Macbook pro A1286 fixed fuse for LED backlight and screen flashes and turns off

Discussion in 'MacBook Pro' started by m00nman, Feb 5, 2012.

  1. m00nman macrumors newbie

    Joined:
    Feb 5, 2012
    Location:
    Canada
    #1
    Hello everybody,

    I have a problem with my macbook pro. I got it used and I have no idea what happened to it before. The screen did not work and after reading the forums here I decided to take it apart and find the fuse for LED backlight. I found it, and I just shorted the pins of the fuse and everything seemed to work just fine, however after 10 min the screen started flashing and then turned off. I have a video here: http://youtu.be/LKam1Zd0RRc start watching at about 2:30
    I did reset the PRAM and SMC. External monitor works, and everything else in the computer works just fine.

    Where should I look and what could be worng?
     
  2. pscraig, Feb 5, 2012
    Last edited: Feb 5, 2012

    pscraig macrumors member

    Joined:
    Apr 9, 2008
    #2
    Was it the white rectangular SMT device? Well, that wasn't a fuse, it is a capacitor for the LED drive circuitry. The LEDs in the backlight and possibly the rest of the drive circuitry is likely toast. Possibly a new display assembly, or possibly more.

    Honestly I'd send this one in to someone like Powerbook Medic who have the proper diagnostic tools and parts inventory to fix it. You might just need a new display assembly, or there may be more damage, such as to the voltage regulators on the logic board. The displays on the unibodies are very hard to disassemble, lots of glue and a heat gun is required. Most repair shops just change out the display assembly as a complete unit (top case, LCD panel, bezel, iSight, mic, etc). The labor costs make it pointless to disassemble the unibody displays just to swap out a panel.
     
  3. m00nman, Feb 5, 2012
    Last edited: Feb 5, 2012

    m00nman thread starter macrumors newbie

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    #3
    Hi, thanks for your reply.

    No it wasn't the white one, it was a very little rectangular piece with a yellow dot on it. Since the fuse is just basically a conductor I thought I would just connect the two sides with a solder... I'll post some pics

    EDIT: Here are the pictures

    [​IMG]

    [​IMG]
     
  4. marc11 macrumors 68000

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    Mar 30, 2011
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    NY USA
    #4
    A fuse is much more than just a conductor it is a safety device designed and implemented to protect more valuable things downstream from it. Be it boards, screens or humans. If it was a fuse you bypassed then that fuse blew for a reason and you basically let that unsafe condition travel to places and potentially damage things that the fuse was designed to protect.

    Based on that fact that you thought it would be a good idea to just solder the fused link together I suggest you save the rest of the pc from yourself and have a professional look at and repair it.
     
  5. m00nman thread starter macrumors newbie

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    #5
    I do appreciate your help guys, but let me explain. I either fix it myself or i just let it be. I dont want to spend hundreds of bucks on fixing it. I know what a fuse is and what it does, but it looks like the laptop had something spilled on which blew the fuse, if nothing like this happens again then i have nothing to worry about. I am just looking for a quick and rough fix, and not necesserely looking to do things "properly". If it blows then it blows, if i fix it then awesome. Of course i would rather have it fixed, but you know what i mean... :)
     
  6. pscraig macrumors member

    Joined:
    Apr 9, 2008
    #6
    This isn't just a fuse box on a house. By jumping over the fuse (or could be a resistor, hard to tell) you removed protections from more sensitive components down stream from the driver circuitry.

    There's really no quick and rough way to fix this. It's not like shorting out something in a car to make a bulb come on-LEDs are very sensitive devices designed to operate in a given voltage envelope, but more importantly within a certain current envelope. Something is wrong somewhere-some component failed, caused a short, drew too much current, and caused the protection circuitry to activate. Your backlight in the video is exactly what it looks like when you connect an LED directly to a battery and allow it to fry itself, with nothing to limit the current.

    As I said you could try connecting a new display assembly (~$300-400) but I am reasonably certain that the backlight LEDs and/or the drive circuit is completely toast. You no longer have functioning backlight LEDs.
     
  7. m00nman, Feb 6, 2012
    Last edited: Feb 6, 2012

    m00nman thread starter macrumors newbie

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    #7
    Well, if i let the computer to "cool down", its backlight turns on again. That's how i was able to record the video. And it wasn't the resistor, for sure. I measured the impedance and it was infinity. I know for sure it was the fuse.
     
