{"type_number":"ML6","canonical_url":"https://tubeofile.com/tubes/ML6","manufacturer":"M-O Valve Co. (Marconi-Osram)","tube_type_key":"small_signal_triode","tube_type_display_name":"Small Signal Triode","base_name":"B5B","description":"British indirectly-heated LF amplifying triode by M-O Valve Co. (Marconi-Osram). 6.3 V heater version of the ML4, adapted for operation in equipment powered from vehicle batteries. Widely used by the Royal Air Force as an RF oscillator in medium-sized military transmitters during WWII.","is_directly_heated":false,"completeness":"high","notes":["ML6 is the 6.3 V vehicle-battery version of the ML4 (4 V mains-heater version). Same envelope, same B5 5-pin base, same triode structure and electrical characteristics; only the heater rating differs.","British military / RAF designations: CV1105 (joint-services CV number), VR105 (Air Ministry 'Valve Receiving' designation), VT105 (RAF Type code). The ceramic-base wartime variant is sometimes marked ML6C.","Used during WWII as an RF oscillator in medium-sized military transmitters (per The Valve Museum / r-type.org).","Anode dissipation rating: the ML4 datasheet states the valve can be allowed to dissipate the equivalent of 5 W in transmitter / oscillator service; this same rating applies to the ML6.","Pin functions on the B5 base: 1 = Anode, 2 = Grid, 3 = Heater, 4 = Heater, 5 = Cathode (per the Osram ML4 datasheet, which the ML6 inherits).","Triode physics check: gm × ra / 1000 = 3.8 × 3700 / 1000 = 14.06 ≈ mu (the Valve Museum lists no separate mu value; the implied amplification factor is approximately 14, consistent with the ML4 family).","Capacitances are taken from the ML4 datasheet (the ML6 datasheet was not located separately): Cga ≈ 6.3 pF, Ca-others ≈ 4.5 pF, Cg-others ≈ 7.2 pF.","Brans Vade Mecum lists ML6 in table IIIa (small-signal triodes) with equivalents CV1105, D105."],"references":["https://www.r-type.org/exhib/aac0035.htm","https://www.r-type.org/pdfs/ml4.pdf","https://tdsl.duncanamps.com/show.php?des=ML6"],"source_urls":{"r_type":"https://www.r-type.org/exhib/aac0035.htm","tdsl":"https://tdsl.duncanamps.com/show.php?des=ML6","radiomuseum":null},"raw_equivalents":["CV1105","VR105","VT105","D105","ML4"],"equivalents":[],"similar":[],"pins":[{"pin_number":"1","function":"Anode","function_code":"a","notes":null},{"pin_number":"2","function":"Control Grid","function_code":"g1","notes":null},{"pin_number":"3","function":"Heater","function_code":"h","notes":null},{"pin_number":"4","function":"Heater","function_code":"h","notes":null},{"pin_number":"5","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":"Triode","tube_type_key":"small_signal_triode","specs":[{"key":"Va_max","display_name":"Anode Voltage (max)","value":"250","numeric_value":"250","unit":"V","param_group":"absolute_max"},{"key":"Pa_max","display_name":"Anode Dissipation (max)","value":"5","numeric_value":"5","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":"-13.5","numeric_value":"-13.5","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"25","numeric_value":"25","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":"3.8","numeric_value":"3.8","unit":"mA/V","param_group":"typical_operating"},{"key":"mu","display_name":"Amplification Factor (μ)","value":"14","numeric_value":"14","unit":"—","param_group":"typical_operating"},{"key":"Pout","display_name":"Output Power","value":"0.65","numeric_value":"0.65","unit":"W","param_group":"output"},{"key":"Cgp","display_name":"Grid-to-Plate Capacitance","value":"6.3","numeric_value":"6.3","unit":"pF","param_group":"capacitances"},{"key":null,"display_name":"Grid-to-others Capacitance","value":"7.2","numeric_value":"7.2","unit":"pF","param_group":null},{"key":null,"display_name":"Anode-to-others Capacitance","value":"4.5","numeric_value":"4.5","unit":"pF","param_group":null}]}],"synced_at":"2026-04-08T06:03:42.494Z"}