MacBook Pro Unibody - No Backlight - Logic Board Question

[Dadioh]

hopefully Dadioh can help with my issue. on a mid 09 a1286 2.53ghz, i located the 0402 fuse with the dot. it was properly identified in an earlier post, and its showing on my multimeter that it is not blown. is there any other fuse to check regarding the WLED circuit?

i am having the same issue as others on this thread. computer is fully functional, minus the backlight. thanks for any assistance!

No other fuse so it will likely be an issue with the WLED driver orthe circuitry around it. Or possibly the lvds connector/cable. To troubleshoot that you will need some electronics experience and a schematic. A microscope and fine leads for your multimeter are helpful too.

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I have the A1286 15.4 unibody 2.53ghz. The cable you speak of is it the flat one that sites under the HD? I will look at that.

Sounds like a possibility. I have that same machine but it is my wife's so tearing it apart is an unpopular option

Take a metal object and run around the black border of the glass display. Where it "sticks" is where the sleep magnet is. Then figure out where that lands on the top case and that is where the sensor will be.

 

[neorambo]

Fixed!!!!

No other fuse so it will likely be an issue with the WLED driver orthe circuitry around it. Or possibly the lvds connector/cable. To troubleshoot that you will need some electronics experience and a schematic. A microscope and fine leads for your multimeter are helpful too.

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Sounds like a possibility. I have that same machine but it is my wife's so tearing it apart is an unpopular option

Take a metal object and run around the black border of the glass display. Where it "sticks" is where the sleep magnet is. Then figure out where that lands on the top case and that is where the sensor will be.

I found where the magnet is on the right bottom of the frame of the screen. opened up the case and followed where that connects. I unscrewed where the bottom covers mount to that spine in the case. there is black small piece that connects to the whole next to the drive with two screws there. underneath that there is a orange small cable that leads from the sensor sleep sensor to the motherboard. Here comes the stupid move on my part. The cable was twisted so I was putting the gold leads down. GOLD LEADS TO THAT CABLE MUST BE FACING UP This whole time!!! If I hadn't taken that deal off I would have never found out that it was twisted underneath. Thanks guys and I will continue to surf on this thread to help others with problems

 

[Dadioh]

I found where the magnet is on the right bottom of the frame of the screen. opened up the case and followed where that connects. I unscrewed where the bottom covers mount to that spine in the case. there is black small piece that connects to the whole next to the drive with two screws there. underneath that there is a orange small cable that leads from the sensor sleep sensor to the motherboard. Here comes the stupid move on my part. The cable was twisted so I was putting the gold leads down. GOLD LEADS TO THAT CABLE MUST BE FACING UP This whole time!!! If I hadn't taken that deal off I would have never found out that it was twisted underneath. Thanks guys and I will continue to surf on this thread to help others with problems

Congrats! You get an honorary MacBook detective badge (with gold star

Nothing more satisfying than pulling a nice MacBook back from the brink. Well almost nothing

 

[Alexjones]

I say start over and buy a brand new one from http://store.apple.com/us/browse/home/shop_mac/family/macbook_pro

 

[Dadioh]

I say start over and buy a brand new one from http://store.apple.com/us/browse/home/shop_mac/family/macbook_pro

Wow. Hadn't thought of that. Ok everybody... Just throw your MacBooks in the garbage and buy new ones. In fact, if your house needs new roof shingles just burn it down and build a new one. This is an epiphany!

 

[neorambo]

Wow. Hadn't thought of that. Ok everybody... Just throw your MacBooks in the garbage and buy new ones. In fact, if your house needs new roof shingles just burn it down and build a new one. This is an epiphany!

Your car needs an oil change just leave it on the side of the road and buy a new one. Besides, it's fun to resurrect macbooks from the dead. It gives me a great feeling to be able to fix something, that someone else thought was trash. For those who want to throw away their macbook pros let me know first and I will set a garage can outside your house.

Thanks again Dadioh!

 

[thanhTran]

Thanks

I actually did have one I fixed that had a bad resistor on the enable pin. Going from memory it was something like a 300K 100K voltage divider off the 12V rail giving a 3V signal on the enable pin. It caught me by surprise because resistors rarely fail in my experience. Still not sure what caused that one to blow. But good work diagnosing vyrcoop

Hello Dadioh

Just fixed my cousin's Macbook pro one. Your posts & dedication along with others contributions really help me here.

My board is the same as that of Vyrcoop (https://forums.macrumors.com/posts/13061859/)
And the enable resistor was bad. In my case, the 300K resistor leg was eaten by corrosive liquid (coke from what I was told - it works for several months before dying completely). I don't have any 0402 300K resistor available so I use 3 0603 100K resistors in series, and it fixes the problem.


Thanks very much again for your help Dadioh!

