{"type_number":"7A7","canonical_url":"https://tubeofile.com/tubes/7A7","manufacturer":"Tung-Sol","tube_type_key":"ss_pentode","tube_type_display_name":"Small Signal Pentode","base_name":"Loctal","description":"Remote-cutoff RF pentode in loctal (lock-in) construction, designed for use as an RF or IF amplifier in AC/DC receivers. Electrically similar to the 6SK7 but in the loctal envelope. Manufactured by Tung-Sol, introduced 1938. Characterized by variable-mu grid for automatic gain control applications.","is_directly_heated":false,"completeness":"medium","notes":["Remote-cutoff (variable-mu) pentode — grid #1 has variable pitch winding for gradual gain control.","Tung-Sol datasheet specifies two typical operating conditions: Va=300V/Vg2=100V and Va=100V/Vg2=100V.","GE lists plate current 9.2 mA and gm 2000 umhos at Va=250V, Vg2=100V; Tung-Sol datasheet shows 13 mA / 2350 umhos at Va=300V and 9.2 mA / 2000 umhos at Va=250V.","Grid #1 cutoff voltage approximately -35V.","14A7 is the 12.6V heater series equivalent (same as 12B7)."],"references":["https://frank.pocnet.net/sheets/127/7/7A7.pdf"],"source_urls":{"r_type":null,"tdsl":"https://tdsl.duncanamps.com/show.php?des=7A7","radiomuseum":"https://www.radiomuseum.org/tubes/tube_7a7.html"},"raw_equivalents":["14A7","12B7","CV877"],"equivalents":[],"similar":[{"type_number":"6SK7","reason":"Electrically similar remote-cutoff pentode but Octal base — not pin-compatible with Loctal","has_detail_page":true},{"type_number":"7B7","reason":"Same Loctal pinout (8V) and remote-cutoff pentode, but different heater current (0.15A vs 0.3A) and different gm/rp — Raytheon lists as substitute but verify operating point","has_detail_page":true},{"type_number":"7C7","reason":"Same Loctal pinout but sharp-cutoff pentode — different grid characteristic, not suitable for AGC service","has_detail_page":true}],"pins":[{"pin_number":"1","function":"Heater","function_code":"h","notes":null},{"pin_number":"2","function":"Plate","function_code":"a","notes":null},{"pin_number":"3","function":"Screen Grid (g2)","function_code":"g2","notes":null},{"pin_number":"4","function":"Grid #3 and #5 (Suppressor)","function_code":"g3","notes":null},{"pin_number":"5","function":"Grid #4 (connected to pin #4 internally)","function_code":"g3","notes":null},{"pin_number":"6","function":"Control Grid (g1)","function_code":"g1","notes":null},{"pin_number":"7","function":"Cathode","function_code":"k","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":"Remote-Cutoff Pentode","tube_type_key":"ss_pentode","specs":[{"key":"Va_max","display_name":"Anode Voltage (max)","value":"300","numeric_value":"300","unit":"V","param_group":"absolute_max"},{"key":"Vg2_max","display_name":"Screen Voltage (max)","value":"125","numeric_value":"125","unit":"V","param_group":"absolute_max"},{"key":"Pa_max","display_name":"Anode Dissipation (max)","value":"4","numeric_value":"4","unit":"W","param_group":"absolute_max"},{"key":"Pg2_max","display_name":"Screen Dissipation (max)","value":"0.4","numeric_value":"0.4","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":"300","numeric_value":"300","unit":"V","param_group":"typical_operating"},{"key":"Vg","display_name":"Grid 1 Bias Voltage","value":"-1","numeric_value":"-1","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"15","numeric_value":"15","unit":"mA","param_group":"typical_operating"},{"key":"Vg2","display_name":"Screen Voltage","value":"100","numeric_value":"100","unit":"V","param_group":"typical_operating"},{"key":"mAg2","display_name":"Screen Current","value":"4","numeric_value":"4","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"120000","numeric_value":"120000","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"2.35","numeric_value":"2.35","unit":"mA/V","param_group":"typical_operating"},{"key":"Cgp","display_name":"Grid-to-Plate Capacitance","value":"0.003","numeric_value":"0.003","unit":"pF","param_group":"capacitances"},{"key":"Cin","display_name":"Input Capacitance","value":"6","numeric_value":"6","unit":"pF","param_group":"capacitances"},{"key":"Cout","display_name":"Output Capacitance","value":"7","numeric_value":"7","unit":"pF","param_group":"capacitances"}]}],"synced_at":"2026-04-07T12:31:43.058Z"}