A hinge assembly includes a main member having a main cam member and a bore extending generally along an axis of rotation. In an example diaphragm pump, a discharge valve can be opened by the pressure of fluid leaving the pump and can also be opened by an intermittent mechanical linkage actuated by the reciprocating member powering the pump. An independent position sensor indicates the mechanical lateral position of the servo sensor at the sensed servo edges. These openings are selectively alignable with a pair of openings disposed on a vertical bar to pivotally attach the vertical and horizontal bars to one another. Both plates of the internal parasitic capacitor are discharged at turn off, cutting the parasitic discharge time in half.