{"type_number":"350B","canonical_url":"https://tubeofile.com/tubes/350B","manufacturer":"Western Electric","tube_type_key":"beam_tetrode","tube_type_display_name":"Beam Tetrode","base_name":"Octal","description":"Beam power tetrode of the heater-cathode type, designed for use as an audio-frequency amplifier or radio-frequency oscillator. Developed by Bell Telephone Laboratories for Western Electric.","is_directly_heated":false,"completeness":"high","notes":["The 350A, 350B, and 367A have essentially identical static characteristics but differ in lead-out arrangement and basing.","Heater current is 1.6A — nearly double that of the 6L6 (0.9A). While the pinout is identical to the 6L6 family, the 350B is not a drop-in replacement in circuits designed for 6L6 heater current without verifying the heater supply can handle the additional load.","Maximum grid circuit resistance differs by bias type: 0.1 MΩ for fixed bias, 0.5 MΩ for cathode bias.","Developed by Bell Telephone Laboratories and manufactured by Western Electric for AT&T telephone system applications. The USN-CW-350B is the US Navy designation for this tube."],"references":["https://static1.squarespace.com/static/5f0983034219c6086e8100ac/t/5f4558b5b225082cb861b3ec/1598380215739/350B.pdf","http://www.tubezone.net/pdf/we350b.pdf"],"source_urls":{"r_type":null,"tdsl":"https://tdsl.duncanamps.com/show.php?des=350B","radiomuseum":"https://www.radiomuseum.org/tubes/tube_350b.html"},"raw_equivalents":["CV1799","350A"],"equivalents":[{"type_number":"350A","equivalence_type":"direct","notes":null}],"similar":[{"type_number":"25BK5","reason":"Similar beam tetrode but Noval base with 25V heater vs Octal/6.3V for 350B","has_detail_page":true},{"type_number":"367A","reason":"Same internal structure and electricals as 350B but different base configuration and shorter/rounder glass envelope","has_detail_page":true},{"type_number":"6L6","reason":"Same octal pinout and similar beam tetrode characteristics, but 350B draws 1.6A heater current vs 0.9A for 6L6 — heater transformer must be rated accordingly","has_detail_page":true}],"pins":[{"pin_number":"1","function":"No Connection","function_code":"nc","notes":null},{"pin_number":"2","function":"Heater","function_code":"h","notes":null},{"pin_number":"3","function":"Anode (Plate)","function_code":"a","notes":null},{"pin_number":"4","function":"Screen Grid","function_code":"g2","notes":null},{"pin_number":"5","function":"Control Grid","function_code":"g1","notes":null},{"pin_number":"6","function":"No Connection","function_code":"nc","notes":null},{"pin_number":"7","function":"Heater","function_code":"h","notes":null},{"pin_number":"8","function":"Cathode & Beam Forming Plates","function_code":"k","notes":null}],"specs":[{"key":"Vh","display_name":"Heater Voltage","value":"6.3","numeric_value":"6.3","unit":"V","param_group":"heater"},{"key":"Ah","display_name":"Heater Current","value":"1.6","numeric_value":"1.6","unit":"A","param_group":"heater"}],"sections":[{"section_number":1,"section_label":"Beam Tetrode","tube_type_key":"beam_tetrode","specs":[{"key":"Va_max","display_name":"Anode Voltage (max)","value":"360","numeric_value":"360","unit":"V","param_group":"absolute_max"},{"key":"Vs_max","display_name":"Screen Voltage (max)","value":"270","numeric_value":"270","unit":"V","param_group":"absolute_max"},{"key":"Pa_max","display_name":"Anode Dissipation (max)","value":"27","numeric_value":"27","unit":"W","param_group":"absolute_max"},{"key":"Ps_max","display_name":"Screen Dissipation (max)","value":"4","numeric_value":"4","unit":"W","param_group":"absolute_max"},{"key":"Ik_max","display_name":"Cathode Current (max)","value":"125","numeric_value":"125","unit":"mA","param_group":"absolute_max"},{"key":"Rg_max","display_name":"Max Grid Resistor","value":"0.1","numeric_value":"0.1","unit":"MΩ","param_group":"absolute_max"},{"key":"Va","display_name":"Anode Voltage (typical)","value":"250","numeric_value":"250","unit":"V","param_group":"typical_operating"},{"key":"Vs","display_name":"Screen Voltage (typical)","value":"250","numeric_value":"250","unit":"V","param_group":"typical_operating"},{"key":"Vg","display_name":"Grid 1 Bias Voltage","value":"-14","numeric_value":"-14","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"93","numeric_value":"93","unit":"mA","param_group":"typical_operating"},{"key":"mAs","display_name":"Screen Current","value":"6","numeric_value":"6","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"37500","numeric_value":"37500","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"8.3","numeric_value":"8.3","unit":"mA/V","param_group":"typical_operating"},{"key":"Pout","display_name":"Output Power","value":"10.5","numeric_value":"10.5","unit":"W","param_group":"output"},{"key":"rl","display_name":"Load Impedance","value":"2000","numeric_value":"2000","unit":"Ω","param_group":"output"},{"key":"Cgp","display_name":"Grid-to-Plate Capacitance","value":"0.5","numeric_value":"0.5","unit":"pF","param_group":"capacitances"},{"key":"Cin","display_name":"Input Capacitance","value":"16","numeric_value":"16","unit":"pF","param_group":"capacitances"},{"key":"Cout","display_name":"Output Capacitance","value":"8","numeric_value":"8","unit":"pF","param_group":"capacitances"}]},{"section_number":2,"section_label":"Triode Strapped","tube_type_key":"power_triode","specs":[{"key":"Va","display_name":"Anode Voltage (typical)","value":"250","numeric_value":"250","unit":"V","param_group":"typical_operating"},{"key":"Vg","display_name":"Grid 1 Bias Voltage","value":"-20","numeric_value":"-20","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"50","numeric_value":"50","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"1180","numeric_value":"1180","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"6.8","numeric_value":"6.8","unit":"mA/V","param_group":"typical_operating"},{"key":"mu","display_name":"Amplification Factor (μ)","value":"8","numeric_value":"8","unit":"—","param_group":"typical_operating"},{"key":"Rk","display_name":"Cathode Resistor (self-bias)","value":"350","numeric_value":"350","unit":"Ω","param_group":"typical_operating"},{"key":"Pout","display_name":"Output Power","value":"1.5","numeric_value":"1.5","unit":"W","param_group":"output"},{"key":"rl","display_name":"Load Impedance","value":"6000","numeric_value":"6000","unit":"Ω","param_group":"output"}]}],"synced_at":"2026-04-07T19:01:14.346Z"}