I received an in person customer recently whom brought me a Macbook Professional circa 2011. This laptop computer had the Mac shuts down randomly problem. Whenever, I receive a computer that randomly shuts down, I normally strip it down as much as possible.
What I mean by this is that I remove all external devices. For example USB flash drives, USB dongles, keyboard, mice, etc. I will also release any possible electric static discharge.
Power off that computer. Disconnect power cable from both wall outlet and computer. Press the power button for at least 30 seconds.
On laptop computers I remove the battery and set it aside. Then I take off the cover. This Macintosh requires multiple covers that you have to take off.
Also, you will need to remove 4 screws on each side. Two screws are removed from the rear. You will need to remove 4 screws on the bottom.
Also, you will have to remove the battery. A smaller cover protects the random access memory. This Macbook Professional circa 2011 had a failing DVD optical drive.
There are four screws to remove to take out the DVD optical drive. However, I could not loosen these screws so I decided to leave the DVD optical drive installed. I would rather not strip screws and create even further problems.
I disconnected the hard drive serial ATA cable. You must take the hard drive out in order to disconnect this cable. There are four screws that must be removed in order to lift out this hard drive.
Finally, I tested the two dynamic inline memory modules installed. They were both DDR2 5300 random access memory modules. I cleaned them with a dry eraser.
I tested each individual random access memory module in each slot. There were two memory slots present. One of these memory modules would sometimes cause this Macbook Professional to NOT boot.
The other memory module did NOT cause this problem. With the process of elimination, I deduced that it was a faulty dynamic inline memory module. I installed a two gigabyte DDR2 6400.
The original memory modules were both 1 gigabytes in size each. I have left this Macbook Professional circa 2011 model powered on for over two days now and it has NOT powered off once. Another interesting change I noticed was that now the battery charges.
This customer had told me that this battery no longer held a charge. When it comes to troubleshooting Mac shuts down randomly problems, there is a large list of possible culprits. Power supply, motherboard, memory, operating system, etc.
I normally start off with hardware troubleshooting, because often times this is the culprit. A faulty or failing memory module is NOT uncommon. Also, even a faulty or failing memory slot can occur.