MacBook Pro Unibody - No Backlight - Logic Board Question

[fanis.gourlemak]

Hello to everyone.I m from Greece and new to the forum and kind of young but i like these kind of things and want to find a solution on my own.I have read many pages from the beginning of this famous topic and some before the last one,so i got the general idea.Probably, i could answer my own questions by reading again and again but i think its more reassuring to have your approval to my thoughts.So to the topic...

I have a mid 2010 13" macbook pro A1278.My backlight stopped working 2 days ago when i disassembled it for the first time ,following an ifixit guide,to change my thermal paste.I changed it,put all the stuff together and turned it on.It was when i saw the backlight was't working.My screen has signal as i can see the login screen with the flash of my mobile and when i connect it to a monitor ,everything is fine except the backlight.

So,i suppose from the things being said here:

1st. I have to measure the resistance on my fuse.If i see 1-10 ohms its fine.Bigger numbers like megaohms means its blown so i change it.

2nd. If the fuse is ok i test the diode above her. If the cathode of that diode is approximately 27V there then the issue is either the LVDS cable or the display so i change the cable first most likely.If i see no voltage at all, then the problem is the WLED circuit(L8545) which i have to measure each one of the tiny legs to be sure.

I have located the above stuff on my board so if you reassure my thoughts im moving to measurements.And coming back with updates.Do you know any stores in Europe to order these things?Except the LVDS cable or the screen in case i need these,which i can find them on ebay.

And one last question.In the pages i've read,most of the people have the problem on their fuse marked with a "dot" or a "P" depending on the model.So why the IMPORTANT NOTE in the first post by Dadioh says that the problem isn't a fuse but a high frequency capacitor ?

Thanks in advance and despite the fact that i don't have all the tools needed i hope i can fix my laptop as many have done here.

 

[Rickkap]

Hello to everyone.I m from Greece and new to the forum and kind of young but i like these kind of things and want to find a solution on my own.I have read many pages from the beginning of this famous topic and some before the last one,so i got the general idea.Probably, i could answer my own questions by reading again and again but i think its more reassuring to have your approval to my thoughts.So to the topic...

I have a mid 2010 13" macbook pro A1278.My backlight stopped working 2 days ago when i disassembled it for the first time ,following an ifixit guide,to change my thermal paste.I changed it,put all the stuff together and turned it on.It was when i saw the backlight was't working.My screen has signal as i can see the login screen with the flash of my mobile and when i connect it to a monitor ,everything is fine except the backlight.

So,i suppose from the things being said here:

1st. I have to measure the resistance on my fuse.If i see 1-10 ohms its fine.Bigger numbers like megaohms means its blown so i change it.

2nd. If the fuse is ok i test the diode above her. If the cathode of that diode is approximately 27V there then the issue is either the LVDS cable or the display so i change the cable first most likely.If i see no voltage at all, then the problem is the WLED circuit(L8545) which i have to measure each one of the tiny legs to be sure.

I have located the above stuff on my board so if you reassure my thoughts im moving to measurements.And coming back with updates.Do you know any stores in Europe to order these things?Except the LVDS cable or the screen in case i need these,which i can find them on ebay.

And one last question.In the pages i've read,most of the people have the problem on their fuse marked with a "dot" or a "P" depending on the model.So why the IMPORTANT NOTE in the first post by Dadioh says that the problem isn't a fuse but a high frequency capacitor ?

Thanks in advance and despite the fact that i don't have all the tools needed i hope i can fix my laptop as many have done here.

Hi and welcome to the Forum

Check the fuse, which from your description is the most likely problem. Put your multi-meter in continuity mode and check that the fuse bleeps. Or you can put the meter in resistance mode and any resistance display and the fuse is fine.

This is the fist check you must do before looking at anything else.

Report back when you have done this and we will take the next step.

 

[Dadioh]

I have a mid 2010 13" macbook pro A1278.My backlight stopped working 2 days ago when i disassembled it for the first time ,following an ifixit guide,to change my thermal paste.I changed it,put all the stuff together and turned it on.It was when i saw the backlight was't working.My screen has signal as i can see the login screen with the flash of my mobile and when i connect it to a monitor ,everything is fine except the backlight.



And one last question.In the pages i've read,most of the people have the problem on their fuse marked with a "dot" or a "P" depending on the model.So why the IMPORTANT NOTE in the first post by Dadioh says that the problem isn't a fuse but a high frequency capacitor ?

Thanks in advance and despite the fact that i don't have all the tools needed i hope i can fix my laptop as many have done here.

Since this is not a liquid damage failure but rather it occurred after disassembly and reassembly then the problem is likely damage to the LVDS connector. They are quite delicate and if the cable is not carefully inserted into the logic board connector it is possible to bend pins inside the connector or damage the cable itself.

I would remove the cable from the connector and examine the pins inside the connector for damage. You will need to tilt the MacBook on edge to see into the connector. Or best if you can remove the logic board to get a better view. best to use some sort of magnification since the pins inside are quite small. Also examine the cable end carefully for signs of damage.

