{"type_number":"6F6S","canonical_url":"https://tubeofile.com/tubes/6F6S","manufacturer":null,"tube_type_key":"power_pentode","tube_type_display_name":"Power Pentode","base_name":"Octal","description":"Soviet power pentode (6Ф6С) for AF output stages. Direct equivalent of the Western 6F6GT. Octal base, glass envelope, indirectly heated. Can be operated in pentode or triode connection. Widely used in Soviet broadcast receivers and public address systems.","is_directly_heated":false,"completeness":"high","notes":["Cyrillic designation: 6Ф6С. Russian_equivalents.json confirms: 6F6S ≈ 6F6GT.","From Tung-Sol datasheet: pentode connection at Va=250V, Vs=250V: Ia=34mA, gm=2500 µmhos, ra=80kΩ, Pout=3.2W. Triode connection at Va=250V: Ia=31mA, gm=2600 µmhos, ra=2600Ω.","Maximum ratings (pentode): Va_max=375V, Vs_max=285V, Pa_max=11W, Ps_max=3.75W.","Grid resistor: max 0.5MΩ for self-bias, 0.1MΩ for fixed bias.","The 6F6/6F6GT/G, 2A5, and 42 are all pentode power amplifiers with identical electrical characteristics — only heater and base differ."],"references":["https://frank.pocnet.net/sheets/127/6/6F6.pdf","https://www.radiomuseum.org/tubes/tube_6f6s.html"],"source_urls":{"r_type":null,"tdsl":null,"radiomuseum":"https://www.radiomuseum.org/tubes/tube_6f6s.html"},"raw_equivalents":["6F6","6F6GT","6F6G","CV1542","VT-66","6F6M"],"equivalents":[{"type_number":"6F6","equivalence_type":"direct","notes":null}],"similar":[{"type_number":"2A5","reason":"Same electricals but UX6 base (6-pin) — not pin-compatible","has_detail_page":false},{"type_number":"42","reason":"Same electricals as 2A5/6F6 but UX6 base with different heater (6.3V, 0.7A)","has_detail_page":false},{"type_number":"6P6S","reason":"Soviet 6V6 equivalent — beam tetrode vs pentode, different operating characteristics","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","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","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":"0.7","numeric_value":"0.7","unit":"A","param_group":"heater"}],"sections":[{"section_number":1,"section_label":"Pentode","tube_type_key":"power_pentode","specs":[{"key":"Va_max","display_name":"Anode Voltage (max)","value":"375","numeric_value":"375","unit":"V","param_group":"absolute_max"},{"key":"Vs_max","display_name":"Screen Voltage (max)","value":"285","numeric_value":"285","unit":"V","param_group":"absolute_max"},{"key":"Pa_max","display_name":"Anode Dissipation (max)","value":"11","numeric_value":"11","unit":"W","param_group":"absolute_max"},{"key":"Ps_max","display_name":"Screen Dissipation (max)","value":"3.75","numeric_value":"3.75","unit":"W","param_group":"absolute_max"},{"key":"Rg_max","display_name":"Max Grid Resistor","value":"0.5","numeric_value":"0.5","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":"-16.5","numeric_value":"-16.5","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"34","numeric_value":"34","unit":"mA","param_group":"typical_operating"},{"key":"mAs","display_name":"Screen Current","value":"6.5","numeric_value":"6.5","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"80000","numeric_value":"80000","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"2.5","numeric_value":"2.5","unit":"mA/V","param_group":"typical_operating"},{"key":"Pout","display_name":"Output Power","value":"3.2","numeric_value":"3.2","unit":"W","param_group":"output"},{"key":"rl","display_name":"Load Impedance","value":"7000","numeric_value":"7000","unit":"Ω","param_group":"output"}]},{"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":"31","numeric_value":"31","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"2600","numeric_value":"2600","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"2.6","numeric_value":"2.6","unit":"mA/V","param_group":"typical_operating"},{"key":"Pout","display_name":"Output Power","value":"0.85","numeric_value":"0.85","unit":"W","param_group":"output"}]}],"synced_at":"2026-04-21T23:07:43.349Z"}