An adaptive closed-loop controller is described that reduces repetitive speed variations of precision rotatable mechanical components, such as rollers, casting wheels, pulleys, gears, pull rollers, extruders, gear pumps, and the like. The support piece has at least first and second bearing surfaces defining a fixed position for the display means in the support piece in relation to the aperture in the dial, the fixed position being defined in a parallel plane to the dial. The decoupling circuit includes a first inductive element, a first resistor, and a first capacitor coupled together in series between the first current electrode of the power transistor and the voltage reference. A fusible tip is disposed at a distal end of the delivery tube that seals the delivery tube.