MacBook Pro Unibody - No Backlight - Logic Board Question

[atomton]

Hey guys,

I've been reading this topic for a while, but now I need some advice. I've got a Mid 2012 MacBook Pro 15" (A1286) here, logic board is 820-3330-B. It had a bad coffee spill, but after cleaning it, everything except the keyboard worked again. After changing that, the display backlight stopped working.

The fuse appears to be fine, but I'm only measuring 12V at what I think is the boost diode and on the LVDS connector pins. Unfortunately I didn't find the schematics yet, so I wasn't really able to test the LED driver (I think it's a LP8550). Attached is an image of the section where the parts are located. Does anyone have an idea how to proceed now?

Link to the Image

Thanks!

 

[GoTimothy]

Hi Guys ,
Any chance you guys can let me know where i can get hold of the this fuse?
Image

thanks[/QUOTE]

I’m not sure but, I don’t think that is a fuse. The dot is usually a P For power. The green thing in that picture Marked F150 with 24 BELOW IT MIGHT BE A 24 V FUSE. It has those two little indents on it for checking with a multimeter. Check it for continuity, if there’s no connection, it might be a blown fuse. If there’s continuity than either it works or it’s a resistor.

But don't take my Advice I'm new here, ask someone else To confirm.

 

[GoTimothy]

Hey guys,

I've been reading this topic for a while, but now I need some advice. I've got a Mid 2012 MacBook Pro 15" (A1286) here, logic board is 820-3330-B. It had a bad coffee spill, but after cleaning it, everything except the keyboard worked again. After changing that, the display backlight stopped working.

The fuse appears to be fine, but I'm only measuring 12V at what I think is the boost diode and on the LVDS connector pins. Unfortunately I didn't find the schematics yet, so I wasn't really able to test the LED driver (I think it's a LP8550). Attached is an image of the section where the parts are located. Does anyone have an idea how to proceed now?

Link to the Image

Thanks!

Same thing to you. I believe the green thing with the 24 written on it is a Poly fuse at the top of your picture. I’m not certain because I’m not into electronics but Check out this fuse on eBay

http://www.ebay.com/itm/FUSE-PTC-RESETTABLE-24V-2A-2920-2920L200-24DR-2309127-/271286587867?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item3f29f0d1db

You can check the continuity to see if it’s a resistor or fuse. No continuity would be a blown fuse if there’s continuity then it’s good whether it’s a fuse or a resistor.

Then if you’re careful and you can work with the power on the laptop, you can check one side of it to see if it reads 24 V. If the other side is dead it’s probably a blown fuse.

Or just Wait for somebody with experience to give you advice.

 

[atomton]

Same thing to you. I believe the green thing with the 24 written on it is a Poly fuse at the top of your picture. […] You can check the continuity to see if it’s a resistor or fuse. No continuity would be a blown fuse if there’s continuity then it’s good whether it’s a fuse or a resistor.

Then if you’re careful and you can work with the power on the laptop, you can check one side of it to see if it reads 24 V. If the other side is dead it’s probably a blown fuse.

I just measured it, there is continuity, and I get around 12.5V on that green thing, which is basically the same voltage I get on the components mentioned in my post before.

 

[GoTimothy]

I just measured it, there is continuity, and I get around 12.5V on that green thing, which is basically the same voltage I get on the components mentioned in my post before.

Well I found one of those little things with a dot on it on my dead MacBook and it seems to be closed, so I guess they’re right it is a fuse. That Macbook won’t boot.

The one am trying to get working, is the one that boots with the back light that don’t work. I will settle if I can get this one to boot.

Is the thing with a white dot on it, an open circuit on yours?

 

[atomton]

Well I found one of those little things with a dot on it on my dead MacBook and it seems to be closed, so I guess they’re right it is a fuse. That Macbook won’t boot.

The one am trying to get working, is the one that boots with the back light that don’t work. I will settle if I can get this one to boot.

