25EH5 Tubes

25EH5 is a cold-cathode tube made by the Raytheon Company in the mid-20th century. It is a triode tube and was primarily used in television receivers as the video output stage. It is a thermionic valve that uses indirect modulation. The tube uses a hydrogen-filled envelope and the electrodes are connected to a single plate. The plate voltage is maintained at a DC level and the cathode voltage is variable. The tube has a maximum plate voltage of 250 volts and a maximum plate dissipation of 2.3 Watts. The tube can operate at up to 40 mA of plate current. The transconductance of this tube is approximately 2 mA/V. The internal construction of the 25EH5 consists of four sections - an ignited heater section, an anode section, a control grid section and a shield grid section. The grid section is wrapped in shielding material to reduce signal interference. It is a low-noise device and is relatively robust. It is suitable for use in a wide range of television receivers.