-Thanh

 

[lhkmusic]

Third option. I don't have one in these tiny sizes but I heard there are "easy out" heads that can bite into the screw and back it out. I have larger easy outs for large bolts (like in car repair). They are basically a tapered reverse screw that bite into the crater and screw themselves in. Eventually they bind and will back the screw out.

Dadioh,

this the sort of thing you mean also will this set be small enough ?

http://www.oneclicktools.co.uk/hand...s-&-bolt-grips-micrograbitkit4pc-p-64227.html

 

[Dadioh]

Hello Dadioh

Just fixed my cousin's Macbook pro one. Your posts & dedication along with others contributions really help me here.

My board is the same as that of Vyrcoop (https://forums.macrumors.com/posts/13061859/)
And the enable resistor was bad. In my case, the 300K resistor leg was eaten by corrosive liquid (coke from what I was told - it works for several months before dying completely). I don't have any 0402 300K resistor available so I use 3 0603 100K resistors in series, and it fixes the problem.


Thanks very much again for your help Dadioh!

-Thanh

That is great You may want to put a little kapton tape under the resistors and then maybe some over top to secure it from vibration. But good ingenuity in solving the issue.

 

[Dadioh]

Dadioh,

this the sort of thing you mean also will this set be small enough ?

http://www.oneclicktools.co.uk/hand...s-&-bolt-grips-micrograbitkit4pc-p-64227.html

That looks to be too big. They seem to be made for wood screws.

Your best shot might be the dremel tool slot method.

 

[peislander]

@Dadioh,

Right I managed to get another pic of the front of the motherboard couldn't take one of the back as when I was taking the board out I had a problem with one of the screws, all the others came out except for one which wanted to play silly buggers, so now I have one screw that is threaded, any ideas of the best way of getting this one out ?

Cheers

Liam.

Hey,If your brave enough you can try a drill.Just tape or cover the area around the screw & use a drill bit smaller then the head of the screw.Just go very very slow & keep checking to see if the head will break off.When the head is gone you'll be able to take the motherboard out & get some vise grips on the screw to get it out.I had to do this with a macbook pro battery.Good luck

 

[thanhTran]

That is great You may want to put a little kapton tape under the resistors and then maybe some over top to secure it from vibration. But good ingenuity in solving the issue.

Thanks for the advice Dadioh! Yeah I was afraid of those loosing after a while.
I found 2 0402 620K resistors and put them on top of each other making a 310K resistor and I think I will keep it this way.

On a side note: these MacBook Pros are beautifully made. It surprisingly easier to open than other Dell laptops I've had. On those, there are always several circuit boards stacking on top of each other and beneath the keyboard which you need to remove before you can take them apart.

Thanh

 

[alb404]

Hi,

I'm new to the board and I've been reading this thread from page one to here. I've learned a lot about how LED back light works and I hope I can fix my damaged Macbook Unibody (white, not pro) with your help. Basically, I have the same problem as westbound (see here :here ).

Water damage and no back light. Everything else is OK. I've tested the fuse impedance, and it seems like the fuse is OK (very low impedance). I've read in this thread (see here) that the WLED driver had 6 pins connected to the ground and that a continuity test between ground and on all the pins should give 6x beep. If more, then the WLED driver is dead.

Can someone confirm that? My tests beep on all the pins of the WLED driver.
Are they some more tests i can run to test the driver's integrity ?

Thanks a lot to all the contributors!

Still no one ? I could use some help.

Thanks.

 

[Dadioh]

Still no one ? I could use some help.

Thanks.

Sorry. Must have missed this. There are a lot of posts.

Rather than using the beep mode can you measure the actual resistance from ground to each pin? For example the resistance to ground on the pins should be approximately as shown below. Pin 1 is lower left and counts counter clockwise around the device.

Make sure power is removed from board before testing resistance. Unplug battery or battery connector.

Macbook Pro 13"
Device LP8543 Pin 1 is lower left and counts counter clockwise around the device.
Pin Resistance to ground
1 0
2 1K
3 124K
4 100K
5 0
6 >1M not connected
7 >1M
8 19K
9 0
10 not connected
11 21K
12 >1M
13 >1M
14 >1M
15 0
16 >1M
17 >1M
18 >1M
19 not connected
20 0
21 >1M
22 203K
23 400K
24 290K


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


If your WLED driver is blown you may measure zero or low resistance on some of the pins that are not supposed to be ground.

If anyone has a good board that measures significantly different than these values let me know.

 

[alb404]

Thanks for your answer Dadiho.
Do you have the values for a Unibody not pro (white model) ? That would be great !

Thanks

 

[fishman30]

Hi guys, i'm so glad that i stumbled upon this thread, there's some really great info.

