Magsafe Mystery

Discussion in 'MacBook Pro' started by grantza, Jun 9, 2014.

  1. grantza macrumors newbie

    Joined:
    Jun 9, 2014
    Location:
    Cape Town
    #1
    I lent an old MBP (15") to a friend. (MBP 3.1)
    Somehow, she managed to damage / destroy the Magsafe adaptor.

    I realized I had a cable with a Magsafe adapter still on it from an old 13" MacBook (the power unit packed up - so i nipped the cable off it before chucking it out).

    I replace the now crushed MagSafe adaptor with the "good" adaptor from the old 13" MacBook's power supply (so now the old MagSafe adapter from the 13" MB is connected to the 85w power supply for the 15" MBP)

    Green LED comes on - but no power.
    Remove battery & power - do SMC reset - still just green LED & no power.

    Remove battery & power, SMC reset again, but this time keep holding the power button down as I connect the MagSafe adapter - continue to hold for a further 5 secs, release power button, & press power button again.
    Machine starts up.

    However, the fans are flying at full speed & keyboard backlight does not work.
    Shutdown, restart & do PRAM reset (3 loops).
    Machine restarts - fans still at full speed. (all other functions are perfect).

    Is there an incompatibility issue with the MagSafe adapter that came with the power supply units (60w or something) & the MBP's 85w power supply.
    I do know the centre pin on the MagSafe adaptor carries certain info between the power supply unit & the machine itself.

    ***Note***
    A friend has the same spec machine as the one in question here, manufactured about 3 months apart.
    My power supply (with the newly attached magsafe adapter) starts his MBP perfectly.
    His power supply starts my MBP perfectly (as it usually should).
    This to me, seems to eliminate a problem on the logic board

    Any ideas ?
     
  2. laurihoefs macrumors 6502a

    laurihoefs

    Joined:
    Mar 1, 2013
    #2
    The MagSafe connector includes a chip, that stores some information about the charger (power rating, ID, revision, family, serial number, etc.), and after reading this information the SMC negotiates a connection with the charger. The problem could be, that the old MBP does not recognize the charger with its newer family number as a genuine charger, while a slightly newer MBP recognizes it.

    There's an Apple support article about some compatibility issues with 2007-2008 MacBook Pro's, see http://support.apple.com/kb/TS3499

    If this is what's going on in your case, there's a firmware update available that could possibly fix the issue. But you might need OS X 10.5 or 10.6 to install it: http://support.apple.com/kb/DL1312
     
  3. grantza thread starter macrumors newbie

    Joined:
    Jun 9, 2014
    Location:
    Cape Town
    #3
    Appears the MBP already has the latest firmware available (SMC Version (system): 1.16f11)
     
  4. laurihoefs macrumors 6502a

    laurihoefs

    Joined:
    Mar 1, 2013
    #4
    Did the firmware updater exit with 'No update needed'?

    According to http://support.apple.com/kb/ht1237 1.16f11 is SMC firmware version 1.3, perhaps 1.4 was only distributed as a separate download?
     
  5. grantza thread starter macrumors newbie

    Joined:
    Jun 9, 2014
    Location:
    Cape Town
    #5

    states:
    Alert
    This computer does not need this update
     
  6. laurihoefs macrumors 6502a

    laurihoefs

    Joined:
    Mar 1, 2013
    #6
    Is any adapter info visible in System Information > Power > AC Chargers when it's plugged in? What does it say?

    Also check that your battery condition is 'Normal'.
     
  7. jruschme macrumors 6502

    jruschme

    Joined:
    Dec 20, 2011
    Location:
    Brick, NJ
    #7
    The "intelligence" of the MagSafe adapter is in the plug. So, basically, you have an 85 watt adapter which identifies itself as a 65 watt adapter.

    Could it be that the MBP is ignoring the adapter because it thinks it's too small? It definately won't run and charge the battery simultaneously in that configuration.
     
  8. TheIguana macrumors 6502a

    TheIguana

    Joined:
    Sep 26, 2004
    Location:
    Canada
  9. grantza thread starter macrumors newbie

    Joined:
    Jun 9, 2014
    Location:
    Cape Town
    #9

    this is what i also initially thought, however, it powers up & charges a friend's identical model / spec MBP
     
  10. Altemose macrumors G3

    Altemose

    Joined:
    Mar 26, 2013
    Location:
    Elkton, Maryland
    #10
    The 13" models use the 60 watt adapter. Since the internal chip is in the head of the MagSafe itself, and not in the brick you essentially put a Chihuahua's head on a Great Dane.