Is the thing with a white dot on it, an open circuit on yours?

Well my MBP doesn't have a white dot fuse, but rather that P fuse. I have 12.44V on it (according to the schematic, the fuse has something to do with PPBUS_S0_LCDBKLT, and that should be around 12.6V). Basically the MBP is working properly, except for the backlight. External displays work.

 

[GoTimothy]

Well my MBP doesn't have a white dot fuse, but rather that P fuse. I have 12.44V on it (according to the schematic, the fuse has something to do with PPBUS_S0_LCDBKLT, and that should be around 12.6V). Basically the MBP is working properly, except for the backlight. External displays work.

You said you tested your fuse continuity and it worked, but then you said you were looking to buy one. My P Fuse has no continuity and I have no black light so I ordered 50 of them from eBay. They will sell you one but it will cost about the same price. I figured I might lose a few or burn a few up before you get it to work.

This is not an advertisement I am just showing you what I bought. If someone needs one I can send them one for free when I get them.
FUSE 3A 32V FAST ACTING SMD 0603 Littelfuse CHIP FUSE NEW LOT QTY: 50 FUSES

http://www.ebay.com/itm/141079832861?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

I ordered a fuse from another guy on eBay who said it was for Mac book Pro but that was one of those tiny fuses and it didn’t even have a small dot on it. It was so small I had to put it under a microscope to see it. The P. Fuses are little bigger. lol

 

[bosna1973]

2008 macbook pro 15 with battery works perfect but do not charge if anybody can help me identify this chip in red on pic(K84V9)

 

[mattiahalter]

external backlight source

I was wondering if it is a bad idea to power the backlight with an external power source?
In the schematics for the LVDS connector (early 2011 13") I found that pin 21 and 22 are connected to PPVOUT_S0_LCDBKLT.

Is this a very bad idea?


This thread already helped me a lot. Since a lot of people had exactly the same problem (video but no backlight because of water spill) I know what parts to check.

I will check as soon as possible if the fuse is burned and so on.... But if I cant find the damaged part, I thought I could try to externally power the backlight.

Regards

 

[macrepair]

MacBook Air 2013 WLED BGA driver

Does anyone know what this part number is please for 2013 MacBook Air which I think is the BGA WLED driver? Tiny 2.5mm x 2.5mm package.

Part shows number on top shows 2CXH D688

 

[atomton]

So, with some help I was able to find the backlight circuitry and meter some stuff. Maybe someone has an idea what could be wrong.

Just for the records, it's an A1286, Mid-2012 15" MacBook Pro, logic board 820-3330-B, WLED driver LP8550.

FDC638APZ
LCDBKLT_EN_DIV: 4.18V
PPBUS_SW_LCDBKLT_PWR: 12.58V
The 12.58V actually continue throughout the boost circuit, eventually arriving at the LVDS connector pins (PPVOUT_S0_LCDBKLT).

Q9707 (n-ch mos x2)
LCDBKLT_EN_L: 0V
LCD_BKLT_EN: 3.3V
LCDBKLT_DISABLE: 0V
BKLT_PLT_RST_L: 3.3V

LP8550
BKL_EN: 3.1V
BKL_PWM: 0-2.9V (min-max brightness setting)
BKL_ISEN1-6: 0V (LED_RETURN)
PP3V3_S0_BKL_VDDIO: 3.3V
SWx: 12.58V
FS: 12.58V
PP5V_S0: 5V

One thing appears strange though, I was able to meter all the resistors within a second each, but at the 301K+100K in the BKL_EN area, the DMM is not able to show the value, but it's starting at 150K+70K and slowly increasing the value (as a reference, the other 301K in proximity to the fuse is showing 301K within a second).

UPDATE: A different multimeter shows 2.9V at the BKL_EN pin of LP8550.

