disclosed is an arrangement for connecting a plurality of transistors to a heat sink surrounding one end of a control motor for a mailing machine . the motor is a conventional bi - directional stepping motor which controls various operational functions of the mailing machine . the direction , speed and continuity of the rotation of the motor rotor are controlled by a plurality of transistors which receive appropriate signals from a microprocessor . the transistors generate a substantial amount of heat during operation of the motor and are mounted on a heat sink connected to the motor in order to dissipate this heat . in the arrangement disclosed , there are two sets of three transistors each , and each set is mounted on the heat sink by a single screw , washer , insulator and hold - down spring , rather than by separate screws , lock washers , flat washers , insulators and nuts for each of the six transistors , thereby greatly reducing the number of parts required to assemble the transistors to the motor and the labor time required to do so .