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Mid 2012 model, A1278 / 2.5 GHz i5 or 2.9 GHz i7 processor.

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Why is my MacBook powering up then shutting off immediately

So a spillage occurred over my macbook pro a few days ago over the keyboard, which lead to everything else fully functioning but the keyboard was not to certain extent, so I decided to replace the keyboard myself.

I brought the keyboard off ebay and the needed tools and followed the relevant guides as to how to replace it, didnt see any liquid damage on the logic board and once I got to the where the keyboard is located I cleaned up the residue with isopropyl alcohol.

I put the new keyboard in and put it back together again and tested it with the bottom open, pressed the power button and the LED comes on, the fan spins and the hard drive spins up then within 2 seconds it shuts off, if I continue holdig the powet button it will cycle.

Is the logic board dead? Or is it something else?

Sorry for the long paragraphs

Any help would be appreciated

Thanks

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There are many variables in this case. If you want causes, here are a few:

It should be a bad key board and you need to try a new one. Usually the laptop just doesn't start off of a bad keyboard, however you can try to rule it out. If it was starting off of your old keyboard, overlay it and connect it instead of the old one and start the laptop. If it works normally (but with missing keys), you'll know it was the keyboard and get a new one.

It could be a problem on the main board, either pry damage during the repair, or something was getting corroded and died on you during the repair.

It can be fixed but more on that later, as you'll need a multimeter, the board number, the schematics, the board view, and possibly a soldering iron and hot air station and the ability to micro-solder.

Using the above you can track the problem and solve it.

For now, look for sources of heat (not warmth). Touch around the board when it is starting or trying to. Anything stands out as too hot?

If not try starting from your battery alone, or charger alone, or with both charger and battery connected. Any difference?

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When I plug in the magsafe power cord, the thing repeats it self, it turns on and off repeatedly within seconds without me pressing the power button. When I Unplug the cord then the cycle stops.

And ill try it with the old keyboard and look for heat sources.

by

Umm could be the keyboard. When you connect a charger and the board does not "see" a keyboard connected, it immediately starts. Try the old one indeed.

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So I have made a few new discoveries and it seems the problems have become much more varied than before. I decided to thoroughly clean the motherboard with alcohol and retry after it dried and also replaced the thermal compound. I discovered that when I disconnect the track pad ribbon cable, it would boot up but when I plug it in the computer refuses to start with the same problem I started out with, the keyboard works fine as tested it in single user mode, now what do I do about this trackpad problem?

Also, now that i replaced the thermal compound, the fans seem to be spinning much faster and the fan is much louder than before I replaced it. What could have caused this?

However, once I boot into the OS it spontaneously restarts saying there was a problem which seems to be a kernel panic, would that be due to the disconnected trackpad, bear in mind the hard drive is really old and failing.

So many problems, any help would be very much appreciated

by

@minhazul, you're all over the place. When you want to isolate a problem, you have to change or eliminate one thing at time. And try to remove as many variables as possible. Here you are adding them.

First your trackpad could be bad/shorted. Which is why laptop is not starting off of it. One way to make sure is try a second trackpad, or perform an SMC reset.

Second, when you replaced the compound, you either did not do it properly, used the wrong product which is not evacuating heat, or damaged something during the process. All of these will cause the fans to spin too quickly. Unless the SMC reset brings them back to normal.

If you find that a reset did nothing, you will need to unplug your HDD, try a new trackpad, and see if laptop starts to a flashing folder. If it does, you had a bad trackpad.

As for the heat compound, what did you use? What method did you follow?

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Sorry about being all over the place.

The only reason I replaced the thermal compound was because I decided to thoroughly clean the entire motherboard as it was really dirty and had lots of dust on and the mac book was years old. I cleaned it throughout and even the old thermal compound off. I was going to use arctic silver 5 but I couldnt find it so I used the thermal compound that came with the CoolerMaster Hyper 212 EVO CPU fan, and I placed a little dot in the middle of the chip and put the CPU fan back into its place and reassembled everything.

As for the trackpad, Ill try another trackpad from another macbook and see how that goes but it does boot, just very slow and decides to spontaneously restart.

Thanks

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