Triode RD30XM

Air-cooled triode for frequencies up to 60 MHz. Heating 10 V / 240 A, 15 kV max. anode voltage, 30 kW anode power. These tubes were used not only in transmitters, but also in industrial generators for radio frequency heating, such as machines for welding of plastics. The transmitter tubes occasionally developed a temporary internal short circuit. The tube could be used even after the short, but the transmitter had to be equipped with circuits that protected the tube from destruction by the large short circuit current. If the transmitter detected a short, the power supply would be disconnected and the high voltage filters were discharged. This had to be done in few microseconds, ohterwise the tube would be damaged. The protection circuit was tested by shorting the anode of the tube, which was supplied with several kilovolts, to the ground with a thin wire. A properly working protection circuit would ensure that the wire would not burn. The triggering of the protection circuit was accompanied by a loud bang, similar to a hand grenade explosion, which was produced by the spark gap switches that shorted the high voltage circuits.