left input/output board which go to the led driver board measure as follows (in red):

i'm not sure if that is as it should be, or if something is wrong there? all i know is that on the older a1181 macbooks with ccfl backlight, the inverter connector has a similar pin layout to this, and i seem to recall also having 3v on one of the pins there which i do not have here?

can anyone advise on where my problem may lie if those figures are as they should be? i'm not sure whether i should be looking at the main logic board, the lio board, or the screen itself.

i'm familiar with ccfl backlights themselves failing, but would an entire led backlight failure be possible, or would it be more likely to just lose one or two of them?

 

[l.a.rossmann]

i've got an a1226 (pre-unibody macbook pro with led backlight) with a non-working backlight fault, and would appreciate any help you could offer in pin-pointing the problem.

i don't think it's a graphics problem as i can see the dim picture on screen, and the external display output works fine.

the pins in the connector on the left input/output board which go to the led driver board measure as follows (in red):
Image

i'm not sure if that is as it should be, or if something is wrong there? all i know is that on the older a1181 macbooks with ccfl backlight, the inverter connector has a similar pin layout to this, and i seem to recall also having 3v on one of the pins there which i do not have here?

can anyone advise on where my problem may lie if those figures are as they should be? i'm not sure whether i should be looking at the main logic board, the lio board, or the screen itself.

i'm familiar with ccfl backlights themselves failing, but would an entire led backlight failure be possible, or would it be more likely to just lose one or two of them?

Is your left I/O board an 820-2273? You can see this number if you remove the wifi card and look through the expresscard slot. Further, if you can take a picture of the bottom of the I/O board, I can show you what you should measure.

 

[Juz]

Is your left I/O board an 820-2273? You can see this number if you remove the wifi card and look through the expresscard slot. Further, if you can take a picture of the bottom of the I/O board, I can show you what you should measure.

i think my LIO is an 820-2102. from what i can gather, this is for the a1226 whereas the 820-2273 is for the a1260 - however they both use LED backlighting with some role in this played by the LIO, so i've taken a photo of the bottom of the board anyway just in case any of it looks similar or recognisable to you?

thankyou

 

[javier castillo]

Im have the same problem, i found out the backlight fuse was not working. Its pretty small. Found this picture on the web that shows the exact fuse.
https://forums.macrumors.com/attachment.php?attachmentid=301342&d=1314998993

i been told to just bridge the fuse but i don't have a good feeling about it. This fuse is pretty small, i want to replace it myself. What tools do i need, for example soldering iron or hot air rework. Im fairly new to soldering and i want to practice before doing such work. Any tip/ help

So i recently replaced the fuse by myself but the backlight still did not turn on. I felt like i did a bad soldering job so i bridged it and still nothing. What can be another cause for the backlight besides the fuse and how can i test it? thankyou

ps. i think it might be the wled driver and if so, where can i buy one

 

[aqibi2000]

Javiour, you stated you assumed you did a bad soldering job, replacement of QPF/SMD items such as the WLED driver requires high quality IR rework equipment or Hot Air although I would not recommend. I would not recommend attempting of your soldering is not pristine.

 

[BacklightFuse]

new fuse

Hello there. I have replaced the blown fuse and now i have backlite but for some reason I dont have a light on the keyboard, any thoughts on where to look or what to replace???

 

[aqibi2000]

Hi everyone, my A1342 backlight is still not working, please somebody help. At my age I really cannot afford to disk out the cost of repair, I own rework equiptment but cannot find the responsible component shorting the WLED driver. The backlight appears to flash on for a 0.000001 second during initial boot but then remains off, the display itself is perfect.

All help would be verily appreciated, and make my family very happy.
Thank you

 

[javier castillo]

Well I ended up about breaking even I would say. Lots of hours to figure out how that circuit worked and then removing and soldering on a QFN package.

http://en.wikipedia.org/wiki/Quad_Flat_No_leads_package

Hey Dadioh, i'm in big problems here. I have no backlight. I replaced both the fuse and wled driver and nothing. A computer repair technician said it might be the LVDS Cable Connector. Do you know how i can replace this part of the logic board?
thank you for all you help, im sure we are all highly appreciative. You rock man

 

[Dadioh]

