X Y stepper disabled after movement Rostock delta
I have DIY Rostock delta equiped with Sanguinololu 1.3b. Firmware Repetier 0.92.9. Everithing worling fine except X and Y steppers are disabled after movement. So if head is moved down for some value, all stepper stops, Z carriage hold place but X and Y carriage drops. Trying movement by hand and Z carriage hold stil and X and Y carriage can be moved with no resistance.
Tried till now : replacing steppers Z always enabled X and Y disabled, replacing Pololus z always enabled XY disabled. Check with osciloscope shows enable signal on Z axis is logic LOW and X and Y are logic HIGH.
In Repetier-Firmware configuration tool unchecked Disable when unused for X, Yand Z stepper. In Repetier host unchecked Disable Motors after Job/Kill.
All suggestions are are welcomed
Thanks in advance