MacBook Pro Unibody - No Backlight - Logic Board Question

[mayor]

A1278 Early 2011 Backlight Problem

Hello Guys,
I am new at this forum.
I really appreciate all the great advice contained here.
I have a Macbook Pro A1278 early 2011 with no backlight.
Is the Component with the letter "P" a fuse? It is very near the LCD Cable Connector.
I have an open (2MOhms) and I read 12v to gnd. on one leg and 0 on the other.
Any information about a reference number in order to buy it in DigiKey?
Thanks

 

[lhkmusic]

right I still haven't got round to fixing this problem but it now needs doing ASAP, is there anyone in the UK that can help sort this out for me, I have some money to pay and this really needs doing now! So anybody that can help or can point me in the direction of someone that can, please PM me or reply in this thread...

 

[NicoNL]

PM me your email address.

Hm, I just spend some time at the FAQ to find I'm not allowed to send PM's untill I have at least 5 posts...

You can find my email in my contact info (this is at least what I think and hope, but maybe that is also not visible before making 5 posts?).

Anyway, TIA for sending the schematic of the A1278 unibody!
(And I completely agree with your post about being creative...I have made countless "poor man" tools, to solve a problem where the real tool was too expensive or difficult to get)

----------

I had one of these that had an issue with the current sensing resistors being open circuit. The 2008 unibody has a pair of 1ohm resistors in parallel. The 2009 pro WLED driver doesn't use these resistors. You might check those resistors.

Thx. I'll give it a look. Will report later on.

I think I hurried a bit too much in making the conclusion that the APP_1A was faulty. But if the fuse and mosfet are not broken then the control ic is the most logical next one to suspect... And the lack of a datasheet of the APP_1A doesn't help either!

 

[Dadioh]

I need information regarding the backlight problem for Macbook Pro A1278 Early 2011. While trying to replace a broken hinge , I disconnected the LCD cable without noticing that the battery was still connected. After I could not see the backlight but the image is still there if I use a flashlight. Does anyone have component information,schematics, or check points? Thanks

Most likely you have blown the fuse. See the picture in the post by Seahawk up a little further in this thread. If that is the same board you have then the fuse is the component with the "P" on it. Luckily for 2011 owners Apple changed from a tiny 0402 size fuse to a less tiny 0603 fuse which is a little easier to work with.

 

[NicoNL]

I had one of these that had an issue with the current sensing resistors being open circuit. The 2008 unibody has a pair of 1ohm resistors in parallel. The 2009 pro WLED driver doesn't use these resistors. You might check those resistors.

YES!

They were indeed broken down, invisible for the eye but definitely open circuit.
I put one 0603 of 0.5 ohm in place and now have a working backlight!

Don't worry: I'll order a couple of 1 ohm 0603 of 200mW, because it's highly possible that one 0603 of 0.5 can't dissipate enough of the generated heat.

Now I have to repair the charging circuit (this is a really tough one!) and then it's finally working again!

Thanks a lot!!

So, now I have 5 APP_1A's (3 completely unused, one soldered on and off the board and the old one). If there is anyone who needs one of them, just shout...

 

[seahawkgo]

There are some deposits for which isopropyl alcohol is not a good solvent. In those cases water may dissolve them. Dishwasher could work but it depends on the hardness of your water. You don't want minerals left behind on the board when it dries. An alternative would be to get some distilled water and scrub the area in question to see if water is a better solvent for this particular spill residue. Then dry with your heat gun before powering up.

Actually I used WD40 to clean the board, then isopropyl alcohol. I will try to clean it by warm water today.

BTWs, I saved 5 of 2008, 2009 MBP last couple days. But I seem to give up the 2011 i5 A1278 model.

Dadioh, the WLED chip is solderd on the board by balling technology which I bought $7000 station before. Do you know where I can get this WLED IC?

 

[madeagler]

Hello guys!

I'm newbie here and i'm reading this forum and i really wonder of your pro level.

