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发布于 2012 年 6 月, 型号 A1278. Intel 处理器，支持 Turbo Boost, 最多 512 MB DDR5 显存

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MacBook Pro 13" (A1278) won't turn on unless batt disconnected

I am CompTIA A+ Certified since 2016 and I have made many repairs on PC laptops and desktops, such as LCD screen and motherboard replacements, etc.

This is my first Macbook. It won't power on when you push the power button with the MagSafe connected or disconnected. My customer did not report any spills.

At first I thought maybe it was a bad battery or MagSafe AC Adapter. With the MagSafe connected I have a bright solid Green LED located at the L head, which would indicate a full charge on the battery. I removed back cover, disconnected the battery from the logic board, then reconnect the battery and when I connect the MagSafe to the system, nothing happens and I get no response from pushing the power button.

If I perform the SMC reset with the MagSafe still connected, by holding the Shift+Control+Option keys and the Power button at the same time then releasing all keys and the power button at the same time I see no change in the color of the little light on the MagSafe adapter. The light remains bright Green.

If I push the button on left side of case, I get all 8 LED's. If I remove the MagSafe from the Macbook and disconnect the battery from the logic board then hold the Power button for 10 seconds then reconnect the battery to the logic board the Macbook powers on immediately and boots to the logon screen, I enter the password and it boots to the desktop as it should.

I can disconnect the MagSafe from the system and it will remain powered on with the battery. Over time I can watch the battery charge percentage decrease or count down as it uses the battery. I can then reconnect the MagSafe and the light on the L head turns to Amber indicating a charging condition until the battery reaches 100% and the little light on the L head changes to bright green. I think I can rule out the battery and the MagSafe AC Adapter as being faulty.

It appears the battery is healthy and the MagSafe is operating as it should. Once the Macbook boots up it seems to operate fine so I think maybe the logic board does not have an issue. All the the other keys on the keyboard seem to function correctly. I am leaning towards replacing the keyboard which would also include the power button. What do you all think?

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You do have a logic board issue with the charging logic. There are four MOSFET’s two which switch the power feed between the MagSafe to either the battery or the logic board. Then you have a different set of MOSFET’s which switches the power from the battery to the logic board.

In your case this second set of MOSFET’s are not responding properly. Inspect the logic board for burnt components as well as cold solder joints!

Locate the needed schematics and boardview for your system so you can trace out the logic and identify the MOSFET that has failed and/or the cap/resistors around it that may have been damaged.

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Thank you Dan for your response and sharing your knowledge. I really do appreciate it! Soldering and desoldering resistors and capacitors on logic boards is outside my skill set. I went back to school to retrain after working in manufacturing for 30 years when the company went out of business. I got my BS in IT and then didn't find work in my field of study so I went back to work in manufacturing and now I'm retired and do computer repairs out of my home. I'll have to see if the owner wants to replace the logic board or not. I was checking on eBay and Amazon for the board, but that scares me a little because I read a horror story about someone buying one that the seller apparently got from a pawn shop and the buyer couldn't reinstall the OS because it was still tied to the previous owners Apple ID. Bad news!

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You won't encounter a users Apple ID tied to the logic board with this series of MacBook Pro. You might encounter a firmware locked board though.

I don't use Amazon or eBay for logic boards as its too iffy on getting a bad one and then fighting to get my money back. Instead I go to a proper parts house.

Where are you located so I can aim you to a local one to you (as best as I can)

由完成的

I live in East Alton, Illinois which is like 30 miles north of St. Louis, Missouri. Are you suggesting I could take the logic board to a shop that would repair it?

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That would likely be the cheapest way. Otherwise I would look at either the iFixit store MacBook Pro 13" Unibody (Mid 2012) 2.5 GHz Logic Board or BeetTech - MacBook-Pro 13" Unibody Mid 2012 2.5 or 2.9 GHz Logic Board for a replacement board.

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I would consider taking the board to a repair shop if I could find one that isn't too far away from my location. Otherwise, I would probably purchase the board from the iFixit store.

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