  8. Dadioh macrumors 65816

    Dadioh

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    Canada Eh?
    #8
    Sounds like something is overheating. My guess would be the WLED driver chip. On the A1286 I believe that is a custom device for Apple codenamed GOSHAWK and labeled APP-001 on the top. Is it possible that the part was replaced by someone? If so, it is tricky business resoldering the device to make sure that the thermal pad underneath the chip is soldered first before soldering the rest of the pins on the QFN package. If that pad is improperly soldered then really good chance it will overheat.

    Getting a replacement WLED driver entails finding a donor board and moving it over to your board. Requires highly technical soldering skills.

    Is the WLED driver on the bottom of the board so you have access to it while running? If so, you could try to touch it with your finger to see if it is radically overheating. If you can't hold your finger on it then the rule of thumb is that it is greater than 60C. Probably too hot.

    Good luck.
     
  9. m00nman thread starter macrumors newbie

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    Canada
    #9
    Hi Dadioh, I appreciate you replying. No I had the computer running till the screen shut off and had my finger on the chip. It did not overheat.
    The chip is VM04AF L8543SQ where Q is a letter q or a number 0 or maybe an o. It's hard to see. There are 2 rectangular pieces, 1 on each side of the chip and they are both not soldered straight for some reason.
     
  10. Dadioh macrumors 65816

    Dadioh

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    Canada Eh?
    #10
    OK. That is good news in one sense. You can purchase the LP8543 from Newark or Digikey. I don't know for sure but what you are describing sounds like that device is misbehaving. Replacing it does require fine soldering skills and equipment. You might try to see if you can find someone local with the ability to replace it.
     
  11. Mori3000 macrumors member

    Joined:
    Mar 13, 2012
    #11
    Hi Dadioh

    I have just read your information about this driver, I have some macbook and macbook pro which have problem with this driver but i do not know which ic is the right LCD driver and where to buy it from.

    Do you know any where which i can buy this driver?

    Thanks
     
  12. Dadioh macrumors 65816

    Dadioh

    Joined:
    Feb 3, 2010
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    Canada Eh?
    #12
    I have another thread covering backlight issues and loaded with photos and info on this driver. If you search my posts you will find it. Pretty sure the info you need will be in there.
     
  13. Ccrew macrumors 68020

    Joined:
    Feb 28, 2011
    #13
    Umm, just an FYI. Resistors normally fail open.
     
  14. l.a.rossmann, Apr 26, 2012
    Last edited: Apr 26, 2012

    l.a.rossmann macrumors 65816

    l.a.rossmann

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    Location:
    Brooklyn
    #14
    If it wouldn't lose me a lot of LCD wholesale business, I'd love to tell you how many professional shops that claim to do board level repair solder over the fuse. If only you knew. lol. Some of the biggest reverse logistics providers in the country that large shops send their customer's boards to do this as common practice. I really thought this was limited to my live sound experience during my teenage years where the FOH guy would wrap the fuses of the amplifiers with tin foil from his lunch sandwich if they blew mid show, but this crap happens all the way up the ladder.

    3 and a half years ago before I had a clue I'd use a featherweight wire, something even skinnier than a strand of wire in an IDE cable, after removing the fuse. I lacked the equipment to do good SMD rework, the best I could do was solder a jumper after removing the old fuse. I doubt this was any better. Soldering over the fuse seemed too ghetto, the ball would have to be large and heavy to go over the fuse. It could fall off at any time. I couldn't bring myself to solder over a fuse. Not that this is any less ghetto than putting a strand of ultra high gauge wire between the pads.

    Now, I look for the value of the fuse, and replace it with a proper fuse. It's hard to find people who care about basic workmanship. People who care if someone sees what they did 30 years later. Unfortunately, most just don't care. Patch it up with the least amount of work, skills, or equipment necessary, and be on their way. The people who don't care will likely be onto their next job by the time their work blows up in someone's face, and it won't be their problem.

    Sorry I didn't have anything useful to contribute. Except, on an Apple board(or any modern board), don't assume something is a fuse, capacitor, or resistor based on the color of the head of the device.. you will end up frying something. Been there, done that.

    ----------

    I've had the privilege of selling parts to some young entrepreneurs who charge $25 to swap out the panel, who don't break the glass, and don't get dust under the glass.
     