The comment on the first page concerning the capacitor was that I did not initially know that the white component was a capacitor. I thought it might be a fuse. I wanted to make sure that people do not replace it with a fuse. The smaller fuse is actually labeled with a dot or a P. The dot means 2A fuse and the P means a 3A fuse.

 

[fanis.gourlemak]

Thank you for your answers .Really appreciate it.

I thought also of the LVDS connector because when I tried to disconnect it for the first time I kind of broke the little thin gold piece of metal on top ,from the one side.Here is a photo showing it a bit of dislocated.

Also when I was trying yesterday to connect my monitor there was a problem.the image appeared for half a second only on the monitor and then went black without showing the "no signal" message.
But today I disconnected and connected again the LVDS cable and the monitor worked.but I was in a hurry and forgot to disconnect the battery while disconnecting the cable.so maybe by that way I damaged sth else. Here are photos of the cable and the inside of the connector.best I could
take..

 

[fanis.gourlemak]

The cable and connector seems fine to my inexperienced eye.Should I move forward and find access to a multimeter so that I can start measurements??

 

[fanis.gourlemak]

UPDATE.
just now I checked the fuse and put the multimeter I got access in continuity mode and the fuse doesn't "beep".also when I tried to measure the ohms I got no reading in neither of the options on the ohms.

So the final result is to change the fuse right??Something else I m missing??

 

[Rickkap]

UPDATE.
just now I checked the fuse and put the multimeter I got access in continuity mode and the fuse doesn't "beep".also when I tried to measure the ohms I got no reading in neither of the options on the ohms.

So the final result is to change the fuse right??Something else I m missing??

No, the fuse is blown... your need to change that. Just before you do change it just check that you haven't got a short otherwise when you put a new one in it will also blow!!!

To check for a short put your multi-meter in Diode mode and put the red probe on ground and the black probe on either side of the fuse, you should get 0.54 as a reading on both sides...

Regards

Rick

 

[fanis.gourlemak]

I think in the multimeter I have in front of me the Diode mode is the same as 2K Ω.If we suppose I am right i grounded the red probe in one of the metal holes of the board and I get 0.53 on one side of the fuse but on the other side i get nearly 1.36 ...

 

[Rickkap]

I think in the multimeter I have in front of me the Diode mode is the same as 2K Ω.If we suppose I am right i grounded the red probe in one of the metal holes of the board and I get 0.53 on one side of the fuse but on the other side i get nearly 1.36 ...

That's ok... change the fuse and try and fix the top of the Lvds connector.

 

[fanis.gourlemak]

By "the top of the lvds connector" you mean that little thin piece of metal that I have posted in the previous post ??

How you suggest to fix it? The cable connects just fine in the socket and the little piece of metal goes in its place when the cable is there...

Also, do you know any possible reasons this thing happened ??

 

[Rickkap]

By "the top of the lvds connector" you mean that little thin piece of metal that I have posted in the previous post ??

How you suggest to fix it? The cable connects just fine in the socket and the little piece of metal goes in its place when the cable is there...

Ok that's fine, I wasn't sure it the connector would fit back in ok. Change the fuse and see how you get on...

 

[fanis.gourlemak]

Thank you for your answers..I will try my best and post again here the results.

 

[fanis.gourlemak]

Hey guys. Hello again.I have a question about the fuses.

do these fuses shown here are suitable for our job or do I have to find others??: http://www.tme.eu/gr/katalog/asfaleie_-smd-0402-upertacheia_-tixi__113150/
They have the same characteristics though.

I think they are in Europe cuz I'm form Greece but the others shown in previous posts ,from america, seem to be closer to that of the board...

 

[Rickkap]

Hey guys. Hello again.I have a question about the fuses.

do these fuses shown here are suitable for our job or do I have to find others??: http://www.tme.eu/gr/katalog/asfaleie_-smd-0402-upertacheia_-tixi__113150/
They have the same characteristics though.

I think they are in Europe cuz I'm form Greece but the others shown in previous posts ,from america, seem to be closer to that of the board...

Not sure as it's in Greek, have you looked on eBay? what's the model number of the logic board?

I think you have a 820-2327 board, it's a 2A - 32v 0402-hf fuse.

http://www.tme.eu/en/katalog/#id_ca...18,38&used_params=18:38847;35:19043;77:24741;

 

[fanis.gourlemak]

UPDATE.
Hello again. I did my try and tried to change the fuse.it's so small.so small.
And it doesn't look like very good.here is a photo.

The problem that i have now is that the laptop doesn't start up at all.not even the fan.any suggestions?

 

[Rickkap]

UPDATE.
Hello again. I did my try and tried to change the fuse.it's so small.so small.
And it doesn't look like very good.here is a photo.


The problem that i have now is that the laptop doesn't start up at all.not even the fan.any suggestions?

Re-check your work as the backlight fuse has nothing to do with turning the laptop on.

