MacBook pro boot problem Mid 2012 - Yosemite

Question

Dear, it is a fairly common problem, I've googled and reviewed in detail the forum and can not find a similar case.
It turns out my mac began to put slow and not pay much attention to it (assumed it was subject software), until one day watching a series screen froze, pressed the button to turn it on and saw him again appeared folder with flashing question mark.
What did I do:
1. Try to restore and repair it online, but did not recognize the hard disk.
2. Resetie PRAM, SMC and stuff, 'but nothing changed.
3. opened and proceeded to clean the feet and check for any visible damage. But there was nothing, but when I did this in addition to flashing the folder, began to alternate with forbidden sign (circle with a line through it) and apple mac, bone sandwiched mind flashed 3 things.
4. opened again and disconnect the DVD and remove Kingston RAM, and it worked again.
But after three days it off and began the same drama, so here I opened it, I put the ram and plug it again and sopresivamente worked.
Until yesterday, it froze and I had to restart and bam, I returned to the same wea. Hahahaha.
Then I am not able to diagnose it, and I'd like to help you answer something.
He understood that when a hard drive dies, dies and nothing works again, this however is still alive, when he wants, but still alive.
I read that it could be the motherboard that is dying, but not know how to check.
I also read that it could be some port or connector HDD.
I am traveling in a village in the middle of nowhere, never mind an Apple store or authorized service lol.
Thanks in advance and hope to save my mac.

Answer 1

trying to format a USB flash drive and see how stable would. Otherwise an authorized service agency for diagnosis

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Answer 2

Personally what I would do would be to start to rule, first try with other memories, if you follow the problem, changing the hard drive. But I think in your case would be complicated by the fact that you're in a village in the middle of nowhere.

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Answer 3

When the power fails the hard drive smart informs, review it with HDTUNE, however if the smart says nothing means that no cable problem. RAM test did separately on another computer? Sometimes the test does not fail on the same computer.
You always have the option to download the diagnostics Apple hardware before DVD came in recovery, today you googling for download version of your computer and make it bootable from a USB flash drive, that thing checked all the equipment.
What seems more fault indica SMC when mad. But you can make a very simple test, if you have an external drive, install OSX or Windows in the external disk and use the computer for a couple of days from the external drive if no fault indicates that your thesis inner disk gives problems.

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