{"type_number":"849","canonical_url":"https://tubeofile.com/tubes/849","manufacturer":"RCA","tube_type_key":"power_triode","tube_type_display_name":"Power Triode","base_name":"Jumbo3","description":"Large directly heated transmitting triode with thoriated tungsten filament. Designed by RCA/GE for high-power RF and audio-frequency amplifier, oscillator, and modulator service. Capable of 300W plate dissipation. Jumbo 3-pin base with plate connection via top cap. Glass bulb (T-20).","is_directly_heated":true,"completeness":"high","notes":["DHT tube: the thoriated tungsten filament serves as the cathode; there is no heater-cathode isolation.","Maximum plate current is 350 mA.","The plate (anode) connection is made via a top cap; the base carries only filament and grid connections.","Class A amplifier at Va=3000V: Vg=-132V, Ia=100mA, mu=19, gm=5.8 mA/V, ra=3250 Ohm, rl=18000 Ohm, Po=100W.","Designed primarily for broadcast transmitter service; also used in high-power SE audio amplifiers.","Pa_max is 300W (CCS). The tube requires forced-air cooling in most installations at full ratings.","Filament may be operated on AC or DC. Grid bias voltage is referenced to filament midpoint."],"references":["https://tdsl.duncanamps.com/show.php?des=849","https://www.radiomuseum.org/tubes/tube_849.html"],"source_urls":{"r_type":null,"tdsl":"https://tdsl.duncanamps.com/show.php?des=849","radiomuseum":"https://www.radiomuseum.org/tubes/tube_849.html"},"raw_equivalents":["CV2669"],"equivalents":[],"similar":[{"type_number":"211","reason":"Smaller transmitting triode (75W Pa_max vs 300W); same general application class but much lower power capability","has_detail_page":true},{"type_number":"845","reason":"Smaller transmitting triode (100W Pa_max vs 300W); same UX4 pinout family but different base and much lower power rating","has_detail_page":true}],"pins":[{"pin_number":"1","function":"Filament","function_code":"h","notes":null},{"pin_number":"2","function":"Grid","function_code":"g1","notes":null},{"pin_number":"3","function":"Filament","function_code":"h","notes":null},{"pin_number":"TC","function":"Plate (Top Cap)","function_code":"a","notes":null}],"specs":[{"key":"Vh","display_name":"Heater Voltage","value":"11","numeric_value":"11","unit":"V","param_group":"heater"},{"key":"Ah","display_name":"Heater Current","value":"5","numeric_value":"5","unit":"A","param_group":"heater"}],"sections":[{"section_number":1,"section_label":"Triode","tube_type_key":"power_triode","specs":[{"key":"Va_max","display_name":"Anode Voltage (max)","value":"3000","numeric_value":"3000","unit":"V","param_group":"absolute_max"},{"key":"Pa_max","display_name":"Anode Dissipation (max)","value":"300","numeric_value":"300","unit":"W","param_group":"absolute_max"},{"key":"Ik_max","display_name":"Cathode Current (max)","value":"350","numeric_value":"350","unit":"mA","param_group":"absolute_max"},{"key":"Va","display_name":"Anode Voltage (typical)","value":"3000","numeric_value":"3000","unit":"V","param_group":"typical_operating"},{"key":"Vg","display_name":"Grid 1 Bias Voltage","value":"-132","numeric_value":"-132","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"100","numeric_value":"100","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"3250","numeric_value":"3250","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"5.8","numeric_value":"5.8","unit":"mA/V","param_group":"typical_operating"},{"key":"mu","display_name":"Amplification Factor (μ)","value":"19","numeric_value":"19","unit":"—","param_group":"typical_operating"},{"key":"Pout","display_name":"Output Power","value":"100","numeric_value":"100","unit":"W","param_group":"output"},{"key":"rl","display_name":"Load Impedance","value":"18000","numeric_value":"18000","unit":"Ω","param_group":"output"}]}],"synced_at":"2026-04-07T12:34:08.383Z"}