Can I use this power cord?

Discussion in 'MacBook' started by Fox11, Jan 19, 2010.

  1. Fox11 macrumors member

    Joined:
    Nov 8, 2009
    #1
    I just received an iBook I bought used on eBay (got a great deal, and so far it looks good!). Only problem is- the adapter that came with it is like only 3-4 feet long (the adapter piece JUST reaches the ground from my desk). I plugged in the 'extension' cord from my Macbook Pro's adapter and that seems to be working fine, but now I can only charge my MBP with the little plug thing.

    So my question is this: can I use any power 'extension' cable that fits (i.e. a random black one I just found) to plug the adapter into the wall? Like this:http://www.amazon.com/Universal-Power-Cord-Two-Prong-Misc/dp/B000J0AON4
    It would be great if I could, since this would save me the trouble of switching cords or buying another cord to connect the adapter.
     
  2. TEG macrumors 604

    TEG

    Joined:
    Jan 21, 2002
    Location:
    Langley, Washington
    #2
    Short Answer: Yes. Infact any "Figure-8" AC Cable will work.

    Long Answer: You can use it, but it may be unstable. You may be better off purchasing an Apple Extension Cord, from someplace like e-bay.

    TEG
     
  3. Fox11 thread starter macrumors member

    Joined:
    Nov 8, 2009
    #4
    As long as "unstable" doesn't mean dangerous (it doesn't, does it?) then that sounds great!
     
  4. TEG macrumors 604

    TEG

    Joined:
    Jan 21, 2002
    Location:
    Langley, Washington
    #5
    By unstable, I mean that it may fall out, and it doesn't lock in like the Apple cables.

    TEG
     
  5. heySparky macrumors regular

    heySparky

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    Location:
    Oregon
  6. lbodnar macrumors regular

    Joined:
    Jan 5, 2004
    Location:
    UK
    #7
    Amazingly, this is not that simple.

    I don't know if you guys have mains socket grounding as standard in the US but here in the UK all residential sockets are three-pronged and have grounding as a legal requirement.

    When you use Apple's plug or power cable the laptop's case will be grounded via shiny metal "button" on the power supply. If you use two-wire cable then the laptop case is "floating" related to ground. This can cause quite a large residual voltage on the laptop case. Power supply bricks usually have a pair of capacitors between two power wires and [now floating] case as a part of EMI filter and you can end up with up to 1/2 mains voltage applied to case as a result. It is still safe though as the current will not be large enough for any serious shock.
    But if you ever noticed tingling sensation while gently touching the metal part of the laptop then this is it. Especially if you stand on a floor.

    It is not really a big issue but may present a problem when you hot-plug something that has independent (and proper) grounding like external HDD with its own power supply or external monitor, etc. If you are unlucky, large voltage differential between the two can burn out the interface circuits. Most connectors are designed so that GNDs or shields makes the contact first but still there is a chance of a failure.

    If you just use the laptop on its own then it is hardly an issue at all.
     
  7. TEG macrumors 604

    TEG

    Joined:
    Jan 21, 2002
    Location:
    Langley, Washington
    #8
    In the US, grounding is optional. All Apple Power Supplies can be operated ungrounded (because the figure-8 connectors fit the "B" shaped grounded connectors), and at least at 120V, work just fine. While I have no experience in 240V countries, I use both grounded and ungrounded power adapters with my PowerBook G4s, and have use grounded power adapters with non-grounded cables, and the duck-end adapters, with zero problems. I do know that the Apple supplied adapters for the UK, that you can buy from Apple in the US, have a plastic pin on the grounding pin, as they are to be used mostly with the iPod/iPhone USB Adapters, but work with Regular Power Adapters and Airport Expresses.

    TEG
     
  8. lbodnar macrumors regular

    Joined:
    Jan 5, 2004
    Location:
    UK
    #9
    Here is an illustration to my message above.

    1st picture shows the details of how laptop case is grounded when using proper parts.

    2nd picture shows the presence of ~36V AC on the MacBook case when using 2-wire power cord. When Apple 3-wire cord is used the voltage reading is zero.

    Our mains voltage is 240V AC. The reference point was Cinema HD display that is properly grounded via 3-wire power cord.

    TEG, you are right, the UK quickie plastic plug that allows wall mounting of the power block does not have ground link but the power cable does! :eek:
     

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  9. mousouchop macrumors 6502a

    mousouchop

    Joined:
    Oct 22, 2008
    Location:
    New York
    #10
    I have used random cords like that in a pinch. I work at an IT help desk, and when I only bring the MBP brick and forget the extension cord, I just steal on of the cables from a camcorder chargers (like the one you linked). Have never had an issue.

    Alternatively, you could buy one of the white extensions from eBay. I bought one of these for use with my Airport Express. [Like this one]
     

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