My SmoothieBoard has a problem

I am building my 3D printer. I have tested movement and heat in the bed and hotend but I have not melted plastic yet.

My SmoothieBoard has been working and yesterday I ran the tuning procedure to tune the PID parameters for the Bed and Hot End.
Today my smoothieBoard will not boot. I get only one led (VBB) on solid and a solid lit screen on my LCD panel.

I have a 5 V regulator mounted on the SmoothieBoard and a second regulator mounted on the LCD adapter card.

Measuring the voltage showed the 5V line on the SmoothieBoard at 0 .6 volts. The voltage on the LCD adapter board is 0.6 v on the smoothie side of the 5v diode and 5v on the adapter side.

My first guess was a regulator failure. I connected a 5 V external power supply to the smoothieBoard without removing the 5v regulator. The voltage on power supply with no load was 5.5 v yet the 5 v line on the SmoothieBoard is still 0.6 V.

What should I try next? Is the next step to unsolder the regulator?

I noticed that a smoothieBoard led flashes when I rotate a stepper motor with power off. Could I have zapped the board when I moved the z platform for leveling today?

Imported from wikidot

This could be a short, or EMI/electrostatic shock/motor rotation destroying the board. Very difficult to know.

Please start by disconnecting everything, removing the regulator, and inspecting the board very closely.

My problem was a washer on the z endstop shorting the endstop power.

Hey. What 3D printer do you have ?

I am building an Eclips3d corexy printer.

Thank you for the help. When you are ready for more beta testers for the Version 2 board I am interested in helping. (I am an experienced system programmer.)