  15. willko macrumors newbie

    Joined:
    Aug 29, 2012
    #15
    Any idea where to get that fuse?

    Hi, I have the same MBP ( A1286 - 2009, Logic Board 820-2533-B) and I have the same problem... No backlight, external monitor wroks fine and I have 2 lids that both work that behave the same way when connected to this MBP but work fine on other MBPs...

    Anyway, just wondering if you identifies this fuse and found a source for it? Sounds like replacing this might just do the trick - if not I guess I'll be sending to an expert for the driver replacement.

    Any thoughts anyone?

    THANKS!
     
  16. mac-n-sauce macrumors regular

    Joined:
    Jun 25, 2012
    Location:
    Tampa, Fl
    #16
    You have to know why the fuse blew. If you replace the fuse without fixing the problem it will blow again. The fuse is on the top of the board. You will have to remove the logic board to get to it. I have attached photos for you to dee it of your very board. It is located an inch east of the dc jack, .75 inches south of the edge of the board.
    It is a 2amp - 32v fuse in a 402 package. It can be purchased at digikey.com
    Their part number is P15123CT-ND
    Buy 10 they are cheap. You will loose one or two because they are so small.

    I use my hot air station without the fan on and sewing needle in an alligator clip to move it gently into place and then to hold it there. If you use liquid flux be careful because when it heats it boils and throws the fuse somewhere. Not sure where, still can not find it! :)

    Just sharing some of my rookie mistakes. Anyway, you might want to order the LP8543SQX while you are at Digikey because chances are you will need it.
     

    Attached Files:

  17. willko macrumors newbie

    Joined:
    Aug 29, 2012
    #17
    Thanks!


    Thank you very much for your kind help!! Much appreciated! I have ordered the fuse ( x10 :) ) and the WLED.... I'll let you know how I get on OR when when I get stuck, most likely LOL!... I''m busy reading all forum posts on the subject of 0402 work and replacing WLEDs so I don't ask any "dumb" questions...

    Again, thank you for your time, help and great advice!
     
  18. willko, Oct 22, 2012
    Last edited: Oct 23, 2012

    willko macrumors newbie

    Joined:
    Aug 29, 2012
    #18
    Some advice pls

    Hi all,

    Quick question,.. Is it possible for a faulty Magsafe to cause the 2A fuse to blow? I've replaced the fuse twice now, both times the the resistance is 0 and connections good, then when I assemble the board with magsafe and apply power, no backlight - when I test the fuse again it is blown...

    Any links or advice on how to check if the magsafe connector is functioning correctly?

    It is part number 820-2565-A

    Many thanks!

    edit: sorry, should have mentioned - this has happened on 2 different boards (both 820-2533-B), one of which I know the WLED is good and was working fine before I tried it with the macbook I'm trying to repair... ( so, yes, I borrowed my brothers perfectly good macbook, same model, and blew the fuse - he was very grateful :) ) I'm pretty sure the target board's WLED is good too, I've got readings that agree with posted measurements indicating all OK... The magasafe is the common denominator in the failures,.. Any idea how I measure the outputs to make sure it is OK/faulty...
     
  19. Fabbry macrumors newbie

    Joined:
    Apr 4, 2013
    #19

    Hi Willko, i'm into same situation of your mac, same mb , same water damage..same broken pins... on lvds connector....i am interested in knowing if u have been able to solve all problems...and if you have some things to share before i start trying fixing by myself.
    Thank You
     
  20. yaman macrumors newbie

    Joined:
    Dec 1, 2011
    #20


    You are a legend, just ordered the fuse from digikey now !
    thank you
     
  21. mac-n-sauce macrumors regular

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    Jun 25, 2012
    Location:
    Tampa, Fl
    #21
    Did your lvds connector get any damage to the pins? Do you have the schematic for the board? There are several parts in the circuit that can get damaged.
    The dc-in(magsafe board) puts out 16 - 18v but i am guessing this is not the problem
     
  22. cpufixer, Apr 17, 2014
    Last edited: May 8, 2014

    cpufixer macrumors member

    Joined:
    Apr 2, 2014
    #22
    digikey does not have the LP8543SQX any more, what did you order instead?

    EDIT: I asked one of the guys at digikey, and came up with same number plus extension...
     

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