I can't find a data sheet searching the numbers on the top of that device. Can you check the back of the logic board and see if there is another device in a similar QFN package near that area?
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MacBook Pro Unibody - No Backlight - Logic Board Question
- Thread starter Dadioh
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I can't find a data sheet searching the numbers on the top of that device. Can you check the back of the logic board and see if there is another device in a similar QFN package near that area?
Hi this is a great thread hope you will be able to help me. I have posted in the past with an issue i have with me MBP 2.3 I5, it has had liquid damage and I have cleaned the board with 99.9% alcohol as you instructed and I replaced the LCD screen as it was faulty every thing works but what I have now across the bottom of the screen is light and dark spots as if only part of the bottom backlights are working I had the same issue before i changed the lcd and I know that the cable is 100% perfect
I have seen this happen when the lvds cable was not properly seated and the retaining clip properly secured. Ultimately it is one of the 6 backlight return signals not working. You could check the 6 resistors on the return lines to see if one of them is open circuit.
They are on pins 24 to 29 of the LVDS connector. On the non-Pro Aluminum unibody they are zero ohm resistors. On the Pro 13" they are 10.2ohm resistors. Not sure what value they would be on for model. Just make sure they are all the same.
The resistors should all be grouped nearby somewhere near the LVDS connector and the WLED driver. Start searching from one of the LVDS pins.
Macbook Spillage
Dadioh,
I have been looking for a forum like this for quite some time and was delighted when I saw a 'close to' match. I'm in college going to be a mechanical engineer, so currently I'm taking electronics, though as you know, that still means I know little to nothing about how my laptop works. But with that said, I have access to multi-meters and some possible guidance from professors. I have a 2.4 GHz A1278 from Mid-2010. It has a backlight issue where it randomly dims, sometimes sparatically almost as if its oscillating or having a seizure. (When I was gone out of the room, a roommate of mine accidentally knocked over a cup of water onto it.) Like therat69, my display has dark and light spots across the bottom which are more apparent if I dim the screen any, and show up more when the backlight randomly dims. So I'm graced with a backlight, well, most of the time at least... though it's good I'm not epileptic.
So basically I was wondering what your ideas are about what it could be? I don't think it can be a burnt fuse since obviously it works part of the time. It possibly could be the LVDS cable where it connects to the logic board? When I went to get help from the technician at the apple store, he just gave me a weird look and asked me if I had spilt a liquid on it lately. Then told me to send it in... Basically, I'm just looking for an alternative to a $750 repair... if there is anyway to make that happen.
This is what I meant about the dark and light spots.
Dadioh,
I have been looking for a forum like this for quite some time and was delighted when I saw a 'close to' match. I'm in college going to be a mechanical engineer, so currently I'm taking electronics, though as you know, that still means I know little to nothing about how my laptop works. But with that said, I have access to multi-meters and some possible guidance from professors. I have a 2.4 GHz A1278 from Mid-2010. It has a backlight issue where it randomly dims, sometimes sparatically almost as if its oscillating or having a seizure. (When I was gone out of the room, a roommate of mine accidentally knocked over a cup of water onto it.) Like therat69, my display has dark and light spots across the bottom which are more apparent if I dim the screen any, and show up more when the backlight randomly dims. So I'm graced with a backlight, well, most of the time at least... though it's good I'm not epileptic.
So basically I was wondering what your ideas are about what it could be? I don't think it can be a burnt fuse since obviously it works part of the time. It possibly could be the LVDS cable where it connects to the logic board? When I went to get help from the technician at the apple store, he just gave me a weird look and asked me if I had spilt a liquid on it lately. Then told me to send it in... Basically, I'm just looking for an alternative to a $750 repair... if there is anyway to make that happen.
This is what I meant about the dark and light spots.
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Dadioh,
I have been looking for a forum like this for quite some time and was delighted when I saw a 'close to' match. I'm in college going to be a mechanical engineer, so currently I'm taking electronics, though as you know, that still means I know little to nothing about how my laptop works. But with that said, I have access to multi-meters and some possible guidance from professors. I have a 2.4 GHz A1278 from Mid-2010. It has a backlight issue where it randomly dims, sometimes sparatically almost as if its oscillating or having a seizure. (When I was gone out of the room, a roommate of mine accidentally knocked over a cup of water onto it.) Like therat69, my display has dark and light spots across the bottom which are more apparent if I dim the screen any, and show up more when the backlight randomly dims. So I'm graced with a backlight, well, most of the time at least... though it's good I'm not epileptic.
