{"type_number":"UCH81","canonical_url":"https://tubeofile.com/tubes/UCH81","manufacturer":"Philips","tube_type_key":"triode_hexode","tube_type_display_name":"Triode-Hexode","base_name":"Noval","description":"Triode-heptode frequency converter for superheterodyne radio receivers. Noval (B9A) base. Series-heater type with 19 V / 100 mA heater for AC/DC receivers. The 'U' prefix indicates a series-heater tube in the Philips naming convention. Same pinout as ECH81.","is_directly_heated":false,"completeness":"high","notes":["Series-heater design (100 mA) for AC/DC receivers without heater transformer.","The 'U' prefix indicates 100 mA series-heater operation.","Triode and heptode sections share a common cathode.","Heptode conversion conductance Sc = 620 uA/V at Vb=100V, 750 uA/V at Vb=170V.","Brans lists equivalents: 19AJ8, 19D8, 10C14, X119."],"references":["https://frank.pocnet.net/sheets/050/u/UCH81.pdf"],"source_urls":{"r_type":null,"tdsl":"https://tdsl.duncanamps.com/show.php?des=UCH81","radiomuseum":"https://www.radiomuseum.org/tubes/tube_uch81.html"},"raw_equivalents":["X119","19AJ8"],"equivalents":[{"type_number":"19AJ8","equivalence_type":"direct","notes":null}],"similar":[{"type_number":"ECH81","reason":"6.3 V heater version — same Noval base and pinout but different heater voltage","has_detail_page":true},{"type_number":"ECH83","reason":"Reportedly identical internally to ECH81 — same base and pinout","has_detail_page":true},{"type_number":"HCH81","reason":"12.6 V heater version — same pinout but different heater voltage","has_detail_page":true}],"pins":[{"pin_number":"1","function":"Heptode Anode","function_code":"a2","notes":null},{"pin_number":"2","function":"Heptode Screen Grid (g2+g4)","function_code":"g2","notes":null},{"pin_number":"3","function":"Common Cathode, Suppressor Grid (g5)","function_code":"k","notes":null},{"pin_number":"4","function":"Heater","function_code":"h","notes":null},{"pin_number":"5","function":"Heater","function_code":"h","notes":null},{"pin_number":"6","function":"Triode Anode","function_code":"a1","notes":null},{"pin_number":"7","function":"Heptode Signal Grid (g1)","function_code":"g1","notes":null},{"pin_number":"8","function":"Triode Grid / Heptode Oscillator Grid (g3)","function_code":"g3","notes":null},{"pin_number":"9","function":"Internal shield","function_code":"ia","notes":null}],"specs":[{"key":"Vh","display_name":"Heater Voltage","value":"19","numeric_value":"19","unit":"V","param_group":"heater"},{"key":"Ah","display_name":"Heater Current","value":"0.1","numeric_value":"0.1","unit":"A","param_group":"heater"}],"sections":[{"section_number":1,"section_label":"Triode (Oscillator)","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":"0.8","numeric_value":"0.8","unit":"W","param_group":"absolute_max"},{"key":"Ik_max","display_name":"Cathode Current (max)","value":"6.5","numeric_value":"6.5","unit":"mA","param_group":"absolute_max"},{"key":"Rg_max","display_name":"Max Grid Resistor","value":"3","numeric_value":"3","unit":"MΩ","param_group":"absolute_max"},{"key":"Va","display_name":"Anode Voltage (typical)","value":"100","numeric_value":"100","unit":"V","param_group":"typical_operating"},{"key":"Vg","display_name":"Grid 1 Bias Voltage","value":"-2","numeric_value":"-2","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"7.3","numeric_value":"7.3","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"7000","numeric_value":"7000","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"2.4","numeric_value":"2.4","unit":"mA/V","param_group":"typical_operating"},{"key":"mu","display_name":"Amplification Factor (μ)","value":"17","numeric_value":"17","unit":"—","param_group":"typical_operating"}]},{"section_number":2,"section_label":"Heptode (Mixer)","tube_type_key":"hexode","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 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Current","value":"3.2","numeric_value":"3.2","unit":"mA","param_group":"typical_operating"},{"key":"mAs","display_name":"Screen Current","value":"6.8","numeric_value":"6.8","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"900000","numeric_value":"900000","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"0.75","numeric_value":"0.75","unit":"mA/V","param_group":"typical_operating"},{"key":"Rk","display_name":"Cathode Resistor (self-bias)","value":"150","numeric_value":"150","unit":"Ω","param_group":"typical_operating"}]}],"synced_at":"2026-04-07T19:09:28.462Z"}