Released June 2012, Model A1278. Intel processor with Turbo Boost, Up to 512 MB DDR5 Video RAM

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Its my logic board working?

Is there any method or lights to check if the logic board of my MacBook Pro A1278 Mid 2012 is working?

I have installed two logic boards in my system and the computer is still not turning on? Neither fan movement, nor adapter green light!

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Other than the MageSafe connector LED there is no other diagnostics to prove the system is able to get power.

Are you sure the MageSafe power adapter is good? Is the battery charged (using a second system if you can)?

Sometimes it's a matter of tracing out the power feeds to see whats happening. Using a multimeter you should be able to trace out the power from your MagSafe connection to your logic board. Are you able to do that?

Often times I need to replace the MagSafe DC-In board unit as the contacts are worn or damaged. Here's the IFIXIT guide: MacBook Pro 13" Unibody Mid 2012 MagSafe DC-In Board Replacement

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Thanks Dan for your reply!! I have two chargers, the original magsafe and other non original charger!! None of them works. The led on the power plug does not turn on with any of the two charges.

I read in other publication, that it is possible to you can test the LOGIC BOARD, before installing the motherboard back into the case and connecting anything and plugging in the AC adapter into the MagSafe board.

The LED on the power plug has to turn on and remain solid green. If the LED lights up, then the Logic Board is working. If the LED doesn’t turn on, try reconnecting the MagSave board to the motherboard and test again.

If still there is no LED light, it’s possible the MagSafe board was damaged and has to be replaced.

I have ordered another MagSafe board to see if this is the problem. I Would appreciate any other suggestion from your side.

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I'm not sure if testing your board externally will help you here. Yes, people who to logic board repairs have test rigs setup so they can test the board while working on them. Basically duplicating the pieces that make up your system.

The MageSafe LED (Green or Orange) only tells you if the system's power circuit is working and SMC services sees the MagSafe charger. There is a symbiosis relationship between the charger, battery & charging logic on the logic board.

Without knowing what happened with your system you could also need other parts. Clearly you have a power services issue here, but it could be something more. Give us more background on what happened.

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Did you spill something on it and short out the keyboard? If so you need to replace it. This is for the 2010 but will show you how: MacBook Pro 13" Unibody Mid 2010 Keyboard Replacement

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Unless there is something wrong with the circuits inside both of the logic boards you installed (PP3V42_G3H_REG, SYS_ONEWIRE and SMC circuits) , there is very likely something wrong with the AC adapter! The 820-3115-B board for the 2012 MacBook Pro should boot up automatically regardless of the keyboard if properly functioning.

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