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Can a Magsafe i/o Board charge a battery externally?

I'm trying to narrow down the power problem that I'm having with my Macbook Pro. I received a dead Early 2008 15" Macbook Pro for free and I'm trying to bring it back to life. When I connect my Magsafe charger, I don't get any light on the charger. I have two Magsafe chargers available to me (both 85 watts, one "T" shaped and one "L" shaped). Neither charger works with this MBP. Both chargers work perfectly with my 2010 MBP.

The symptoms seem to indicate a bad Magsafe i/o board in the computer. So I ordered a new one (made sure it was the correct one) and I installed it yesterday. Nothing has changed. I still get no light on my Magsafe charger and the computer still won't turn on.

So I guess I'm looking for some information on how to trace this power issue. If the Magsafe board is good, shouldn't it still charge the battery even if the Logic Board is bad? The internal battery cable goes right from the Magsafe i/o board to the battery and doesn't involve the logic board. Logically it looks like the battery should at least charge even if the Logic Board is bad.

So I'm wondering if I'm missing something or if maybe I did something incorrectly. So I'm looking for any information that someone can provide about how power gets routed to the system so that I can try to narrow down where it's going wrong. Any thoughts on this issue would be appreciated.

Answered! View the answer I have this problem too

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There's a SMC controller chip on the logic board that manage the magsafe powering and charging functions. If this controller is faulty (or something wrong in the power circuit) there will be no power coming in the computer from the ac adapter and no green or yellow light on the magsafe tip.

ABCellars could give a better explanation than mine on the subject.


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The magsafe will not put out the 16.5v - 18.5volts it supplies until the SMC and the magsafe are "shaking hands" and the SMC tells the Magsafe it can. Your lack of the LED(s) lighting on the magsafe indicate that the SMC and power adapter don't know the other exists. To answer the question in your title, not touching the rest yet, is not with the intended power supply.

If you have replaced your left I/O board with a good one. Then either that board isn't talking with the logic board or the motherboard has problems. With the information given, I would start by checking the magsafe connector for residue or debris. The center contact (the small one) on the magsafe is where it communicates with the SMC. After that I would double check the connections of the power cable that connects between the I/O board the logic board. If those are good I would inspect the cable ends and the socket on the logic board for any bent or burnt pins with a jewelers loupe. I would also inspect the area around that socket and the area on the other side of the board directly underneath it for any signs of burning such as discoloration or charring - Inspect both the board and components in those areas. This is a 12 layer board with most of the power running through sub levels.

Please give us the last 3 characters of your serial number so we can determine your exact machine and better be able to assist you. Please give us any history of the machine passed on to you. Has this ever experienced liquid damage?

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I don't know anything about the history of the machine. I received it as-is. I have inspected all of the components and was unable to find any signs of liquid damage or burning. I've tried 2 different Power Cables, so I'm pretty sure that they are ok as well. So I think that maybe I just have a bad SMC on my board. Thank you for your answer!


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I have a similar problem with my macbookpro and the damaged mainly caused because of the water which reached the tip of the charger and I inserted it in to the PC but even the pc refused to start working. I tried many other chargers. Any help appreiciated. Worku, May 2014

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Josh will be eternally grateful.
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