    Since the other adapter works fine, I recommend buying a new adapter. You may be able to get lightly used adapters from eBay or shopgoodwill.com.
     
  11. thekb macrumors 6502a

    Joined:
    May 8, 2010
    #11

    Yes. Trade power adapters.
     
  12. JustinePaula macrumors regular

    Joined:
    Mar 14, 2012
    #12
    "put a Chihuahua's head on a Great Dane."

    The mental picture....thanks for the laugh...OMG
     
  13. grantza thread starter macrumors newbie

    Joined:
    Jun 9, 2014
    Location:
    Cape Town
    #13
    I chuckled as well.
    Had a vision of a scene in the movie Mars Attacks.
     
  14. Altemose macrumors G3

    Altemose

    Joined:
    Mar 26, 2013
    Location:
    Elkton, Maryland
    #14
    Your welcome. I laughed thinking of how to write it.

    You can get a gently used or new MagSafe on eBay or Amazon for not much dough in comparison to using your "mutt" charger. I'd recommend doing that.
     
  15. grantza thread starter macrumors newbie

    Joined:
    Jun 9, 2014
    Location:
    Cape Town
    #15
    It's for an old spare MBP, so I am in no rush - was more curious as to what was going on with the MagSafe adaptors.
    I'll be in London for a few days next week, will pick one up there.

    Here in South Africa you get screwed over so badly by the Apple distributor - they do not even bother to offer a dab of KY to ease the pain !
     
  16. laurihoefs macrumors 6502a

    laurihoefs

    Joined:
    Mar 1, 2013
    #16
    I'm still quite intrigued by this, and have been thinking what could explain this behaviour.

    All the logic is in the connector. So it should not matter what's at the other end of the power cord, as long as it supplies the correct voltage. But that's the one key difference between the 85W and 60 W chargers: the 85 W charger provides 18,5 V, while the 60 W one provides 16,5 V. So maybe this is about component tolerances.

    If the SMC detects the charger as a 60 W version, it's going to expect a voltage close to 16,5 V. Your power supply should provide 18,5 V, but due to component tolerances, the real output may be a bit lower or higher, and might fluctuate. So maybe it just happens, that your charger is on the high side.

    Then there's the power-in board, which has voltage and current sensing circuitry. Maybe it also happens to detect the voltage as slightly higher than it actually is. Combine this with the higher-than-expected voltage, and the power-in board might detect it as a fault, and prevent charging.

    If the other computer happens to have components from the other end of the tolerance scale, it might not detect the over-voltage, and allow charging, despite the voltage being on the high side.

    Well, maybe someone can come up with a better explanation, that's all I can come up with :D
     
  17. Altemose macrumors G3

    Altemose

    Joined:
    Mar 26, 2013
    Location:
    Elkton, Maryland
    #17
    I am not aware of the differences but your answer definitely makes sense! In simple terms, the OP has to get rid of the mutt of a charger.
     
  18. laurihoefs macrumors 6502a

    laurihoefs

    Joined:
    Mar 1, 2013
    #18
    That pretty much sums it up :D
     
  19. grantza thread starter macrumors newbie

    Joined:
    Jun 9, 2014
    Location:
    Cape Town
    #19
    I too am intrigued.
    The other MBP that the charger / MagSafe works on has a manufacture date 3 months apart (earlier).
    There are 2 other small differences:
    My MBP has 4GB RAM - the other has the standard 2GB.
    My MBP has a 320GB 7200rpm HD - the other has the standard 160GB @ 5400rpm.
    Otherwise identical.
     
  20. Altemose macrumors G3

    Altemose

    Joined:
    Mar 26, 2013
    Location:
    Elkton, Maryland
    #20
    I would just get a new MagSafe adapter to be honest with you.
     
  21. grantza thread starter macrumors newbie

    Joined:
    Jun 9, 2014
    Location:
    Cape Town
    #21
    Sure.
    As I stated earlier, I'll pick one up in London next week.

    However, the mystery remains !
     
  22. Altemose macrumors G3

    Altemose

    Joined:
    Mar 26, 2013
    Location:
    Elkton, Maryland
    #22
    Let's get Scooby Doo to investigate the mutt of a MagSafe. Good luck with the new adapter.
     

Share This Page