{"type_number":"25BK5","canonical_url":"https://tubeofile.com/tubes/25BK5","manufacturer":null,"tube_type_key":"beam_tetrode","tube_type_display_name":"Beam Tetrode","base_name":"Noval","description":"Beam power amplifier designed for audio-frequency power output service in AC/DC receivers with series-string heater circuits. 25V heater version related to the 350B beam tetrode family. Noval (B9A) base.","is_directly_heated":false,"completeness":"medium","notes":["GE Essential Characteristics confirms: 25V/0.3A heater, Noval (9BQ) base, beam power amplifier, Pa_max=9W, Va_max=250V, Vs_max=250V.","GE data: Va=250V, Vs=250V, Vg=5V (cathode bias), Ia=35mA, Is=3.5mA, ra=100k ohms, gm=8500 umhos.","Designed for series-string heater circuits in AC/DC consumer receivers where 25V heater segments are used.","The 25V/0.3A heater is standard for the 150 mA series-string heater chain used in many AC/DC TV and radio receivers."],"references":["https://tdsl.duncanamps.com/show.php?des=25BK5","https://www.radiomuseum.org/tubes/?tube=25BK5"],"source_urls":{"r_type":null,"tdsl":"https://tdsl.duncanamps.com/show.php?des=25BK5","radiomuseum":"https://www.radiomuseum.org/tubes/tube_25bk5.html"},"raw_equivalents":[],"equivalents":[],"similar":[{"type_number":"350B","reason":"Similar beam tetrode but Octal base with 6.3V heater — different base, different heater requirements","has_detail_page":true},{"type_number":"6L6","reason":"Similar beam tetrode class but Octal base and 6.3V heater — different base and heater","has_detail_page":true}],"pins":[{"pin_number":"1","function":"Control Grid (g1)","function_code":"g1","notes":null},{"pin_number":"2","function":"Cathode","function_code":"k","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":"Anode (Plate)","function_code":"a","notes":null},{"pin_number":"6","function":"No Connection","function_code":"nc","notes":null},{"pin_number":"7","function":"Screen Grid (g2)","function_code":"g2","notes":null},{"pin_number":"8","function":"No Connection","function_code":"nc","notes":null},{"pin_number":"9","function":"No Connection","function_code":"nc","notes":null}],"specs":[{"key":"Vh","display_name":"Heater Voltage","value":"25","numeric_value":"25","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":"Beam Tetrode","tube_type_key":"beam_tetrode","specs":[{"key":"Va_max","display_name":"Anode Voltage (max)","value":"250","numeric_value":"250","unit":"V","param_group":"absolute_max"},{"key":"Vs_max","display_name":"Screen Voltage (max)","value":"250","numeric_value":"250","unit":"V","param_group":"absolute_max"},{"key":"Pa_max","display_name":"Anode Dissipation (max)","value":"9","numeric_value":"9","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":"Vs","display_name":"Screen Voltage (typical)","value":"250","numeric_value":"250","unit":"V","param_group":"typical_operating"},{"key":"Vg","display_name":"Grid 1 Bias Voltage","value":"5","numeric_value":"5","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"35","numeric_value":"35","unit":"mA","param_group":"typical_operating"},{"key":"mAs","display_name":"Screen Current","value":"3.5","numeric_value":"3.5","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"100000","numeric_value":"100000","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"8.5","numeric_value":"8.5","unit":"mA/V","param_group":"typical_operating"}]}],"synced_at":"2026-04-07T12:07:48.826Z"}