Ender 3 Won’t Start - flashing screen and blue LED on main board Just received my second Ender 3 (see my other questions for the problems that first one developed). Figured it best to have a spare while I upgrade my first one with an ABL. 

I assembled it as normal, without any issues, but on applying power the LCD screen just flashes on and off continuously along with the blue LED on the main board. See photo. 

When I power it off, the Ender 3 logo appears briefly before it goes black. I am in the U.K. and running 240v setting. Is this likely the power supply or the motherboard? I already tried another screen and same problem.
Just after I posted this I tried swapping various components with my other Ender 3. 

It turns out a faulty power supply will produce this effect. When I swapped out the power supply it started normally.