 

[GoTimothy]

I bought a MPB on eBay that had a busted screen that was torn off the laptop and did not light up. I bought another laptop on eBay that the motherboard was missing, to try to make one good laptop. When I hook them up, the motherboard started smoking and the LCD did not light up. Laptop still worked on an external monitor.

The laptop with the motherboard missing, had the LCVD cable, that looked like it was pulled off, as the clip was missing. A real hack ripped this laptop apart. He might have pulled the cable off the LCD screen, under the glass, which I don’t want to remove. This screen may have fried my main board or it could because the cable did not connect well.

The screen that the glass was broken, might have a good LCD. I took OHM readings on the 30 pins on both LCD’s.

I am wondering if one is good and the other is bad, if they’re both bad, good or what. Here’s my readings on the 2011 13" 30 pin display cable. They are both pretty much the same except for pin number five.

Can anyone give me a OHM reading on pin number five, from a disconnected from the motherboard cable, of a 2011 MBP 13" or if these reading are ok? Schematic says it’s a TP_BKL_SYNC line

I don’t want to replace the fuse and resistors just to have them fry again, if the LCD is bad. I think I might have got both of these laptops from someone who tried to fix them on this website. It’s frustrating if you don’t know what is bad or what is good.

LCD 1

pins
1. .5 Ground cable
2. 2.385
3. 2.385
4. 0.f
5. 11.72 to 11.85 varies
6 Threw 18 Pins the same 0.f
19. .4
20 Threw 30 Pins the same 0.f


LCD 2
pins
1. .5
2. 2.338
3. 2.338
4. 0.f
5. 2.582 to 2.604 varies but far from LCD 1
6 Threw 18 Pins the same 0.f
19. .4
20 Threw 30 Pins the same 0.f

LCD 3 from a 2009 13" 30 pin that laptop won’t boot
pins
2. 5.000
3. 5.000
5. 1.915

 

[triplelucky]

Does anyone know what this part number is please for 2013 MacBook Air which I think is the BGA WLED driver? Tiny 2.5mm x 2.5mm package.

Part shows number on top shows 2CXH D688

Looks like it could be an LP8550.

 

[GoTimothy]

LCVD Cable Clip Repair

Got the 13 inch MBP back light working. Replaced the fuse, don’t look too bad for soldering with a 25-year-old RadioShack iron. http://www.Timothean.com/FixFu.jpg

I fixed the clip with a .003 x .050 shim that I rolled around the clip. http://www.Timothean.com/FixLcd.jpg

If it doesn’t seem to hold I will put a little solder here. http://www.Timothean.com/FixLcdS.jpg

Least I did not have to remove the glass.

The LCD was good at the readings I posted and the fried resisters seem to still work.

 

[t0p0ne]

Well my MBP doesn't have a white dot fuse, but rather that P fuse. I have 12.44V on it (according to the schematic, the fuse has something to do with PPBUS_S0_LCDBKLT, and that should be around 12.6V). Basically the MBP is working properly, except for the backlight. External displays work.

My MBP 13" A1278 2011 i5 logic board 820-2936-A is doing the same thing, got water damaged, cleaned the board and it has worked for a good 2 weeks and now backlight went out all the sudden, everything's still working fine but dim screen. I've checked the fuse is good but haven't done much testing because i don't have a solid lead as where to start looking, will check the WED driver and small components surround it and will report back
In the meantime if anyone has a better idea please kindly reply here
Thanks

----------

Got the 13 inch MBP back light working. Replaced the fuse, don’t look too bad for soldering with a 25-year-old RadioShack iron. http://www.Timothean.com/FixFu.jpg

I fixed the clip with a .003 x .050 shim that I rolled around the clip. http://www.Timothean.com/FixLcd.jpg

If it doesn’t seem to hold I will put a little solder here. http://www.Timothean.com/FixLcdS.jpg

Least I did not have to remove the glass.

The LCD was good at the readings I posted and the fried resisters seem to still work.

