MacBook Pro Unibody - No Backlight - Logic Board Question

[jcorvera]

Dadioh, I need your help. I have a Macbook Pro 2010 w/ a 820-2850 A logic board. I dont have backlight, then I followed the steps to see the fuse, and the fuse has continuity but the 638Z components, between the legs you mention, dont have 300 ohms, they read 0. I double checked all the information and the readings from the multimeter.

What I'm suppouse to do? Another check?

 

[Dadioh]

Dadioh, I need your help. I have a Macbook Pro 2010 w/ a 820-2850 A logic board. I dont have backlight, then I followed the steps to see the fuse, and the fuse has continuity but the 638Z components, between the legs you mention, dont have 300 ohms, they read 0. I double checked all the information and the readings from the multimeter.

What I'm suppouse to do? Another check?

Make sure you are measuring between pins 3 and 4. That would be the 300kohm (Note kilo-ohms not ohms) resistor. Pins 1, 2, 5, 6 are all shorted together so if you are at the wrong end of the 638 you could be measuring pins 1 and 6.

If you are indeed measuring 0 ohms between 3 and 4 then R9808 300kohm is shorted out. Could be the resistor or could be the FET (638Z).

 

[jcorvera]

Thanks for reply Dadioh!..

Ok, yes, I missunderstand the 300 ohms... yes, it has 300k ohms and the fuse has continuity, what can be?

Thanks again! =)

Make sure you are measuring between pins 3 and 4. That would be the 300kohm (Note kilo-ohms not ohms) resistor. Pins 1, 2, 5, 6 are all shorted together so if you are at the wrong end of the 638 you could be measuring pins 1 and 6.

If you are indeed measuring 0 ohms between 3 and 4 then R9808 300kohm is shorted out. Could be the resistor or could be the FET (638Z).

 

[ERRDivideByZero]

Yet another Update...

Okay, so after doing some more digging on the web... and staring at the schematics until my eyes watered, I checked the voltage on PPVOUT_S0_LCDBKLT on the LVDS Connection (Pins 38,39 and 40). I'm getting 3.2V... That being said, I'm not using a TrueRMS Meter, and I may just hook up my scope to see if there's anything weird or inaccurate about my readings... but what should the voltage be?

And yes, I will be purchasing a TrueRMS meter.

 

[ERRDivideByZero]

So, after some investigation, it turns out that some of my measurements may be incorrect (voltage measurements). As a lot of this is PWM, and I don't have a RMS meter... I may have been overlooking some important details. Either way, I'm going to be going through my measurements for all of the board and things I have taken thus far with my trusty ol' scope and verify everything.

 

[udawat]

It is odd that PPVOUT_S0_LCDBKLT is 3.3V. In non-boosted state it should be 12V. The WLED driver then boosts it up to 30ish Volts. Sounds like the WLED driver is bad. Do you get 12V leading into WLED circuit from the fuse through the FET?

My last measurement of PPVOUT_S0_LCDBKLT was incorrect. It is indeed 29.6 V when i turn ON the Backlight from F2 key. When i go all the way down to turn off the backlight using F1 key, the reading is 11.5 V.

Also, i measured the voltage after fuse, PPBUS_S0_LCDBKLT_PWR to be ~ 11.9 V. Thus, confirming your other statement.

I can adjust the backlight using keyboard keys, but there is no video. I really appreciate your troubleshooting tips.

 

[Dadioh]

My last measurement of PPVOUT_S0_LCDBKLT was incorrect. It is indeed 29.6 V when i turn ON the Backlight from F2 key. When i go all the way down to turn off the backlight using F1 key, the reading is 11.5 V.

Also, i measured the voltage after fuse, PPBUS_S0_LCDBKLT_PWR to be ~ 11.9 V. Thus, confirming your other statement.

I can adjust the backlight using keyboard keys, but there is no video. I really appreciate your troubleshooting tips.

So the backlight is on but no video? Just a white screen? Does it display video on external monitor?

