{"type_number":"HCH81","canonical_url":"https://tubeofile.com/tubes/HCH81","manufacturer":"Philips","tube_type_key":"triode_hexode","tube_type_display_name":"Triode-Hexode","base_name":"Noval","description":"Triode-heptode frequency converter for use in AM, FM, and AM/FM receivers. Noval (B9A) base. Heater voltage 12.6 V at 150 mA, suitable for series or parallel supply. Philips design. Same pinout as ECH81/UCH81 but with 12.6 V heater.","is_directly_heated":false,"completeness":"high","notes":["The 'H' prefix in the Mullard/Philips naming convention indicates a 12.6 V heater tube.","Tentative/preliminary data (Vorlaufige Daten) per original Philips datasheet.","Triode and heptode sections share a common cathode.","Sams substitution guide lists 12AJ7 as substitute.","Brans lists equivalents: 12AJ8, 19AJ8, 19D8, 10C14, 6AJ8, 6C12, ECH81."],"references":["https://frank.pocnet.net/sheets/030/h/HCH81.pdf"],"source_urls":{"r_type":null,"tdsl":null,"radiomuseum":"https://www.radiomuseum.org/tubes/tube_hch81.html"},"raw_equivalents":["12AJ8"],"equivalents":[],"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":"UCH81","reason":"19 V / 100 mA series-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":"12.6","numeric_value":"12.6","unit":"V","param_group":"heater"},{"key":"Ah","display_name":"Heater Current","value":"0.15","numeric_value":"0.15","unit":"A","param_group":"heater"}],"sections":[{"section_number":1,"section_label":"Triode (Oscillator)","tube_type_key":"small_signal_triode","specs":[{"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":"3.2","numeric_value":"3.2","unit":"mA","param_group":"typical_operating"}]},{"section_number":2,"section_label":"Heptode (Mixer)","tube_type_key":"hexode","specs":[{"key":"Va","display_name":"Anode Voltage (typical)","value":"200","numeric_value":"200","unit":"V","param_group":"typical_operating"},{"key":"Vs","display_name":"Screen Voltage (typical)","value":"119","numeric_value":"119","unit":"V","param_group":"typical_operating"},{"key":"Vg","display_name":"Grid 1 Bias Voltage","value":"-2.3","numeric_value":"-2.3","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"3.7","numeric_value":"3.7","unit":"mA","param_group":"typical_operating"},{"key":"mAs","display_name":"Screen Current","value":"8.1","numeric_value":"8.1","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"1000000","numeric_value":"1000000","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"0.775","numeric_value":"0.775","unit":"mA/V","param_group":"typical_operating"}]}],"synced_at":"2026-04-07T12:48:22.600Z"}