I have got MacBook Pro A1278(Core i5 2.3ghz; MC700D/A), water damaged. I bought it on ebay AS-IS.
It has heavy water damages but it not the worst thing - before someone already tried to repair it, but as i see too unsuccessfully. Broken connectors, bad soldering everywhere.
Notebook does not start at all, even not charging. Thats why i'm looking for board viewer on it in order to recognize the problem(may it's not the only one). I would be very happy if someone will be able to provide this board viewer.

Sorry for my english. I hope you can understand me

MainBoard number: 820-2936-B

Thanks.

 

[naKruul]

Actually I used WD40 to clean the board, then isopropyl alcohol. I will try to clean it by warm water today.

BTWs, I saved 5 of 2008, 2009 MBP last couple days. But I seem to give up the 2011 i5 A1278 model.

Dadioh, the WLED chip is solderd on the board by balling technology which I bought $7000 station before. Do you know where I can get this WLED IC?

I had a hard time finding out which chip apple used but eventually i found out it is a customized National LP8550
You can use this one but you will loose the dithering function (stepless dimming), unless you know how to access the i2c bus in the macbook and reprogramm the WLED driver (i do not)
so just get the LP8550 from national and you are good to go.

 

[lazer155]

How did you find out what part it was?

 

[naKruul]

well first i tried searching for the nummer on the chip, but it is apple proprietary. since national semi is about the only manufacturer who produces 25pin micro BGAs i was able to match a range of chips that would fit. unfortunately that didn't help either. so evetually i got hold of the schematics and luckily apple wrote down the full part number in those...

 

[NicoNL]

PM me your email address.

Yes, but that was not possible till now, because I had no 5 postings. I'll PM you now.

I put another posting about my 13" unibody in the SMC-thread, since that was more appropriate, because the backlight issue is solved, but now my powerbrick/magsave couldn't communicate with the SMC-circuitry.

PS: I still can't PM. Don't know why I'm stiil not allowed...

PS2: I can PM now. You must have a pm from me now.

 

[mullenmouse]

This thread is so useful, hopefully someone can help me...

I bought a Macbook Pro 15" Early 2011 with a black screen. Everything else is working: it boots, charges, shows keyboard backlight, sound etc, but there is no ouput either on the internal or an external screen. Using the info from here and looking at the LVDS connector on the logic board, the first 3 pins are burnout/blackened. I'm assuming this is ONE of the reasons that there is no screen output, but it doesn't explain the issue with external output. Disconnecting the LVDS cable from the board and trying to output straight to the external doesn't work. Could it be that there is something else on the board causing this issue, like a fuse? The board looks perfect apart from the LVDS connector, and I don't know what else to check!

 

[Dadioh]

This thread is so useful, hopefully someone can help me...

I bought a Macbook Pro 15" Early 2011 with a black screen. Everything else is working: it boots, charges, shows keyboard backlight, sound etc, but there is no ouput either on the internal or an external screen. Using the info from here and looking at the LVDS connector on the logic board, the first 3 pins are burnout/blackened. I'm assuming this is ONE of the reasons that there is no screen output, but it doesn't explain the issue with external output. Disconnecting the LVDS cable from the board and trying to output straight to the external doesn't work. Could it be that there is something else on the board causing this issue, like a fuse? The board looks perfect apart from the LVDS connector, and I don't know what else to check!

When you say first 3 pins it is likely those are the pins that carry the backlight voltage. A picture would help us to confirm.

The fuse may be blown for the backlight but that would not explain no output to external display. Start by focussing on the LVDS connector since that is where you notice the burnt/corroded pins.

 

[snowwiz]

L9004 Inductor replacement specifications

I have a bad 30 pin LVDS connector on a 2010 13" MBP. In a futile first attempt at a repair, I think I ended up with too much heat on the top of the board and damaged a component immediately beneath the connector on the bottom side of the board (it glowed a bright orange for about 5 seconds once I reconnected everything and powered back up)

Using a schematic, was able to identify this component as an inductor, Apple part number L9004 (mentioned earlier in this thread at one point). The complete description associate with this component on the schematic is:

"FERR-120-OHM-1.5A 0402-LF"

In trying to spec out a replacement, I have come across several questions:

1. I know "0402" refers to the size of the surface mount component... but does the "LF" that follows have any significance?

