{"type_number":"RV218","canonical_url":"https://tubeofile.com/tubes/RV218","manufacturer":"Telefunken","tube_type_key":"power_triode","tube_type_display_name":"Power Triode","base_name":"B4","description":"Kraftverstärker-Röhre — directly heated power triode for audio and transmitter amplifier service","is_directly_heated":true,"completeness":"medium","notes":["Filament voltage stated as 7.5 V in the RV218 Telefunken datasheet; the RV258 datasheet (same book, adjacent page) states 7.0 V for the identical tube. Reference indexes list 7.2 V. The discrepancy likely reflects rounding — both tubes operate from the same nominal ~7 V filament supply.","Maximum ratings are Va=440V and Pa=24W. The datasheet explicitly states that for higher loadings (Va >440V or Pa >24W), the RV218 must be replaced by the RV258.","Extensively used in transmitter service. When paralleling multiple tubes, the datasheet warns of a risk of self-oscillation at ultra-short (UHF) wavelengths.","A special grid construction prevents 'Durchstoßen' (grid emission / secondary emission breakthrough), a known failure mode in early DHT power triodes.","Amplification factor mu = 1/D = 1/0.14 ≈ 7; anode resistance ra derived as mu/gm = 7/0.002 = 3500 Ω (not explicitly stated in datasheet).","Codewort (factory test code): nsyit."],"references":["https://frank.yueksel.org/sheets/105/r/RV218.pdf","https://www.radiomuseum.org/tubes/tube_rv218.html"],"source_urls":{"r_type":null,"tdsl":"https://tdsl.duncanamps.com/show.php?des=RV218","radiomuseum":"https://www.radiomuseum.org/tubes/tube_rv218.html"},"raw_equivalents":["RV258"],"equivalents":[{"type_number":"RV258","equivalence_type":"direct","notes":null}],"similar":[{"type_number":"P20","reason":"Same B4 base and 7.2V heater DHT triode, listed as similar with differences — pin functions require verification before substitution","has_detail_page":false}],"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":"7.5","numeric_value":"7.5","unit":"V","param_group":"heater"},{"key":"Ah","display_name":"Heater Current","value":"1.1","numeric_value":"1.1","unit":"A","param_group":"heater"}],"sections":[{"section_number":1,"section_label":"Triode","tube_type_key":"power_triode","specs":[{"key":"Va_max","display_name":"Anode Voltage (max)","value":"440","numeric_value":"440","unit":"V","param_group":"absolute_max"},{"key":"Pa_max","display_name":"Anode Dissipation (max)","value":"24","numeric_value":"24","unit":"W","param_group":"absolute_max"},{"key":"Va","display_name":"Anode Voltage (typical)","value":"350","numeric_value":"350","unit":"V","param_group":"typical_operating"},{"key":"Vg","display_name":"Grid 1 Bias Voltage","value":"-19","numeric_value":"-19","unit":"V","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"3500","numeric_value":"3500","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"2.0","numeric_value":"2","unit":"mA/V","param_group":"typical_operating"},{"key":"mu","display_name":"Amplification Factor (μ)","value":"7","numeric_value":"7","unit":"—","param_group":"typical_operating"},{"key":"Pout","display_name":"Output Power","value":"2.5","numeric_value":"2.5","unit":"W","param_group":"output"}]}],"synced_at":"2026-04-07T12:51:54.253Z"}