My laptop turns off randomly

I have lenovo thinkpad edge,it turns off randomly, I tried a plenty of solutions but useless, it's not overheating I cleaned a fan but still keeps turning off when I connect to wifi or opening a software or watching video..
What can I do? Any help!
 
Remove the battery and run only on the AC adapter. See if doing this solves the shutting off. If it does, replace the battery
 
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