{"type_number":"12J7GT","canonical_url":"https://tubeofile.com/tubes/12J7GT","manufacturer":null,"tube_type_key":"ss_pentode","tube_type_display_name":"Small Signal Pentode","base_name":"Octal","description":"Sharp-cutoff pentode for use as RF amplifier, IF amplifier, detector, or audio voltage amplifier. 12.6V heater version of the 6J7, with top-cap control grid connection. Octal base.","is_directly_heated":false,"completeness":"high","notes":["12.6V heater version of the 6J7. Heater current is 0.15A at 12.6V (vs 0.3A at 6.3V for the 6J7).","Raytheon data confirms: 12.6V/0.15A heater, pentode design, Va=250V, Vg=-3V, Vs=100V, Ia=2.0mA, gm=1225 umhos, ra=1.5 MOhm.","The control grid (g1) is brought out to a top cap, not to a base pin.","Brans Vademecum lists CV917 as equivalent.","The grid circuit DC resistance should not exceed 1.0 megohm under rated maximum conditions."],"references":["https://frank.pocnet.net/sheets/093/6/6J7.pdf"],"source_urls":{"r_type":null,"tdsl":"https://tdsl.duncanamps.com/show.php?des=12J7GT","radiomuseum":"https://www.radiomuseum.org/tubes/tube_12j7gt.html"},"raw_equivalents":["CV917"],"equivalents":[],"similar":[{"type_number":"6C6","reason":"Electrically identical predecessor but uses 6-pin UX6 base and 6.3V heater","has_detail_page":true},{"type_number":"6J7","reason":"Electrically identical but 6.3V/0.3A heater — not a drop-in in 12.6V heater circuits","has_detail_page":true},{"type_number":"6SJ7","reason":"Successor with identical electricals but control grid moved from top cap to pin 4 and 6.3V heater — different pin topology and heater","has_detail_page":true}],"pins":[{"pin_number":"1","function":"Shell and Internal Shield","function_code":"ia","notes":null},{"pin_number":"2","function":"Heater","function_code":"h","notes":null},{"pin_number":"3","function":"Plate (Anode)","function_code":"a","notes":null},{"pin_number":"4","function":"Screen Grid","function_code":"g2","notes":null},{"pin_number":"5","function":"Suppressor Grid","function_code":"g3","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},{"pin_number":"TC","function":"Control Grid","function_code":"g1","notes":null}],"specs":[{"key":"Vh","display_name":"Heater 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(max)","value":"90","numeric_value":"90","unit":"V","param_group":"absolute_max"},{"key":"Rg_max","display_name":"Max Grid Resistor","value":"1","numeric_value":"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":"100","numeric_value":"100","unit":"V","param_group":"typical_operating"},{"key":"Vg","display_name":"Grid 1 Bias Voltage","value":"-3","numeric_value":"-3","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"2.0","numeric_value":"2","unit":"mA","param_group":"typical_operating"},{"key":"mAs","display_name":"Screen Current","value":"0.5","numeric_value":"0.5","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode 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(max)","value":"250","numeric_value":"250","unit":"V","param_group":"absolute_max"},{"key":"Pa_max","display_name":"Anode Dissipation (max)","value":"1.75","numeric_value":"1.75","unit":"W","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":"-8","numeric_value":"-8","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"6.5","numeric_value":"6.5","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"10500","numeric_value":"10500","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"1.9","numeric_value":"1.9","unit":"mA/V","param_group":"typical_operating"},{"key":"mu","display_name":"Amplification Factor (μ)","value":"20","numeric_value":"20","unit":"—","param_group":"typical_operating"},{"key":"Cgp","display_name":"Grid-to-Plate Capacitance","value":"2.0","numeric_value":"2","unit":"pF","param_group":"capacitances"},{"key":"Cgk","display_name":"Grid-to-Cathode Capacitance","value":"5","numeric_value":"5","unit":"pF","param_group":"capacitances"},{"key":"Cak","display_name":"Anode-to-Cathode Capacitance","value":"14","numeric_value":"14","unit":"pF","param_group":"capacitances"}]}],"synced_at":"2026-04-07T12:05:26.230Z"}