{"type_number":"RE084","canonical_url":"https://tubeofile.com/tubes/RE084","manufacturer":"Telefunken","tube_type_key":"small_signal_triode","tube_type_display_name":"Small Signal Triode","base_name":"B4","description":"Directly heated triode for battery-operated radio receivers. Low-power filament designed for battery supply at 4 V / 80 mA.","is_directly_heated":true,"completeness":"medium","notes":["Introduced by Telefunken circa 1927 for battery-powered receivers; filament designed for a 4 V battery supply.","Directly heated: the filament doubles as the cathode. Bias the negative filament end to set operating point.","Known equivalents: A408 (Valvo), A415 (Philips/RT), L409 (Zenith), KL70406 (Tungsram), LD410 (Tungsram) — all pin-for-pin compatible on the B4 base.","RE084k and RE084s are variants with slightly different filament or envelope construction but the same electrical characteristics and B4 base."],"references":["https://frank.pocnet.net/sheets/105/r/RE084.pdf","https://www.radiomuseum.org/tubes/tube_re084.html","http://vinylsavor.blogspot.com/2022/12/tube-of-month-re084.html"],"source_urls":{"r_type":null,"tdsl":"http://tdsl.duncanamps.com/show.php?des=RE084","radiomuseum":"https://www.radiomuseum.org/tubes/tube_re084.html"},"raw_equivalents":["A408","A415","L409","KL70406","LD410"],"equivalents":[],"similar":[],"pins":[{"pin_number":"1","function":"Filament (+)","function_code":"h","notes":null},{"pin_number":"2","function":"Anode","function_code":"a","notes":null},{"pin_number":"3","function":"Control Grid","function_code":"g1","notes":null},{"pin_number":"4","function":"Filament (−)","function_code":"h","notes":null}],"specs":[{"key":"Vh","display_name":"Heater Voltage","value":"4","numeric_value":"4","unit":"V","param_group":"heater"},{"key":"Ah","display_name":"Heater Current","value":"0.08","numeric_value":"0.08","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":"150","numeric_value":"150","unit":"V","param_group":"absolute_max"},{"key":"Va","display_name":"Anode Voltage (typical)","value":"100","numeric_value":"100","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"4","numeric_value":"4","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"10000","numeric_value":"10000","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"1.5","numeric_value":"1.5","unit":"mA/V","param_group":"typical_operating"},{"key":"mu","display_name":"Amplification Factor (μ)","value":"15","numeric_value":"15","unit":"—","param_group":"typical_operating"}]}],"synced_at":"2026-04-07T12:51:36.771Z"}