Laser Tube is hissing when not firing, after installation of Cohesion3d board

as soon as I turn on power to the laserboard, even if the powerswitch on the k40 is off, the laser tube starts a gentle hiss, like power is already going to it. but not enough to do anything, this cannot be good.

It’s not the laser tube hissing, it’s the stepper motors. Hold your ear to one of them to verify :slight_smile: It’s perfectly normal and an artifact of the style of stepper driver that the board uses.