An assembly includes a ring frame having first and second open sides and an electrical connector block; a mounting structure to which the ring frame is secured; a plurality of power and signal cable connection points defined on the ring frame; and a plurality of power and signal cables coupled to the power and signal cable connection points and the connector block. First and second covers are secured to the ring frame. Each of the first and second covers is open on one side facing the ring frame and defines a mounting cavity. A plurality of heat-dissipating electronic components are mechanically and thermally coupled to the first and second covers and located in the mounting cavities. The heat-dissipating electronic components are releasably electrically coupled to the electrical connector block.