2. What does "FERR" refer to... I'm guess iron core, but don't see this as an option when searching on Digikey.

3. "1.5A" I understand to be a current rating, but what does the "120-OHM" refer to? All inductors I see on Digikey are rated in Henries, not ohms...

4. As a general question, I notice on the schematic that some parts are labeled "CRITICAL". Aren't most of the components on the board critical to proper functioning? Can anyone shed some light on what this designation means?

With my limited understanding of the part description, I came up with Digikey part# PCD1891CT-ND, http://www.digikey.com/product-detail/en/ELJ-PF3N3DFB/PCD1891CT-ND/762120

Can anyone confirm if this part will work as a replacement for L9004, and if not, suggest an alternative? Thanks!

 

[mullenmouse]

When you say first 3 pins it is likely those are the pins that carry the backlight voltage. A picture would help us to confirm.

The fuse may be blown for the backlight but that would not explain no output to external display. Start by focussing on the LVDS connector since that is where you notice the burnt/corroded pins.

Best picture I could get.

The rest of the board looks perfect, there doesn't seem to be anything else blown/burnt out.

 

[Dadioh]

Best picture I could get.

The rest of the board looks perfect, there doesn't seem to be anything else blown/burnt out.

Yup. Those would be the backlight pins. Other pins might be a bit dull looking. First step is to replace that LVDS connector and then see.

----------

I have a bad 30 pin LVDS connector on a 2010 13" MBP. In a futile first attempt at a repair, I think I ended up with too much heat on the top of the board and damaged a component immediately beneath the connector on the bottom side of the board (it glowed a bright orange for about 5 seconds once I reconnected everything and powered back up)

Using a schematic, was able to identify this component as an inductor, Apple part number L9004 (mentioned earlier in this thread at one point). The complete description associate with this component on the schematic is:

"FERR-120-OHM-1.5A 0402-LF"

In trying to spec out a replacement, I have come across several questions:

1. I know "0402" refers to the size of the surface mount component... but does the "LF" that follows have any significance?

2. What does "FERR" refer to... I'm guess iron core, but don't see this as an option when searching on Digikey.

3. "1.5A" I understand to be a current rating, but what does the "120-OHM" refer to? All inductors I see on Digikey are rated in Henries, not ohms...

4. As a general question, I notice on the schematic that some parts are labeled "CRITICAL". Aren't most of the components on the board critical to proper functioning? Can anyone shed some light on what this designation means?

With my limited understanding of the part description, I came up with Digikey part# PCD1891CT-ND, http://www.digikey.com/product-detail/en/ELJ-PF3N3DFB/PCD1891CT-ND/762120

Can anyone confirm if this part will work as a replacement for L9004, and if not, suggest an alternative? Thanks!

That is a ferrite bead used for EMI control (reduces radio emissions from the board that would interfere with other electronics). If it smoked then you had significant current passing through it. External heat would not do that. Before you replace the ferrite you should check the resistance to ground to make sure you don't have a short somewhere.

And the 120ohms refers to the impedance of the ferrite at a specific filter frequency. You should measure 0 ohms using a multimeter.

 

[Nslang]

no display, no backlight

Hi,

I have a macbook pro 17 mid 2010 (i5) and I'm having trouble with my screen.
I wanted to fix the airport but now the screen does not switch on, no display, no backlight (and still no airport)
No liquid pill. External monitors are ok.

I've tested the fuse with the beep sound test and it beeps. So what does that means? I noticed that pins 1,2 and 3 of the lvds cable are a bit damaged. I've ordered a new cable but not yet received.
I tested also each pin of the led connector and everything is ok.
Do you know what's the next thing to check ?

Thanks a lot for helping

 

[l.a.rossmann]

If those pins on the LVDS connector are burned you need to replace the LVDS connector. My guess, the fuse did not blow like it is supposed to, so dangerous amounts of voltage ran through the connector frying the pins. This is a tragedy, but can be fixed without much hassle.