Check presence of 3.4V on PP3V3_SW_LCD and PP3V3_S0_DDC_LCD. Also check the LVDS connector pins to see if any damaged pins. Remove the cable and look into the interior of the connector with a microscope. I hold the board on edge below the microscope to do that.

 

[udawat]

So the backlight is on but no video? Just a white screen? Does it display video on external monitor?

Check presence of 3.4V on PP3V3_SW_LCD and PP3V3_S0_DDC_LCD. Also check the LVDS connector pins to see if any damaged pins. Remove the cable and look into the interior of the connector with a microscope. I hold the board on edge below the microscope to do that.

Yes, backlight works but there is no video on screen. I can see bright LEDs glowing behind the LCD panel. External Monitor works fine without any difficulties using a mini Display Port to VGA adapter.

I could not find PP3V3_SW_LCD and PP3V3_S0_DDC_LCD in the schematic/board files. If you mean the 3.3 V power supply signals for the LVDS Connector, then yes, i have measured PP3V3_S0_LCD_F to be 3.47 V and PP3V3_LCDVDD_SW_F to be 3.49 V using an oscilloscope (LVDS Pins 2, 3 and 4). [Schematic reference attached.]

 

[edgardoiracheta]

smc chip problem

I did a smc bypass and it worked a few days until I left it overnight. doesn't want to boot up. The logic board is 820-2330-a, if anyone can help on measuring the power rails or were should I start I would apperciate it.

-Thanks

Image
Image

hi dude do you fix your computer i have the same problem here, and i can't find information for this motherboard, my computer turn on only resetting the smc, holding 10 sec. but the battery it's dead and the magsafe doesn't show any light at all, the keyboard light the same without power, i hope you can help me please.

 

[l.a.rossmann]

I have tried to help a little but this is impossible. Doing this all in one thread is a nightmare. There are 90 people all screaming different questions at the same time, I get a headache trying to read back through each individual case.

advancedreworks.com has a forum on which I am a regular. I post a reply to every thread in the mac section. I don't answer PMs because this helps no one but the reader of the PM, and I can't answer here because reading the history of each specific case is a nightmare.

It is a free forum to join and I am happy to help anyone on it. I usually post around 1 to 3 AM since this is the only time of day I have free. I have solved many people's problems in the few weeks I have been a regular.

A second alternative I can find would be a subforum on this website for macbook logic board repair related issues. I would be happy to reply to each thread on a per-issue basis and help people with their issues, so long as they follow some basic rules(have a schematic handy and use your brain when I give advice). I would not ask money for this.

This way you have a database of issues you can search through, and each issue has its own thread, so it is actually helpful. While all of the advice here is great, it's 74+ pages of clooged together scattered information. This is confusing to the end user.

I'm good at this, and I will fix a lot of these for people who have the time & determination to follow the hints I provide.

Thoughts?

 

[ERRDivideByZero]

Readability

I have tried to help a little but this is impossible. Doing this all in one thread is a nightmare. There are 90 people all screaming different questions at the same time, I get a headache trying to read back through each individual case.

advancedreworks.com has a forum on which I am a regular. I post a reply to every thread in the mac section. I don't answer PMs because this helps no one but the reader of the PM, and I can't answer here because reading the history of each specific case is a nightmare.

It is a free forum to join and I am happy to help anyone on it. I usually post around 1 to 3 AM since this is the only time of day I have free. I have solved many people's problems in the few weeks I have been a regular.

A second alternative I can find would be a subforum on this website for macbook logic board repair related issues. I would be happy to reply to each thread on a per-issue basis and help people with their issues, so long as they follow some basic rules(have a schematic handy and use your brain when I give advice). I would not ask money for this.

This way you have a database of issues you can search through, and each issue has its own thread, so it is actually helpful. While all of the advice here is great, it's 74+ pages of clooged together scattered information. This is confusing to the end user.

I'm good at this, and I will fix a lot of these for people who have the time & determination to follow the hints I provide.

Thoughts?

