{"type_number":"7F7","canonical_url":"https://tubeofile.com/tubes/7F7","manufacturer":"Sylvania","tube_type_key":"small_signal_triode","tube_type_display_name":"Small Signal Triode","base_name":"Loctal","description":"High-mu double triode in Lock-In (Loktal) construction, designed for use as a resistance coupled amplifier or phase inverter. Electrically identical to the 6SL7GT.","is_directly_heated":false,"completeness":"high","notes":["Sylvania originally rated the heater at 7.0V nominal to accommodate lead-acid battery charging voltage in mobile equipment; Tung-Sol and later datasheets standardize at 6.3V. The heater is robust across this range.","Only Sylvania, Raytheon, and National Union manufactured Loktal tubes; other branded versions were typically rebranded Sylvania production.","Loktal pins are susceptible to corrosion — clean contacts are essential for reliable operation.","All elements except the common heater are brought out separately, allowing each triode section to operate independently.","The Sams Tube Substitution Handbook lists no drop-in substitutes for the 7F7, reflecting the limited adoption of the Loctal base format."],"references":["https://frank.pocnet.net/sheets/084/7/7F7.pdf","https://frank.pocnet.net/sheets/127/7/7F7.pdf"],"source_urls":{"r_type":null,"tdsl":"https://tdsl.duncanamps.com/show.php?des=7F7","radiomuseum":"https://www.radiomuseum.org/tubes/tube_7f7.html"},"raw_equivalents":["VT-189","CV893","14H7"],"equivalents":[],"similar":[{"type_number":"14F7","reason":"12.6V heater version of 7F7 with same Loctal base and pinout — requires different heater supply","has_detail_page":false},{"type_number":"6SL7GT","reason":"Electrically identical but uses Octal base — not pin-compatible with Loctal socket","has_detail_page":false}],"pins":[{"pin_number":"1","function":"Heater","function_code":"h","notes":null},{"pin_number":"2","function":"Cathode 1","function_code":"k1","notes":null},{"pin_number":"3","function":"Anode 1","function_code":"a1","notes":null},{"pin_number":"4","function":"Control Grid 1","function_code":"g1_1","notes":null},{"pin_number":"5","function":"Control Grid 2","function_code":"g1_2","notes":null},{"pin_number":"6","function":"Anode 2","function_code":"a2","notes":null},{"pin_number":"7","function":"Cathode 2","function_code":"k2","notes":null},{"pin_number":"8","function":"Heater","function_code":"h","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":"0.3","numeric_value":"0.3","unit":"A","param_group":"heater"}],"sections":[{"section_number":1,"section_label":"Triode","tube_type_key":"small_signal_triode","specs":[{"key":"Va_max","display_name":"Anode Voltage (max)","value":"300","numeric_value":"300","unit":"V","param_group":"absolute_max"},{"key":"Pa_max","display_name":"Anode Dissipation (max)","value":"1","numeric_value":"1","unit":"W","param_group":"absolute_max"},{"key":"Vhk_max","display_name":"Heater-to-Cathode Voltage (max)","value":"90","numeric_value":"90","unit":"V","param_group":"absolute_max"},{"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":"-2","numeric_value":"-2","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"2.3","numeric_value":"2.3","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"44000","numeric_value":"44000","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"1.6","numeric_value":"1.6","unit":"mA/V","param_group":"typical_operating"},{"key":"mu","display_name":"Amplification Factor (μ)","value":"70","numeric_value":"70","unit":"—","param_group":"typical_operating"},{"key":"Cgp","display_name":"Grid-to-Plate Capacitance","value":"1.6","numeric_value":"1.6","unit":"pF","param_group":"capacitances"},{"key":"Cin","display_name":"Input Capacitance","value":"2.4","numeric_value":"2.4","unit":"pF","param_group":"capacitances"},{"key":"Cout","display_name":"Output Capacitance","value":"2.0","numeric_value":"2","unit":"pF","param_group":"capacitances"}]}],"synced_at":"2026-04-07T19:05:31.871Z"}