Abstract: An improved mechanical arrangement is disclosed for removably attaching a circuit board to a mounting box. An edge portion of the circuit board containing the board's heat conductive strip slides between two elongated heat sink guides attached to the mounting box, the edge portion containing a vertical cam shaft with an eccentric cam exerts pressure upon one of the heat sink guides in response to a rotation of the cam shaft by an attached lever-type handle. Since the cam shaft is attached by support members to the circuit board, the shaft acts as a beam spring so as to force the heat conductive strip against the second of the heat sink guides.