Hey Dadioh, i'm in big problems here. I have no backlight. I replaced both the fuse and wled driver and nothing. A computer repair technician said it might be the LVDS Cable Connector. Do you know how i can replace this part of the logic board?
thank you for all you help, im sure we are all highly appreciative. You rock man

Depending on whether you have a 13" or 15" the lvds connector is 30 pins and 40 pins respectively. You will need to source a connector. They are made by I-pex. Not too hard to solder with a good iron and microscope. Remove the old one with hot air. Clean the pads. Place the connector. Put a dab of solder at either end to ground and then proceed to solder them one at a time. Then finish by soldering across the width of the ground. Be careful at the two ends not to let the solder on the ground impinge into the inside of the connector or it will interfere with the proper insertion of the connector.

Part number is on the schematic.

 

[BacklightFuse]

no light on keyboard

@dadioh

Could you please help me figure out where to look to get my keyboard light back? Thanks!!

 

[Dadioh]

@dadioh

Could you please help me figure out where to look to get my keyboard light back? Thanks!!

Sure. Which MacBook pro model? On the 13" the backlight connector is beside the keyboard connector. On the 15" it attaches near the fan.

 

[BacklightFuse]

no light on keyboard

Sure. Which MacBook pro model? On the 13" the backlight connector is beside the keyboard connector. On the 15" it attaches near the fan.

@dadioh Hi! Yes I have the connector, but when I power the laptop up the sensor is working, it would let me can play with the - or + from the keyboard to give more or less light intensity to the light underneath the keyboard but no actual light come up from the keyboard. So i'm gessing since the keyboard light works with a diff motherboard and the connector is good, its maybe the chip in the motherboard that is not providing power??? if so wich ic should i check?? the motherboard I'm taking about is a mac pro 15" 820-2533A 2.53ghz

Thanks in advance!

 

[Dadioh]

@dadioh Hi! Yes I have the connector, but when I power the laptop up the sensor is working, it would let me can play with the - or + from the keyboard to give more or less light intensity to the light underneath the keyboard but no actual light come up from the keyboard. So i'm gessing since the keyboard light works with a diff motherboard and the connector is good, its maybe the chip in the motherboard that is not providing power??? if so wich ic should i check?? the motherboard I'm taking about is a mac pro 15" 820-2533A 2.53ghz

Thanks in advance!

There are 4 pins in that connector. Two of them get shorted together when you insert the flex connector and tell the logic board that the backlight is installed and allow it to send the voltage to the keyboard LEDs. Sounds like those pins are OK and the logic board thinks it is connected to the LEDs. The other 2 pins are ground and the 12V (I think that is the voltage) being sent to the LEDs. Check that those pins are OK and making contact with the flex connector. Clean the connector in case it is dirty.

 

[BacklightFuse]

No keyboard backlight yet

There are 4 pins in that connector. Two of them get shorted together when you insert the flex connector and tell the logic board that the backlight is installed and allow it to send the voltage to the keyboard LEDs. Sounds like those pins are OK and the logic board thinks it is connected to the LEDs. The other 2 pins are ground and the 12V (I think that is the voltage) being sent to the LEDs. Check that those pins are OK and making contact with the flex connector. Clean the connector in case it is dirty.

@dadioh. Ok... here are my findinds... After cleaning the connector I attached everything back in place and the left side of the connector, (the shorted pads) is producing around 5volts. Now I tested the same connector on a different board, and when the keyboard light is dim or not present there are 5 volts, full brightness is +18.5volts. So I'm assuming my keyboard circuit is bad or not producing the amount of volts needed for the keyboard to light up. Looking at the schematics there is an IC that controls it and its the LT3491, but I cannot find it on the board.

Could you throw some light to see if I can fix this issue,please?

 

[Dadioh]

@dadioh. Ok... here are my findinds... After cleaning the connector I attached everything back in place and the left side of the connector, (the shorted pads) is producing around 5volts. Now I tested the same connector on a different board, and when the keyboard light is dim or not present there are 5 volts, full brightness is +18.5volts. So I'm assuming my keyboard circuit is bad or not producing the amount of volts needed for the keyboard to light up. Looking at the schematics there is an IC that controls it and its the LT3491, but I cannot find it on the board.

Could you throw some light to see if I can fix this issue,please?