So basically I was wondering what your ideas are about what it could be? I don't think it can be a burnt fuse since obviously it works part of the time. It possibly could be the LVDS cable where it connects to the logic board? When I went to get help from the technician at the apple store, he just gave me a weird look and asked me if I had spilt a liquid on it lately. Then told me to send it in... Basically, I'm just looking for an alternative to a $750 repair... if there is anyway to make that happen.
This is what I meant about the dark and light spots.
Image
Welcome to the thread and good luck with your studies. I am an electrical engineer but I work with a lot of mechanical engineers in my field so I probably know about as much about mechanical as you know about electrical
You are correct. It can't be the fuse since that is a one way street. Once they blow there is no intermittency allowed.
As far as the pattern of light you are seeing at the bottom of the screen, this is caused by not all of the LED strings being powered. Although there are 2 or 3 pins that take power through the LVDS connector, there are at least 6 pins returning the current to the WLED driver. It looks like one of those is not working on yours. This can definitely be a poor connection on the LVDS connector itself or, possibly, an issue with the trace or resistor between the connector and the WLED driver. Near the WLED driver you will see a group of 6 (maybe more, I don't have one of your models to check) 0402 size resistors (probably black). If you can tell me the readings on top of the WLED driver I can tell you which pins they attach to and you can measure them for an open circuit. On some models they are zero ohm resistors and on others they are about 10 ohms.
As far as intermittency in the backlight (flickering) that also sounds like a bad connection in the LVDS connector. Remove the battery and then carefully unlatch the LVDS clip and pull the LVDS cable and examine the connection. Look at the gold contacts on the LVDS cable itself as well as the condition of the connector on the logic board. If you've access to a microscope that would make it a lot easier.
Good luck.
Great thread and amazing dedication Dadioh.
I have the same flickering backlight as mention before on a mid 2001 MBP A1278.
Fuse is ok and I've got 12V on both sides. When I started troubleshooting I could get about 25V out of the boost diod and I had 3V on pin 4 on my LED driver (it's a LP8545) but it was dropping slowly. If I turned down my backlight and then back up again it would sometimes go up to 27V on the diod and work for a short instance and then go black again. Tension would then drop slowly and if I turned down backlight completely it would stop at around 12-13V.
Now I it seems to change all the time between 0.3V and 12V. I still have 12V on both side of the fuse. I disconnected the battery and checked the resistance of the two used as the voltage divider (I guess) and they were around 180k and the other 100k which is not the 300k that has been specified before but I should (if I calculated correctly) give me more than 3V. Strange thing is that I don't get 12V on either side of the resistors. Are the 12V coming straight from the fuse to the resistors?
Any suggestions on where I can go from here would be greatly appreciated.
I have the same flickering backlight as mention before on a mid 2001 MBP A1278.
Fuse is ok and I've got 12V on both sides. When I started troubleshooting I could get about 25V out of the boost diod and I had 3V on pin 4 on my LED driver (it's a LP8545) but it was dropping slowly. If I turned down my backlight and then back up again it would sometimes go up to 27V on the diod and work for a short instance and then go black again. Tension would then drop slowly and if I turned down backlight completely it would stop at around 12-13V.
Now I it seems to change all the time between 0.3V and 12V. I still have 12V on both side of the fuse. I disconnected the battery and checked the resistance of the two used as the voltage divider (I guess) and they were around 180k and the other 100k which is not the 300k that has been specified before but I should (if I calculated correctly) give me more than 3V. Strange thing is that I don't get 12V on either side of the resistors. Are the 12V coming straight from the fuse to the resistors?
Any suggestions on where I can go from here would be greatly appreciated.
I think you are describing resistors that are feeding the enable pin? Don't have access to a schematic right now. If so, the enable comes from another circuit (maybe the SMC). It sounds like what you are describing is the WLED driver measuring its output and then becoming unhappy with the result and backing off the voltage.
Which year is yours? Pretty sure it isn't 2001 unless you have a time machine ;-)
hi folks.
simply, this thread is amazing.
anyway, down to business. I am actually in need of a little help myself. I have a MacBook 2009 A1342, (the white Polycarbonate unibody version) where currently the backlight is not working. You can see the screen working though if i shine a touch up against it. Works fine with a external moniter to. I have tried all the resets, but nothing worked.
Anyway i have pulled it apart and ran a few tests.
The fuse, has no continuity.
The 6 resisters that are hang on LED return lines all read 10.8ohms.
WLED Driver resistance to ground.
If anyone can please, please shed any light on anything that looks out of the ordinary, i would surely appreciate it. If you need anything more as well, ala measurements or pictures, let me know.
Cheers
simply, this thread is amazing.
anyway, down to business. I am actually in need of a little help myself. I have a MacBook 2009 A1342, (the white Polycarbonate unibody version) where currently the backlight is not working. You can see the screen working though if i shine a touch up against it. Works fine with a external moniter to. I have tried all the resets, but nothing worked.
