{"type_number":"6S4A","canonical_url":"https://tubeofile.com/tubes/6S4A","manufacturer":"Tung-Sol","tube_type_key":"small_signal_triode","tube_type_display_name":"Small Signal Triode","base_name":"Noval","description":"Medium-mu triode in small-button 9-pin miniature construction with coated unipotential cathode. Designed for 600 mA series heater operation as a vertical deflection amplifier in television receivers. Heater thermal characteristics are controlled for warm-up surge minimisation. Electrically identical to the 6S4 except for controlled heater thermal characteristics.","is_directly_heated":false,"completeness":"high","notes":["6S4A is identical to 6S4 electrically; only heater thermal characteristics differ (controlled warm-up time). TDSL lists 6S4 as a 'different rating or performance' substitute.","Base is Small-Button Noval 9-Pin (JEDEC No. E9-1), basing designation 9AC. Pins 1, 7, and 8 are internal connections — do not use.","Philips interchange guide lists 6S4 -> 6S4A and 6S4A -> 6S4A (self-replacement).","MIL-HDBK-213A classifies as 'Receiving triode, miniature' and cross-references 6S4A as an other number for 6S4.","Brans Vademecum table IIIf lists 6S4 with equivalents 6BJ8 and 7AU7.","GE Essential Characteristics lists a max plate dissipation of 7.5 W for the 6S4; the Tung-Sol and RCA datasheets for 6S4A specify 8.5 W. The datasheet value of 8.5 W is used here.","The peak positive plate voltage rating of 2200 V reflects vertical-deflection service where flyback pulses are present.","Heater warm-up time is 11 seconds (defined as time to reach 80% of rated voltage across heater in a specified test circuit)."],"references":["https://frank.pocnet.net/sheets/127/6/6S4A.pdf","https://frank.pocnet.net/sheets/049/6/6S4A.pdf","https://frank.pocnet.net/sheets/093/6/6S4A.pdf"],"source_urls":{"r_type":null,"tdsl":"https://tdsl.duncanamps.com/show.php?des=6S4A","radiomuseum":"https://www.radiomuseum.org/tubes/tube_6s4a.html"},"raw_equivalents":["6S4"],"equivalents":[],"similar":[],"pins":[{"pin_number":"1","function":"Internal Connection","function_code":"ic","notes":null},{"pin_number":"2","function":"Cathode","function_code":"k","notes":null},{"pin_number":"3","function":"Grid","function_code":"g1","notes":null},{"pin_number":"4","function":"Heater","function_code":"h","notes":null},{"pin_number":"5","function":"Heater","function_code":"h","notes":null},{"pin_number":"6","function":"Grid","function_code":"g1","notes":null},{"pin_number":"7","function":"Internal Connection","function_code":"ic","notes":null},{"pin_number":"8","function":"Internal Connection","function_code":"ic","notes":null},{"pin_number":"9","function":"Plate","function_code":"a","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":"0.6","numeric_value":"0.6","unit":"A","param_group":"heater"}],"sections":[{"section_number":1,"section_label":"Medium-Mu Triode","tube_type_key":"small_signal_triode","specs":[{"key":"Va_max","display_name":"Anode Voltage (max)","value":"550","numeric_value":"550","unit":"V","param_group":"absolute_max"},{"key":"Va_peak_max","display_name":"Peak Anode Voltage (max)","value":"2200","numeric_value":"2200","unit":"V","param_group":"absolute_max"},{"key":"Pa_max","display_name":"Anode Dissipation (max)","value":"8.5","numeric_value":"8.5","unit":"W","param_group":"absolute_max"},{"key":"Ik_max","display_name":"Cathode Current (max)","value":"30","numeric_value":"30","unit":"mA","param_group":"absolute_max"},{"key":"Vhk_max","display_name":"Heater-to-Cathode Voltage (max)","value":"200","numeric_value":"200","unit":"V","param_group":"absolute_max"},{"key":"Rg_max","display_name":"Max Grid Resistor","value":"2.2","numeric_value":"2.2","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":"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":"24","numeric_value":"24","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"3700","numeric_value":"3700","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"4.5","numeric_value":"4.5","unit":"mA/V","param_group":"typical_operating"},{"key":"mu","display_name":"Amplification Factor (μ)","value":"16.5","numeric_value":"16.5","unit":"—","param_group":"typical_operating"},{"key":"Cgp","display_name":"Grid-to-Plate Capacitance","value":"2.4","numeric_value":"2.4","unit":"pF","param_group":"capacitances"},{"key":"Cgk","display_name":"Grid-to-Cathode Capacitance","value":"4.2","numeric_value":"4.2","unit":"pF","param_group":"capacitances"},{"key":"Cout","display_name":"Output Capacitance","value":"0.6","numeric_value":"0.6","unit":"pF","param_group":"capacitances"}]}],"synced_at":"2026-04-07T12:28:35.661Z"}