Sounds like you are on the right track. Just to double check that there is not an issue with the keyboard backlight itself dragging the voltage low I would try removing the cable from the connector and then shorting the 2 sense pins together to fool the circuit into thinking a cable is connected. Then measure the DC voltage between the other 2 pins. If it is still 5V then you do have a problem with the LED driver.

I do not know where the particular device is but the datasheet excerpt I have attached below suggests you are looking for a small package, (most likely the DC package knowing Apple) and the markings on the device would either be LCHJ or LBXQ.

 

[destic]

Hi!

I have a Macbook with no backlight, already replaced the LP8543, the fuse is ok. The backlight only flashes for less the 1 sec when manually shutting down the Macbook. I found a voltage drop at the below marked resistor, the resistor itself is ok but the measured voltage before and after it is not the same. Would really appreciate any help!!

 

[Dadioh]

Hi!

I have a Macbook with no backlight, already replaced the LP8543, the fuse is ok. The backlight only flashes for less the 1 sec when manually shutting down the Macbook. I found a voltage drop at the below marked resistor, the resistor itself is ok but the measured voltage before and after it is not the same. Would really appreciate any help!!

Image

That is correct operation. That resistor is part of a divider network 301K / 100K resulting in a drop of the 12V to 3V (the ratio of the resistances) which is the proper level for the enable pin on the WLED driver.

 

[destic]

That is correct operation. That resistor is part of a divider network 301K / 100K resulting in a drop of the 12V to 3V (the ratio of the resistances) which is the proper level for the enable pin on the WLED driver.

Ok thanks very much for the quick reply and sure this looks like a voltage divider on the circuit diagram, I just measured 12v on both sides on another half working board...So this means the led driver I picked up from a dead board is bad...

 

[Dadioh]

Ok thanks very much for the quick reply and sure this looks like a voltage divider on the circuit diagram, I just measured 12v on both sides on another half working board...So this means the led driver I picked up from a dead board is bad...

If you measured 12V both sides then it suggests that the other board has an open circuit 100K resistor or the ground on the 100K resistor is disconnected. The WLED driver enable pin could pull it lower than 3V (possibly) but it could not cause it to stay at 12V.

 

[aqibi2000]

Dadioh please help, my Macbook 2010 has totally stopped powering up, was ex liquid damaged. IPA'ed entire board, still no response. The magsafe shows solid green led but that is it.

Originally I came here for back light advice but now this.

 

[Dadioh]

Dadioh please help, my Macbook 2010 has totally stopped powering up, was ex liquid damaged. IPA'ed entire board, still no response. The magsafe shows solid green led but that is it.

Originally I came here for back light advice but now this.

So no battery charging then if only solid green. What about the white fuse to the right of the memory? Does that have 12V on both sides? If so, have you checked if you have G3HOT?

 

[arakira]

backlight issue on an A1260

Is your left I/O board an 820-2273? You can see this number if you remove the wifi card and look through the expresscard slot. Further, if you can take a picture of the bottom of the I/O board, I can show you what you should measure.

Hello everyone and thanks to all for sharing on this thread !
I actually do have an A1260 with the backlighting problem. My display is fine but completely dim ; I tested with 2 spare LCD and cables, 3 spare LED driver boards, without result. So I am sure the problem comes from either the LIO board (model 820-2273), or the logic board.

I searched for help a few months ago, but there were no experts on this model on the thread at that time... So I hope someone can help me this time

I read the voltages on the output connector of the LIO board, and they are different if the LED driver board is connected or not. If it is disconnected, I read :
PIN 1 : GND
PIN 2 : 12.6v
PIN 3 : 3.3v (should be 5v according to schematics ?)
PIN 4 : from 0v to 3.15v depending on the lightness choosen on keyboard

However, when the LED driver board is unplugged, I read :
PIN 2 : 5v
PIN 3 : 2.4v
PIN 4 : from 0v to 3.15v (identical)

Here are the pictures of the LIO board :

IO board top par arakira, sur Flickr

IO board bottom par arakira, sur Flickr
I took the schematics for the LIO from : http://wenku.baidu.com/view/2c7a076427d3240c8447ef14.html

LIOschematics par arakira, sur Flickr

In case, pictures of the logic board :

logic board top right par arakira, sur Flickr

logic board top left par arakira, sur Flickr

logic board bottom right par arakira, sur Flickr

logic board bottom left par arakira, sur Flickr

If someone could gently show me what component may be faulty (maybe l.a. rossman or wedgeman ?) I would really appreciate.
Many thanks !