However, my situation is a little different to others. I have the MBP 13 2010, and i replaced one of the hinges because it was very stiff and creaked loudly. I obviously had to remove the screen assembly to do this, and when i put it all back together, the screen was completely blank.
NO backlight and NO faint signal on the display.
I took lots of care with the lvds and connector and do not see any damage. The strange thing is that while the computer is off, i can shine a bright light through the screen and some light travels through to the front. However, when i turn the computer on, the screen goes slightly darker and the torch light does not travel through to the front of the screen. at no point is any data displayed on the screen. The computer does work with an external monitor.

I'm stumped as to what is wrong, and any help or suggestions would be appreciated.

 

[Dadioh]

Thanks for your answer Dadiho.
Do you have the values for a Unibody not pro (white model) ? That would be great !

Thanks

Sorry. Never worked on one of those before. However, find out what the part number on your WLED driver is and if it is the same as either of these then the circuit is likely the same and the values should hold true.

 

[alb404]

Sorry. Never worked on one of those before. However, find out what the part number on your WLED driver is and if it is the same as either of these then the circuit is likely the same and the values should hold true.

I'll have a look tonight, when I get home from work. Thanks !

 

[alb404]

Sorry. Must have missed this. There are a lot of posts.

Rather than using the beep mode can you measure the actual resistance from ground to each pin? For example the resistance to ground on the pins should be approximately as shown below. Pin 1 is lower left and counts counter clockwise around the device.

Make sure power is removed from board before testing resistance. Unplug battery or battery connector.

Macbook Pro 13"
Device LP8543 Pin 1 is lower left and counts counter clockwise around the device.
Pin Resistance to ground
1 0
2 1K
3 124K
4 100K
5 0
6 >1M not connected
7 >1M
8 19K
9 0
10 not connected
11 21K
12 >1M
13 >1M
14 >1M
15 0
16 >1M
17 >1M
18 >1M
19 not connected
20 0
21 >1M
22 203K
23 400K
24 290K


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


If your WLED driver is blown you may measure zero or low resistance on some of the pins that are not supposed to be ground.

If anyone has a good board that measures significantly different than these values let me know.

OK. I got a bit of time to look at the motherboard.

The LED driver used in the white unibody are not the same model as the one you quoted. It's called MC34845.

I've looked the reference up, and found the data sheet from the manufacutere (see here (pdf) and website here). Unfortunately, most of it makes not much sense to me.
One thing caught my attention though. This :

I've tried to locate pin number 14. Here is a picture :

Is this the "FAIL" pin the data sheet mentions? When measuring on this pin, I get 1.16 with my multimeter on 2k ohm. Should I consider that as a 'high impedance" as the data-sheet says?

Here is a picture of what I think is the fuse. I have very low impedance between the two pins, so I guess the fuse is OK.

Anyone ?

Thanks a lot !

 

[Dadioh]

Hi guys, i'm so glad that i stumbled upon this thread, there's some really great info.

However, my situation is a little different to others. I have the MBP 13 2010, and i replaced one of the hinges because it was very stiff and creaked loudly. I obviously had to remove the screen assembly to do this, and when i put it all back together, the screen was completely blank.
NO backlight and NO faint signal on the display.
I took lots of care with the lvds and connector and do not see any damage. The strange thing is that while the computer is off, i can shine a bright light through the screen and some light travels through to the front. However, when i turn the computer on, the screen goes slightly darker and the torch light does not travel through to the front of the screen. at no point is any data displayed on the screen. The computer does work with an external monitor.

I'm stumped as to what is wrong, and any help or suggestions would be appreciated.

Double check that the LVDS connector is fully seated and the locking bale is secured down over the connector. It is possible for the connector to be only inserted part way. Remove battery connection whenever working with the LVDS connector.

----------

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.

 

[fishman30]

Yep, lvds is definitely connected properly. And the battery was disconnected when i worked on it.
I just checked the fuse and its not showing continuity. So the fuse is blown, that would explain the backlight, but not the video, right? So if i replace the fuse, it will be unlikely that it fixes the whole situation? :/

 

[Dadioh]

Yep, lvds is definitely connected properly. And the battery was disconnected when i worked on it.
I just checked the fuse and its not showing continuity. So the fuse is blown, that would explain the backlight, but not the video, right? So if i replace the fuse, it will be unlikely that it fixes the whole situation? :/

The fuse will only affect backlight. Start with that and see where it leads.

 

[therat69]

green led on but no charge

Im new here so sorry if I post this in the wrong thread, I have a 2010MBP that suffered coffee damage, I striped the machine and cleaned it of all signs of stains and let it dry for a few days when I put it together it did not fire up all I get is a bright green led on my magsafe adaptor I have tried a differant adaptor with the same result can come one shed some light on what i need to do to get it working as it should, it will boot up off a charged battery and I can charge the battery on my other MBP but not on this once again sorry if i posted this in the wrong thread

 

[Papabear60]

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?

 

[therat69]

display

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