 

[Nslang]

If those pins on the LVDS connector are burned you need to replace the LVDS connector. My guess, the fuse did not blow like it is supposed to, so dangerous amounts of voltage ran through the connector frying the pins. This is a tragedy, but can be fixed without much hassle.

Hi, thx for your reply

In fact the LVDS pins on the cable are not burned. I damaged the lvds cable myself by inserting it the wrong way...
The connector is ok, the fuse is ok.
I need to replace the cable as soon as I receive it, it should fix the pb I guess. I'll give a feedback if it solves the pb or not

Cheers

 

[perfumeseksi]

cant find fuse on my macbook air motherboard

Hi guys, could somebody help me to find fuse on my macbook air? Would be very grateful guys.

 

[matt.irepair]

First of all I'd like to just say major props and thanks to everyone that's helping us figure these boards out!Without your guys help this wouldn't be possible and it's so awesome for me to being to understand what really makes these things "tick".

I've got a 2011 MBP 13" w/no backlight that I got from a college kid on a rainy night for a little over $200,it had wine spilled on it.I ran the serial # and it still has AppleCare!I was elated when I figured that out but it seems I pushed my luck a little at our only AppleCare Repair center.They fixed the last MBP I brought them that was water damaged no questions asked (under AppleCare too) but no luck this time.Oh well I am still very grateful for that first one but now I'm wondering what I should do with this one.I finally found the Backlight fuse last night and it looks like one of the posts is broken off!There is also a little corrosion around it,but it looks to me like the fuse was blown off but I am wondering is this normal?Does it ground straight to the board and only require the one post?Or is it blown just like I suspect?What is odd is that the one end that's corroded doesn't even have the place for it to be soldered onto it just looks like straight board no metal or anything.I've cleaned the board with just basic 75% iso alc and air blasted it but have not tried a ultrasonic cleaner.Any advice from any gurus?It would be greatly appreciated!!!

BTW Thanks Rossman for the 15" MBP LCD coming in the mail(eBay),you're saving my you know what.$65 shipped seems so low!How do you even make money at that price???You're awesome man

 

[seahawkgo]

I had a hard time finding out which chip apple used but eventually i found out it is a customized National LP8550
You can use this one but you will loose the dithering function (stepless dimming), unless you know how to access the i2c bus in the macbook and reprogramm the WLED driver (i do not)
so just get the LP8550 from national and you are good to go.

Can you give me the part link from national for the LP8550?

 

[arthurwayne]

Hello everyone. I have a problem with audio on my A1297 (820-2849-A)
The built-in speakers on a laptop stopped working. When I move the audio jack (port) the sound comes and goes. According to the most popular solution I have tried to short the contact with the help of toothpick. After that the sound has gone completely though In the OS the sound card is enabled and active. Unfortunately I’m unable to take my laptop to Apple Service Center since I bought it in the US but I’m a resident of Russia. Repair in Russia is possible but it’s very expensive and time consuming. So I disassembled the laptop myself and realized that the audio port is to be replaced. I failed to disassemble the entire logic board therefore I can’t understand which spare part I need to buy to fix it. If you could offer me your right solution or give me the part number the of audio input from the logic board #820-2849-A or schematic I would highly appreciate that.

 

[l.a.rossmann]

Hi guys, could somebody help me to find fuse on my macbook air? Would be very grateful guys.

What is the 820- part number of your board?

820-2101-A?

820-2249-A?

820-2530-A?

It will look like the above.

Tell me your number and I will find you your fuse.I have one of every board from 2006-present sitting here, sans 1 or 2 unpopular/obsolete models. I'd be happy to post a picture with an arrow to the components in question.

 

[kilgrinus]

Help

Lots of great info on this thread and now I'm hoping you guys can help me out. I have a 2009 MBP 13 with no backlight. I have replaced the fuse, WLED driver,LCD, and LVDS cable but still no backlight. I have 3 volts on enable pin (4 of WLED) and 12 volts on both sides of the boost diode.