It requires use of a fan or blower, a sealed chassis plenum, openings around the socket, and a chimney which fits around the anode and directs the moving air through the anode fins. This tube also fits any standard loktal tube socket, or specialized sockets for the 4CX250B, such as the Eimac SK640. The low-cost loktal sockets seen in antique radios, made of phenolic plate material, are not recommended as they will not tolerate the higher operating temperatures of the 3CX300A1. Figure 1 shows a suitable mounting scheme for the SK2A on a chassis. There should be openings around the socket body, to pass cooling air.
Air can then pass the socket and flow upwards to the anode fins.
Best airflow is obtained when the opening around the socket is roughly equal to the open area of the anode fins, to minimize back pressure. This area is about 754 square millimeters, or about 1.1 square inches. Since a chimney is required around the tube, the socket is shown mounted below the chassis in Figure 1. The chimney will then slip over the tube and rest on the chassis, thus directing the air past the lower body of the tube and through the anode fins. The standard Eimac SK606 chimney is suitable.