Anyway i have pulled it apart and ran a few tests.
The fuse, has no continuity.
The 6 resisters that are hang on LED return lines all read 10.8ohms.
WLED Driver resistance to ground.
If anyone can please, please shed any light on anything that looks out of the ordinary, i would surely appreciate it. If you need anything more as well, ala measurements or pictures, let me know.
Cheers
Dadioh,
I have been looking for a forum like this for quite some time and was delighted when I saw a 'close to' match. I'm in college going to be a mechanical engineer, so currently I'm taking electronics, though as you know, that still means I know little to nothing about how my laptop works. But with that said, I have access to multi-meters and some possible guidance from professors. I have a 2.4 GHz A1278 from Mid-2010. It has a backlight issue where it randomly dims, sometimes sparatically almost as if its oscillating or having a seizure. (When I was gone out of the room, a roommate of mine accidentally knocked over a cup of water onto it.) Like therat69, my display has dark and light spots across the bottom which are more apparent if I dim the screen any, and show up more when the backlight randomly dims. So I'm graced with a backlight, well, most of the time at least... though it's good I'm not epileptic.
So basically I was wondering what your ideas are about what it could be? I don't think it can be a burnt fuse since obviously it works part of the time. It possibly could be the LVDS cable where it connects to the logic board? When I went to get help from the technician at the apple store, he just gave me a weird look and asked me if I had spilt a liquid on it lately. Then told me to send it in... Basically, I'm just looking for an alternative to a $750 repair... if there is anyway to make that happen.
This is what I meant about the dark and light spots.
Image
That is most often an LCD issue, not a board issue.
On this model, a bad connection will not result in a flickering LCD. A flickering LCD as it moves is the LCD. If you see no image in addition to no backlight, or backlight with no image, then it is the cable.
So, to summarize,
a) No backlight
97% chance WLED driver related issue
3% chance LCD related issue
b) No backlight AND no image:
97% chance bad LCD
3% chance bad cable
c) Backlight, but no image
99.99% chance bad LVDS cable
0.01% chance bad LCD
d) Image and backlight work, but it flickers, or sections of the LCD look like a scrambling TV
99.9999999% chance LCD
0.0000001% chance cable
I'm not basing this on specific scientific research. I'm basing it on about 3 and a half years of working on these machines daily and observing & recording what was wrong when we had a particular issue. I hope this helps some people.
This thread has been incredibly informative thus far. I really appreciate when information like this is openly shared, opposed to being seen as a "trade secret", this is what the internet is all about.
I hope this helps.
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Are those resistance measurements in ohms or kohms?
Either way some of them look like they are zero when they should not be. For example pins 19 and 21 are ground but you measure something other than zero ohms to them. Is it possible your probe tips are a bit large and not hitting the actual pins?
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Good summary. Something else I can add. I have, on 2 occasions had an issue with metal getting jammed inside the LVDS connector upon reattaching the LVDS cable. Looking at it under a microscope it appear that what has happened is that as the LVDS cable is inserted it peels up one of the bottom ground contacts and pushes it into the LVDS pins at the back of the connector. In both cases I ended up replacing the LVDS connector. In one of those cases... problem resolved. In the other case it seems to have damaged something in the display circuitry on the logic board. I am turning that one into a displayless media centre for my daughter
Hello componentfix and all other members,
I have also a 15" Pro 2,4ghz 2009 with not working lcd backlight.
I can not find the F9800 you're talking about, i have two boards here, 1 good (although backlight) and 1 test board. If i make a picture can someone tell me what part i need to measure with mulitmeter and how?
Regards, new member Peter
Does that board have an SD memory card slot or is it the late 2008 unibody without the SD slot?
If it has the SD slot then the fuse is located on the back of the logic board nearest the LVDS connector and along the edge of the fan cutout. Post a closeup of that area and I will point it out to you.
I don't have any of those to look at. Can you post high res pictures of the front and back of the logic board near the LVDS connector? I should be able to spot it as long as the resolution is good enough.
lvds cable
i have a late 2008 15" unibody with the no backlights. the motherboard has not been liquid damaged. initially on opening the machine i noticed the lvds connector on the motherboard was burnt, it looks like the metal clip that secures the connector had shorted the last few pins on the left side of the connector. i cleaned up the burnt area and insulated the clip, took the motherboard out and found the blown fuse, i decided to bridge the fuse, but the lights still didn't come on.
