So after 3 month of my 3d printer working - one day it stops to communicate with PC. After some research - the dead 5V regulator is found at Arduino board. I run it at 14V because of heatbed. The voltage at the heatbed is 12V only when I put 14V from the power supply. 2V drops on wires to the heatbed. So I must put 14V from the power supply. I replaced regulator with LP2950L 5.0. It is getting hot, but works for 2 week now.