 

[l.a.rossmann]

Hello everyone and thanks to all for sharing on this thread !
I actually do have an A1260 with the backlighting problem. My display is fine but completely dim ; I tested with 2 spare LCD and cables, 3 spare LED driver boards, without result. So I am sure the problem comes from either the LIO board (model 820-2273), or the logic board.

I searched for help a few months ago, but there were no experts on this model on the thread at that time... So I hope someone can help me this time

I read the voltages on the output connector of the LIO board, and they are different if the LED driver board is connected or not. If it is disconnected, I read :
PIN 1 : GND
PIN 2 : 12.6v
PIN 3 : 3.3v (should be 5v according to schematics ?)
PIN 4 : from 0v to 3.15v depending on the lightness choosen on keyboard

However, when the LED driver board is unplugged, I read :
PIN 2 : 5v
PIN 3 : 2.4v
PIN 4 : from 0v to 3.15v (identical)

Here are the pictures of the LIO board :
[url=http://farm9.staticflickr.com/8024/7425740504_4303f0aee3.jpg]Image[/url]
IO board top par arakira, sur Flickr
[url=http://farm6.staticflickr.com/5271/7425740844_de364a63aa.jpg]Image[/url]
IO board bottom par arakira, sur Flickr
I took the schematics for the LIO from : http://wenku.baidu.com/view/2c7a076427d3240c8447ef14.html
[url=http://farm8.staticflickr.com/7267/7425741048_45d5666d81.jpg]Image[/url]
LIOschematics par arakira, sur Flickr

In case, pictures of the logic board :
[url=http://farm6.staticflickr.com/5075/7425739718_e9c17f16e4.jpg]Image[/url]
logic board top right par arakira, sur Flickr
[url=http://farm8.staticflickr.com/7137/7425740082_9eab365b83.jpg]Image[/url]
logic board top left par arakira, sur Flickr
[url=http://farm8.staticflickr.com/7255/7425741412_f2606ae025.jpg]Image[/url]
logic board bottom right par arakira, sur Flickr
[url=http://farm9.staticflickr.com/8150/7425741822_fb10f33fca_n.jpg]Image[/url]
logic board bottom left par arakira, sur Flickr

If someone could gently show me what component may be faulty (maybe l.a. rossman or wedgeman ?) I would really appreciate.
Many thanks !

http://www.rossmannsupply.com/blog/?p=32

This should solve your problem!

If that doesn't work, it is a control chip on the logic board that is bad.

How is your soldering experience with surface mount? The package you need to replace first is a 603 package, which is by far the easiest surface mount soldering there is. It can often be done successfully with a simple through hole iron. Although this is not ideal, it is likely the best way to economically perform the job. Reliable, working I/O boards can be had for under $70, which is considerably less than I paid for even my regular through-hole soldering station.

Hope this helps! Don't short it with a wire, it will blow up in your face. I have feared getting involved posting this kind of information for a while out of fear that people unfamiliar with soldering small packages or just too lazy/impatient to order a fuse would put a solder blob over it... I nearly guarantee it will blow up in your face. If not now, later. All it takes is that unlatched connector slipping a tiny bit and wham, it starts smoking with nothing there to stop it.

DON'T SHORT THE FUSE.

 

[arakira]

http://www.rossmannsupply.com/blog/?p=32

This should solve your problem!

If that doesn't work, it is a control chip on the logic board that is bad.

Thank you for your fast reply !
Mmm.. Unfortunately, this fuse is working. Should I test every component in the backlight circuit on the LIO, or test something on the logic board ?

Also, is there a way to determine, given voltages on the cables, if the problem comes from the LIO or logic board ? Just in case, the voltages on the display cable are :
from PIN 2 to PIN 7 : 3.25v
from PIN 8 to PIN 30 : about 1.2v, except PIN 10,13,16,19,22,25,28 : 0v
PIN 31 & 32 : 1.3v
PIN 33 to 36 : 0.8v
PIN 37 : 0v
PIN 38 to 40 : 4.8v

Thanks again !