Can you upload a better/clearing pics for us to have a look at

 

[davg]

Hi guys I am wrestling with a MacBook Air med 2011 that has no backlight nor any sign of video at all other than that the computer works just fine plugged into an external monitor? Could this be a bad fuse and can someone help with some test points to try I can't seem to find a fuse and I don't have a schematic, I do have a multimeter and can manage. Attached is a photo of the board both sides. Hope someone can help

 

[Rickkap]

Hi guys I am wrestling with a MacBook Air med 2011 that has no backlight nor any sign of video at all other than that the computer works just fine plugged into an external monitor? Could this be a bad fuse and can someone help with some test points to try I can't seem to find a fuse and I don't have a schematic, I do have a multimeter and can manage. Attached is a photo of the board both sides. Hope someone can help

Hi, it's located on the second picture. Where the battery connector is to the left of that is a Grey box. It's above that with the letter P on it

 

[davg]

Hi, it's located on the second picture. Where the battery connector is to the left of that is a Grey box. It's above that with the letter P on it

Thanks for the prompt reply Rickkap!! found it, rather small but it is good, got continuity across it. Was hoping it was a simple fuse?? Any idea what would cause these symptoms?? "Totally black screen" no video no backlight?? The MacBook Air work fine with an external monitor attached.

 

[Rickkap]

Thanks for the prompt reply Rickkap!! found it, rather small but it is good, got continuity across it. Was hoping it was a simple fuse?? Any idea what would cause these symptoms?? "Totally black screen" no video no backlight?? The MacBook Air work fine with an external monitor attached.

Have you tried another LCD? check the LVDS Connector, I think Pins 3,4 should be around 20-30v. What's the history behind this MBA?

If you don't have the high voltage on pins 3,4 you need to start looking at the LP8550. I've circled it but your really need the schematics/boardview to make sure that's the correct chip.

What's the 820- number of the board?

 

[davg]

Have you tried another LCD? check the LVDS Connector, I think Pins 3,4 should be around 20-30v. What's the history behind this MBA?

If you don't have the high voltage on pins 3,4 you need to start looking at the LP8550. I've circled it but your really need the schematics/boardview to make sure that's the correct chip.

What's the 820- number of the board?

Thanks again and yes I did try another lcd and maybe I shouldn't have?? a one from a MacBook Pro but it didn't work it was the same connection but not sure the same pin out? If you look close at the picture just in front of the lvds connector something has burned? I think this happened when I plugged in the MBP Lcd? The connector looks ok I have not checked the voltage on the pins I have the board out?? I don't know the history on the unit I picked it up in a package deal The board # 820 3023-A

 

[Rickkap]

Thanks again and yes I did try another lcd and maybe I shouldn't have?? a one from a MacBook Pro but it didn't work it was the same connection but not sure the same pin out? If you look close at the picture just in front of the lvds connector something has burned? I think this happened when I plugged in the MBP Lcd? The connector looks ok I have not checked the voltage on the pins I have the board out?? I don't know the history on the unit I picked it up in a package deal The board # 820 3023-A

Dude... MBP & MBA are not compatible!!!!! I can't see the burnt item, but I would be thinking of a) finding out what that is and b) replacing that first. Google for your schematics and board view files. If you want to take a closer pic of the burnt bit I will try and identify the item for you.

Rick

 

[davg]

Dude... MBP & MBA are not compatible!!!!! I can't see the burnt item, but I would be thinking of a) finding out what that is and b) replacing that first. Google for your schematics and board view files. If you want to take a closer pic of the burnt bit I will try and identify the item for you.

Rick

Ya when the two connectors looked alike I though it might work?? I will try to get a closeup when I get some daylight in the meantime I have circled the area in question, don't know if you can see it any better?? Don't look like there are any components. Ya I did get some smoke in this area may have ruined the chance for a repair?? The computer still work fine though just have to use external monitor.

 

[Rickkap]

Ya when the two connectors looked alike I though it might work?? I will try to get a closeup when I get some daylight in the meantime I have circled the area in question, don't know if you can see it any better?? Don't look like there are any components. Ya I did get some smoke in this area may have ruined the chance for a repair?? The computer still work fine though just have to use external monitor.

Sorry can't see the photo that well and without boardview it's hard to know what's in this area. Have you check to see if you have a short??

If not try this, take the battery off and disconnect from the magsafe then put your multimeter in diode mode, put the red probe on ground and put the black probe on pin 3 or 4 of the LVDS connecter and tell me what you have?

Also whilst in diode mode do both sides of the fuse and tell me what you have?

Rick

 

[davg]

Sorry can't see the photo that well and without boardview it's hard to know what's in this area. Have you check to see if you have a short??

If not try this, take the battery off and disconnect from the magsafe then put your multimeter in diode mode, put the red probe on ground and put the black probe on pin 3 or 4 of the LVDS connecter and tell me what you have?

Also whilst in diode mode do both sides of the fuse and tell me what you have?

Rick

Here are a couple of close-up. pin 3 or 4 is OL measuring as suggested (not sure where 1 is I assumed as per the photo) Measuring on both sides of the fuse I read .427 V either side.