so i removed the screen and took the lvds cable out. there is no burning on the screen end of the cable. i now think the short was possibly on the cable itself not the clip. the wires are shielded so could be shorting internally? but the cable looks ok from the outside. it seems to short the last 2-3 pins on the left side to earth when plugged in but its hard to tell if its due to the burning or the cause of it, these pins are not earthed without the cable, but the cable seems ok on its own as well. i think the connector on the motherboard is a bit damaged inside. it might make the machine un repairable but i plan to buy a new cable and try it. did anyone else find a short on the cable or clip? does anyone have a pinout for the cable?
i have a late 2008 15" unibody with the no backlights. the motherboard has not been liquid damaged. initially on opening the machine i noticed the lvds connector on the motherboard was burnt, it looks like the metal clip that secures the connector had shorted the last few pins on the left side of the connector. i cleaned up the burnt area and insulated the clip, took the motherboard out and found the blown fuse, i decided to bridge the fuse, but the lights still didn't come on.
so i removed the screen and took the lvds cable out. there is no burning on the screen end of the cable. i now think the short was possibly on the cable itself not the clip. the wires are shielded so could be shorting internally? but the cable looks ok from the outside. it seems to short the last 2-3 pins on the left side to earth when plugged in but its hard to tell if its due to the burning or the cause of it, these pins are not earthed without the cable, but the cable seems ok on its own as well. i think the connector on the motherboard is a bit damaged inside. it might make the machine un repairable but i plan to buy a new cable and try it. did anyone else find a short on the cable or clip? does anyone have a pinout for the cable?
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Due the picture under your posting i noticed the place! So i have found it on my logic board, what do i need to do? Just short it or replace? Use my multimeter? (If so please tell me which settings because i don't have an clue how this works...)
Regards, Peter
Do not short it. Replace it. The fuse blew for a reason. Hopefully the reason was temporary due to presence of liquid. But it is possible that a fault remains. Best way to see is to replace it and try. If it works then great. If it blows again then you have a little detective work to do.
First check if the fuse is blown. Put your meter on resistance measurement and check across the fuse. Resistance should be close to zero ohms.
A couple of people in this thread had shorted the fuse and ended up destroying the logic board.
I suspect that the first failure may have been the clip shorting the connector. Later on however, in repeated insertions of the cable it is possible that there is something jammed inside the connector. I have, on 2 occasions suddenly had a short in my connector. When I looked at it under my microscope it appears that what happened was that the connector had peeled up one of the bottom ground contacts and jammed it into the connector pins. I ended up replacing the connector in both cases.
If you are seeing a short it "could" be internally in the cable but from my experience it seems more likely to be the connector. I think I have seen people selling the connector on eBay. It is a 40 pin version. The 13" models use a 30 pin version. Replacing it requires some decent soldering skills and a fine soldering iron. You could see if you can find someone locally who can do it for you.
But you can try the cable first since that is an easier experiment.
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OK i pulled the board out of the macbook, someone ales has already been soldering... damn ebay...
it measures 0.05 on ohm logo 200. am i doing what you meant?
Regards, Peter
Hi Dadioh, thank you very much for the wiring diagram for the cable. I agree with you the short is now inside the connector. I could try to take a wire for PPVOUT LCDBKLT outside of the connector, not ideal but it might work. i may have damaged the motherboard further since bridging the fuse, what would be the next in line to go the 6 pin package to the left of the fuse?
OK i pulled the board out of the macbook, someone ales has already been soldering... damn ebay...
it measures 0.05 on ohm logo 200. am i doing what you meant?
Regards, Peter
Ok. That sounds like the fuse is ok then.
Next step is to measure the resistance between each pin of the WLED chip and ground. You are checking to see if there is a problem with the driver device. Post the measurements here and we will check if something looks amiss. The pins on the driver are very very small. You need fine tip probes to make sure you are measuring just one pin. Where possible it is easier to measure on a component that the track from the driver leads to. Earlier in the thread I posted a link to some fine tip probes that are ideal for these measurements.
The fuse proceeds through a FET to the WLED driver (probably the 6 pin package you mention). The FET can handle a fair bit of current so I would suspect something else further downstream. Most likely the WLED driver. A boundary scan around the WLED driver measuring each pin resistance to ground would be the next step that I would take. Post the readings back here.
However, if the LVDS connector is damaged then you are going to need to replace it. If there is something jammed inside that is shorting pins the best way to handle it is to replace the connector. Not a job I recommend for a novice solderer but if you can find someone who does fine soldering for a living it is a fairly easy job.
ok made a picture:
1=soldered location by old owner is gives 005 @ ohm 200 setting
2=same kinda capacitor gives no reply at all to multi meter! i also noticed this is the capacitor which is shorted on pictures above (few posts back by other person)
going further on wled to ground now
help?
Regards, Peter
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