I'm all for it either way, and this has been pretty tedious to go to, as each of us have the same problem, with different boards. Some of the info matches, some doesn't and I completely agree that this should be made more readable. I checked out the site you mentioned, its nice, but going through the "Blog" section, there isn't already a mac section, or if there is, I was unable to find it by searching the site (with google and its own search function). If we were to make a section here, I think it would definitely be a good start, maybe setup a hierarchy like:

Backlight issues
-> Logic Board repair
-->[BOARD NUMBER]

And the first post would be common things to check (IE the fuse, LVDS cable, etc), with maybe a link to the schematic and boardview file (and reader if necessary).

I would be up for this completely, and I would also be more than happy to donate the schematic that I paid for and the board view files I have.

Great suggestion!

EDIT: I would also be up for assisting in the setup of the hierarchy and combing through posts here to get all of the currently posted board numbers. Granted, I'm no admin, but once those are setup, I see no reason for an admin not to move them to the correct section. (if possible)

 

[Dadioh]

I have tried to help a little but this is impossible. Doing this all in one thread is a nightmare. There are 90 people all screaming different questions at the same time, I get a headache trying to read back through each individual case.

.
.
.

Thoughts?

I agree. I really don't have the time necessary to sort through each history. I kick in advice once in a while when I have a few minutes but really hit and miss. A thread for each problem is a far more useful format.

Thanks Louis. You have been really generous with your time. Very helpful.

 

[l.a.rossmann]

I'm all for it either way, and this has been pretty tedious to go to, as each of us have the same problem, with different boards. Some of the info matches, some doesn't and I completely agree that this should be made more readable. I checked out the site you mentioned, its nice, but going through the "Blog" section, there isn't already a mac section, or if there is, I was unable to find it by searching the site (with google and its own search function). If we were to make a section here, I think it would definitely be a good start, maybe setup a hierarchy like:

Backlight issues
-> Logic Board repair
-->[BOARD NUMBER]

And the first post would be common things to check (IE the fuse, LVDS cable, etc), with maybe a link to the schematic and boardview file (and reader if necessary).

I would be up for this completely, and I would also be more than happy to donate the schematic that I paid for and the board view files I have.

Great suggestion!

EDIT: I would also be up for assisting in the setup of the hierarchy and combing through posts here to get all of the currently posted board numbers. Granted, I'm no admin, but once those are setup, I see no reason for an admin not to move them to the correct section. (if possible)

http://advancedreworks.com/forum/forumdisplay.php/mac-computers-motherboard-repair.html

This is where I currently post.

I would be happy to post in a subforum of MacRumors if made available, but anything other than it all being in one thread would suffice.

 

[ERRDivideByZero]

Mirrored Post

To all,

I have mirrored my posts to advanced rework forums.

http://advancedreworks.com/forum/sh...-no-backlight-moving-macrumors-forum-350.html

I have also moved any relevant posts to my own, just to make everyone aware.

Thanks again.

 

[josearanax]

i need the 820-2915-b mainboard schematic

hello, i see that you have the schematic of the mainboard 820-2915-b, i have the macbook pro 1286 15" and i need the schematic please, thanks!!!
is very dificult for me to look for this schematic,

my mail is: josearanax@gmail.com

can you sent to my mail the schematic please? thanks!!!

 

[josemedeiros007]

Thank you MacDaddi for posting the picture of the 2009 15 inch Apple Mac Book Pro A1286 logic board and location of the LCD display backlight fuse.
https://forums.macrumors.com/showthread.php?p=20733501#post20733501

I am hoping that some one on the MacRumor list may know this answer. I have external video through the mini display port connected to my sisters external LCD display, but I do not have video through the Mac Pro's internal LCD display. I bought this Mac Book Pro used on Ebay, it had been dropped with a bent corner, and bent clam shell lid and broken LCD display. I found a good clam shell lid and LCD display locally for a reasonable price and connected the LCD display cable to the logic board with out mounting the hinges to see if it would power on ( My mistake), and got video for a few seconds before I accidentally disconnected the LCD display cable while powered on. I reconnected it, powered it back on, but then had no video.

I am thinking that it's the fuse, but what puzzles me is if the fuse is bad would that still allow the external display port to work? If not, then more then likely it's a bad internal LCD display, or LCD display cable.