Which one did you fix? a 2011 13" MBP? I have backlight issue too might check against your lvds connector readings, the fuse on mine is fine though, it shows 12.3V and measured 0.2 Ohm

 

[atomton]

My MBP 13" A1278 2011 i5 logic board 820-2936-A is doing the same thing, got water damaged, cleaned the board and it has worked for a good 2 weeks and now backlight went out all the sudden, everything's still working fine but dim screen. I've checked the fuse is good but haven't done much testing because i don't have a solid lead as where to start looking, will check the WED driver and small components surround it and will report back
In the meantime if anyone has a better idea please kindly reply here
Thanks

You could also check the rest of the backlight circuit.

In my case, everything appears to be working except for the 301K/100K voltage divider in the enable circuit, and there might be an issue with the display tool since it doesn't have backlight when connecting it to a working logic board. Yet a different (working) display has no backlight when connecting it to the bad logic board. I just wonder if the LED return lines should carry a specific voltage or something, because they're all 0V.

 

[t0p0ne]

You could also check the rest of the backlight circuit.

In my case, everything appears to be working except for the 301K/100K voltage divider in the enable circuit, and there might be an issue with the display tool since it doesn't have backlight when connecting it to a working logic board. Yet a different (working) display has no backlight when connecting it to the bad logic board. I just wonder if the LED return lines should carry a specific voltage or something, because they're all 0V.

I've checked with a working LCD unit but it's not it, do you have the correct voltage output around LP8550? I can find 2 resistors carry 3V and 2 caps carry 5V surrounding LP8550, i'm wondering what's the correct voltages are and not sure whether or not it's LP8550 issue

 

[cactus.jack]

circuit diagrams for the motherboard of the MBP A1286 B- 820-2523 B

Thanks Mori, on this pic it is a brown one, but if i remember it right, mine was white. Would this be a capacitor too?

EDIT: I managed to find a diagram of my motherboard. I'm not a good diagram reader, can someone read the diagram and tell me if they see the component by chance?

Cheerz

ps. i got the all the circuit diagrams for the motherboard of the MBP A1286 B- 820-2523 model(the mid 2009 2,8GHZ) if somebody needs it, pm me

First off Hello to everyone here in this forum !
I´ve read the whole thread thru. Took half the day. Very informative and I learned a lot about the mac book circuitry.

I have a question for Felixius. You stated in the quoted thread, that you have the schematics for the A1286 Board (820-2523 B). I have that mac book Pro 15" with exact this problem discussed in this thread. could it be possible that you or one of the other members here have those schematics yet and maybe also the Boardview file for this main-board?

You would make my day if I could get hold of these files. Since I just signed up . I dont know if personal messages are allowed. I did turn on the email function though.

It´s a great forum and the guys here in this thread receive my thanks for sharing their knowledge and findings with the rest of the community.

 

[cactus.jack]

First off Hello to everyone here in this forum !
I´ve read the whole thread thru. Took half the day. Very informative and I learned a lot about the mac book circuitry.

I have a question for Felixius. You stated in the quoted thread, that you have the schematics for the A1286 Board (820-2523 B). I have that mac book Pro 15" with exact this problem discussed in this thread. could it be possible that you or one of the other members here have those schematics yet and maybe also the Boardview file for this main-board?

You would make my day if I could get hold of these files. Since I just signed up . I dont know if personal messages are allowed. I did turn on the email function though.

It´s a great forum and the guys here in this thread receive my thanks for sharing their knowledge and findings with the rest of the community.

