{"type_number":"6A8","canonical_url":"https://tubeofile.com/tubes/6A8","manufacturer":"RCA","tube_type_key":"hexode","tube_type_display_name":"Hexode","base_name":"Octal","description":"Pentagrid converter (heptode) in metal or glass envelope with Octal base, designed for combined oscillator-mixer service in superheterodyne radio receivers. One of the earliest pentagrid converters, introduced August 1935. Widely used in consumer radio equipment through the 1950s with over 3000 documented receiver models.","is_directly_heated":false,"completeness":"high","notes":["The 6A8 uses a top-cap connection for grid #1 (oscillator grid) — requires clip lead.","GE data shows identical specs for 6A8, 6A8-G, and 6A8-GT variants.","Sams lists substitutes: PH4, X63, 19SU.","Conversion transconductance 550 umhos at Va=250V, Vg2=100V, Vg1=-3V.","Max plate dissipation 1W, max anode voltage 300V, max screen voltage 100V."],"references":["https://tdsl.duncanamps.com/show.php?des=6A8","https://www.radiomuseum.org/tubes/?tube=6A8"],"source_urls":{"r_type":null,"tdsl":"https://tdsl.duncanamps.com/show.php?des=6A8","radiomuseum":"https://www.radiomuseum.org/tubes/tube_6a8.html"},"raw_equivalents":["6A8G","6A8GT","CV579","VT151"],"equivalents":[],"similar":[{"type_number":"6BE6","reason":"Miniature (B7G) successor pentagrid converter — electrically similar but different base","has_detail_page":true},{"type_number":"6SA7","reason":"Improved pentagrid converter successor with better conversion gain — different pinout, not a drop-in","has_detail_page":true},{"type_number":"7B8","reason":"Loctal version of the pentagrid converter family — similar function but different base","has_detail_page":false}],"pins":[{"pin_number":"1","function":"Shell (Metal) / No Connection (Glass)","function_code":"nc","notes":null},{"pin_number":"2","function":"Plate","function_code":"a","notes":null},{"pin_number":"3","function":"Grids 3 & 5 (Screen)","function_code":"g2","notes":null},{"pin_number":"4","function":"Grids 2 & 4 (Oscillator Anode)","function_code":"g2_osc","notes":null},{"pin_number":"5","function":"Grid 1 (Oscillator Grid)","function_code":"g1","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":"Grid 4 (Signal Grid)","function_code":"g4","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":"Pentagrid Converter","tube_type_key":"hexode","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":"100","numeric_value":"100","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":"Pg2_max","display_name":"Screen Dissipation (max)","value":"0.3","numeric_value":"0.3","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":"-3","numeric_value":"-3","unit":"V","param_group":"typical_operating"},{"key":"Vg2","display_name":"Screen Voltage","value":"100","numeric_value":"100","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"3.5","numeric_value":"3.5","unit":"mA","param_group":"typical_operating"},{"key":"mAg2","display_name":"Screen Current","value":"2.7","numeric_value":"2.7","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"360000","numeric_value":"360000","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"0.55","numeric_value":"0.55","unit":"mA/V","param_group":"typical_operating"}]}],"synced_at":"2026-04-07T12:14:42.013Z"}