SOLVED: Screen + 3 beeps problem! - MacBook Pro 13" Unibody Mid 2012 - iFixit
The three beeps has historically been a RAM issue. However, recently I have seen three 2011-2012 machines where it is not and is the logic board. To test use just one stick of RAM and remove the other. Try it in one slot and then the other slot. On each try take a look at the system configuration... - MacBook Pro 13" Unibody Mid 2012
Laptop IBM lenovo thinkpad x240 core i5 , Laptop cũ, Laptop xách tay
Does this Thinkpad really have only one RAM slot? Or is there another one on the back of the board (i.e. under the keyboard).