No one here, who could help... any chance that someone knows a good place to get the boardview files, schematics for macbooks and other notebook mainboards

would make me quite happy, if someone could help

 

[dieett]

mbp K19 Schematic

No one here, who could help... any chance that someone knows a good place to get the boardview files, schematics for macbooks and other notebook mainboards

would make me quite happy, if someone could help

Here:
http://pingguoweixiu.com/usr/uploads/2012/01/2107445118.pdf

greetings from germany

 

[vondr]

No screen backlight A1278

Hey, I have tried to get my backlight working but no success. I have measure all the pins on the WLED driver and everything seems to be ok. The 2A fuse i working. When I measure the voltage on the 4 pin on the WLED driver the voltage is 0V. There is no backlight voltage. I have tried to put 3V directly to pin 4 on the WLED driver, but nothing happens. Is there more fuses on the other side of the logic board because I have measure all the component on this side (se picture) and everything seems to be ok.

Edit: Welded a cable from the fuse to the resistor before the WLED driver, this gave me 2.6V to the 4 Pin. Now the backlight voltage is ok, but the backlight just flickering and you can't really se whats on the screen because its still quite black. Even when I turn the computer off the backlight is still flickering. What can I do?

 

[h4lp m3]

Hey, I have tried to get my backlight working but no success. I have measure all the pins on the WLED driver and everything seems to be ok. The 2A fuse i working. When I measure the voltage on the 4 pin on the WLED driver the voltage is 0V. There is no backlight voltage. I have tried to put 3V directly to pin 4 on the WLED driver, but nothing happens. Is there more fuses on the other side of the logic board because I have measure all the component on this side (se picture) and everything seems to be ok.

Edit: Welded a cable from the fuse to the resistor before the WLED driver, this gave me 2.6V to the 4 Pin. Now the backlight voltage is ok, but the backlight just flickering and you can't really se whats on the screen because its still quite black. Even when I turn the computer off the backlight is still flickering. What can I do?

Did you ever figure this out? Can you tell me which one is the fuse? Is it the one labeled 74 or the white one above it?

 

[vondr]

Did you ever figure this out? Can you tell me which one is the fuse? Is it the one labeled 74 or the white one above it?

No, I have order the WLED driver, I will try to replace this and test (2 weeks delivery time). 74 is not a fuse its a kind of resistor making 27V to the LED display. The little thing with a dot is the fuse.

 

[joenot443]

A1286 backlight liquid damage

Hi all,

Like many in this thread, after an unfortunate liquid spill on my MacBook, I've lost all capabilities of the machine's backlight. The rest of the computer works fine - the image can be displayed on an external monitor and if a light is shone through, the image can be seen on the laptop's screen as well. The only issue lies in the backlight.

It is an early 2011 15' MacBook Pro. I have attached some photos of the affected logic board areas, I have already cleaned them as best I can with rubbing alcohol, unfortunately to no avail.

It appears as if the two leftmost pins on the LVDS connector cable have either been corroded or broken off. Could it be possible this is the issue?

If not, could someone point out the areas on the board I should be testing with a multimeter in order to find the faulty fuse?

Mostly I'm just looking for someone to point me in the right direction.

Thank you very much for your help!

 

[Dadioh]

Hi all,

Like many in this thread, after an unfortunate liquid spill on my MacBook, I've lost all capabilities of the machine's backlight. The rest of the computer works fine - the image can be displayed on an external monitor and if a light is shone through, the image can be seen on the laptop's screen as well. The only issue lies in the backlight.

It is an early 2011 15' MacBook Pro. I have attached some photos of the affected logic board areas, I have already cleaned them as best I can with rubbing alcohol, unfortunately to no avail.

It appears as if the two leftmost pins on the LVDS connector cable have either been corroded or broken off. Could it be possible this is the issue?

If not, could someone point out the areas on the board I should be testing with a multimeter in order to find the faulty fuse?

Mostly I'm just looking for someone to point me in the right direction.

Thank you very much for your help!
Image

Image

Image

Those last three pins are the backlight pins so at a minimum you need to replace the LVDS cable. You also need to look inside the LVDS connector because it is possible that the interior pins are also corroded or plastic melted in that corresponding connection.

The fuse is identified in my attachment. That is likely blown.