I've been unemployed six years from my past job as a Systems Administrator in Information Technology, and do not do component level repair, so money is tight. Thank you for the help in advance, it is very much appreciated.

Regards,
Jose F. Medeiros

 

[Ian.C]

MacBook Pro Unibody - No Backlight - Logic Board Question

Hi

Just wondering if some one can help me .I have a 2012 MacBook Pro retina a1398 with no display at all. When connected to an external displays it works perfectly. I can't find any trace of liquid damage and all sensors are in tact. Please can someone help me with identifying fuses to check thanks Ian

----------

Sorry I forgot to include a picture

Thanks

Ian

 

[l.a.rossmann]

Hi

Just wondering if some one can help me .I have a 2012 MacBook Pro retina a1398 with no display at all. When connected to an external displays it works perfectly. I can't find any trace of liquid damage and all sensors are in tact. Please can someone help me with identifying fuses to check thanks Ian

----------

Image

Sorry I forgot to include a picture

Thanks

Ian

If you have no image, that is a different issue altogether. Check U9000 area. Is voltage gfoing o the chip, is enable voltage there, and is voltage there on output?

 

[Ian.C]

If you have no image, that is a different issue altogether. Check U9000 area. Is voltage gfoing o the chip, is enable voltage there, and is voltage there on output?

Hi Louis,

Thanks alot for the reply..

The model no of the board is 820-3332-A

I have attached an image of the the chips around the wled driver chip and the chip itself. I'm not sure if this is the area i should be looking at.

The only problem i have is a condition that doesn't really lend to steady hands like i use to have and micro soldering wasn't a problem. My brain still love this sort of investigation but parts of my body are no longer capable.

If i need to check the WLED driver chip i will need to find someone in the UK to try and fix this for me as its now beyond my capability unfortunately...

Does anyone know of a really good technician that could possible repair this for me, i have replaced the complete top of the macbook rather than attempt to replace just the screen. I could take it into Apple and ask them but they will probably just replace the whole logic board for £600.

There have never been any liquid near this laptop ever, so hopefully it has a better chance to be repaired...

PS Louis love your videos, especially the last one about health... spot on

Thanks

Ian

 

[l.a.rossmann]

Go to a place called TFix in the UK.

Also, not for you, but with other models, here is a step by step howto for replacing the microbga LP8550 WLED driver.

https://www.youtube.com/watch?v=_KbIw3cwIW4

 

[Nicpoe]

I'm very happy to find this post.

I have a little problem. The backlight on my mac 17" A1297 unibody is faulty. The fuse was blown. I replace the fuse (on backside), but the backlight did not work.

What could be the Problem? Measuring is difficult, it's all on the backside.

Thank you....

 

[kylemcmahon]

macbook pro 2008

hi i have a backlit issue with my brothers mac that i am trying to repair for him im not sure of the exact model of the mac he just told me it is a late 2008

ok so the display works if i shine a torch at the screen or connect to and external display i have dissembled the mac to see if i can see and signs in blow components and cannot see any damage my problem is i cant find the fuse to check that i have good soldering skill so if it is the fuse if should not be a problem i just cannot locate the fuse or components that could be the problem so am hoping you guys can help me out as my brother really need hi s mac for djing am have included pictures of the board to try help out if these ar not clear enough it is no problem to upload clearer ones thanks any info need just ask as im not sure what u guys may need to know also just now after fair bit of time i have found what i think might be the fuse on the other side of the board i have added photo and it is circled with red

thanks in advance

 

[Nicpoe]

i have found what i think might be the fuse on the other side of the board i have added photo and it is circled with red

thanks in advance

exact, this is the backlight smd fuse.

 

[kylemcmahon]

exact, this is the backlight smd fuse.

i have put my multimeter to it and not getting a beep so does that mean it is indeed blown? or should i test other components also iv read alot on the internet people just putting blob of solder to the contacts i dont see how this could be safe or would it be find just to do it to confirm that is all that is wrong then power of machine and get that part and replace

thanks again for fast reply

 

[Nicpoe]

Best idea is to replace it, yes. If you short it, you maybe damage other components.