If you can see a motor spinning when the platter is off, then it's probably driven by an idler wheel. Direct drive turntables use the platter as the armature, which is part of the motor. Without the platter installed, the motor is incomplete and there is nothing to see spinning.If direct drive, the platter should spin freely with no power applied. If driven by an idler wheel, it probably shouldn't unless the speed selector is positioned between 33 and 45, where the wheel is transitioning between drive surfaces.