Identifying fuse on A1278 (mid 2010 13" MBP) Logic Board

Discussion in 'MacBook Pro' started by ek13, Oct 18, 2012.

  1. ek13, Oct 18, 2012
    Last edited: Oct 18, 2012

    macrumors newbie

    Joined:
    Nov 5, 2011
    #1
    Hello,

    Can anyone help identify the fuse circled yellow in the picture below? I am trying to diagnose the logic board and am not getting any resistance or continuity on that particular fuse.


    It's a mid 2010 13" macbook pro (A1278) unibody I bought that had a spill. First time I connected it booted up and was working but very slow and battery was not charging. Now it's dead and I'm trying to diagnose it.

    • Magsafe connector is dim pulsating green
    • Magsafe adapter is 85W and good since it works another Macbook
    • tried reset SMC
    • disassembled and cleaned logic board using 99% Isopropyl Alcohol
    • tested resistance on all white fuses - ok
    • tested voltage on all white fuses (18.8v by DCIN connector and 0.8v close to battery connector)
    • tested continuity on logic board and DC IN board - ok
    • ordered a new DC IN board, hoping that's the cause.

    Any help would be great.
     

    Attached Files:

  2. zamirow, Dec 1, 2012
    Last edited: Dec 1, 2012

    macrumors newbie

    Joined:
    Dec 1, 2012
    #2
    Exactly the same Problem....

    Hi ek13,

    I have the same problem on my MacBook A1278 and my logic board is : 820-2327A 2008, and the Magsafe connector is dim pulsating green and nothing else...

    I don't no what is the "yellow fuse" but Now I’m searching for a " MacBook 13″ Unibody A1278 schematic,SCHEM,MLB,M97 " but I didn't find it for the moment. It could help us to find what this component is!!

    I made a test and shunted the Yellow fuse and pushed the power button but nothing...

    I found the different tension than you, ~16v by DCIN connector and tomorrow I go to take on more time the tension on the DCIN and the tension near the battery connector.

    Can you tell me when you receive your DC IN Board please :)!!

    I continue to make some test and I tell you if something new!!

    And if someone know this problem , please can tell us what are in default, it would be really nice :)

    Thanks a lot

    Ps : Sorry for my bad english....

    Zamirow
     
  3. thread starter macrumors newbie

    Joined:
    Nov 5, 2011
    #3
    HI Zamirow,

    I ordered another DCIN board from ebay and tried it but that didn't solve the problem.

    You are likely getting ~16V at the DCIN board because you are using a 65W power adapter (mine is a 85W and hence, 18.5V). Chances are your DCIN board is fine.

    I'm stuck right now with what else I can do to diagnosis the exact problem. I would like to find out what the readings on all the components should be also so I can figure out where the problem lies.

    there is a long and informative thread that I've been following for help. Maybe it will be help to you:
    http://forums.macrumors.com/showthread.php?t=1122338

    ----------

    here is the way to measure and test your DCIN board:

    http://forums.macrumors.com/showpost.php?p=16343697&postcount=1106
     
  4. zamirow, Dec 1, 2012
    Last edited: Dec 1, 2012

    macrumors newbie

    Joined:
    Dec 1, 2012
    #4
    Solution for us !! :)

    Sorry I haven't seen your message !!

    Yeahh my MB have resurrected !!

    Thankss
     
  5. thread starter macrumors newbie

    Joined:
    Nov 5, 2011
    #5
    That's great! Can you tell me what it was or what you did? The link your provided is for the entire thread.
     
  6. zamirow, Dec 1, 2012
    Last edited: Dec 1, 2012

    macrumors newbie

    Joined:
    Dec 1, 2012
    #6
    The procedure is : ( it's Temporaly procedure okay ?)

    - With the magsafe disconnected press and hold the power button.
    - While continuing to hold the power button plug in the magsafe connector.
    - Continue to hold down the power button for 5 to 10 seconds.
    - Release the power button and wait a couple of seconds.
    - Now press and release power button. PRESTO!

    Whole thread here : http://forums.macrumors.com/showthread.php?t=1122338

    Thanks to my new God of the electronic: Dadioh ;)

    Z

    ----------


    So now we know the SMC control circuit are in failure !! Also this method doesn't allow the mac to charge the battery!!

    ----------

    Don't forget to put the RAM and the HDD !! and normaly the MB boot up and work fine !! :)
     
  7. thread starter macrumors newbie

    Joined:
    Nov 5, 2011
    #7
    That's one of the first things I tried too but my issue wasn't with SMC. I'll will update this post if I ever fix the issue. At least, you have your macbook back!
     
  8. macrumors newbie

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    Dec 1, 2012
  9. macrumors newbie

    Joined:
    Dec 2, 2012
    #9
    The component in the circle looks more like a ceramic capacitor in a 1206 package. If you are looking for a fuse, then look below the display connector in the picture, at the same height as the second connector on the right. A green component with the text "24 V", which is a thermally tripped resettable fuse.

    From the picture it seems more likely that the black component on the upper left of the yellow circle is a part of the problem. That could a MOSFET and part of an input protection/regulation.
     
  10. macrumors newbie

    zixu

    Joined:
    Feb 1, 2013
    #10
    Just passing A1278 schematic is here. http://podnutz.com/forums/download/file.php?id=638&sid=06fca7dd7a4b0c6b689a743d19e65fe3
     
  11. macrumors newbie

    Joined:
    Dec 1, 2012
    #11
    Thankss but now I'm using my MB with a Full Fan Noise for the moment....

    ----------

    Hey, I found something interesting :) For our dead MB :) ( Service Manual)

    http://tim.id.au/laptops/apple/macbook/mb13_al_late08.pdf
     
  12. macrumors newbie

    Joined:
    Dec 1, 2012
    #12
    Hey ek13,

    it's a picture of your Logic Board in the beginning of the thread ??

    Because as Nickepicke said : " From the picture it seems more likely that the black component on the upper left of the yellow circle is a part of the problem. That could a MOSFET and part of an input protection/regulation. "

    And in your picture I see the Mosfet with only 3 pins.... :eek:

    On my Logic Board I have 4 pins for the regulator :)
     
  13. macrumors newbie

    Chipmaster

    Joined:
    May 18, 2013
    #13
    Schematic Anyone?

    Well if you didn't fix it, here is the file for it.
     

    Attached Files:

  14. thread starter macrumors newbie

    Joined:
    Nov 5, 2011
    #14
    Thank you Chipmaster, zamirow and zixu for the service manuals and schematics.

    I had put off trying to diagnose the laptop after come up with no answers and didn't want to spend upwards of $250 on getting it repaired.

    zamirow, I too noticed the the mosfet with the 3 pins after I initially cleaned the board. It looks connected but the soldering has come off. I was thinking of seeking out the specific mosfet, purchasing it online and taking to a circuit board repair shop to have it installed. Since I don't know what else to try, I figure it's worth a shot. I will post any findings or progress.
     

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