{"type_number":"76","canonical_url":"https://tubeofile.com/tubes/76","manufacturer":"RCA","tube_type_key":"small_signal_triode","tube_type_display_name":"Small Signal Triode","base_name":"UX5","description":"Medium-mu triode for use as detector, amplifier, or oscillator. Indirectly heated, heater-cathode type with characteristics identical to the type 56 except for 6.3V heater. Especially useful in resistance-coupled audio-frequency amplifiers.","is_directly_heated":false,"completeness":"high","notes":["Electrically identical to the type 56, differing only in heater voltage (6.3V vs 2.5V) and heater current (0.3A vs 1.0A). Introduced in March 1933 as the 6.3V heater replacement for the 56.","Succeeded by the 6P5GT, 6C5G, 6P5G, and 6P5M on Octal bases. The 76 uses the pre-war UX5 (Small-Shell Small 5-Pin) base with basing designation 5A.","The Sams Tube Substitution Handbook lists the 37, 37A, 56A*, 56AS*, 67*, and 67A* as substitutes for the 76 (* = may not work in all circuits). The 37/37A share the same base and heater but have different electrical characteristics (lower mu).","Maximum grid-circuit resistance is 1.0 megohm. The cathode should preferably be connected to a mid-tap on the heater supply winding or to a center-tapped resistor across the heater winding. Heater-to-cathode voltage must not exceed 90V.","One of the classic pre-war American triodes, documented in over 2,000 radio receiver models from 1933 to 1953. Widely used in AC-powered superheterodyne receivers of the 1930s as detector and first audio stage."],"references":["https://frank.pocnet.net/sheets/021/7/76.pdf","https://frank.pocnet.net/sheets/127/7/76.pdf"],"source_urls":{"r_type":"https://www.r-type.org/exhib/aac0025.htm","tdsl":"https://tdsl.duncanamps.com/show.php?des=76","radiomuseum":"https://www.radiomuseum.org/tubes/tube_76.html"},"raw_equivalents":["CV615","VT-76","37","6P5GT"],"equivalents":[{"type_number":"37","equivalence_type":"direct","notes":null},{"type_number":"6P5GT","equivalence_type":"direct","notes":null}],"similar":[{"type_number":"56","reason":"Electrically identical but 2.5V/1.0A heater on UX5 base — 76 uses 6.3V/0.3A","has_detail_page":true},{"type_number":"6C5","reason":"Similar medium-mu triode successor on Octal base — not pin-compatible with UX5","has_detail_page":true},{"type_number":"6P5G","reason":"Electrically identical but Octal base — not pin-compatible with UX5","has_detail_page":false}],"pins":[{"pin_number":"1","function":"Heater","function_code":"h","notes":null},{"pin_number":"2","function":"Anode (Plate)","function_code":"a","notes":null},{"pin_number":"3","function":"Control Grid","function_code":"g1","notes":null},{"pin_number":"4","function":"Cathode","function_code":"k","notes":null},{"pin_number":"5","function":"Heater","function_code":"h","notes":null}],"specs":[{"key":"Vh","display_name":"Heater Voltage","value":"6.3","numeric_value":"6.3","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":"Triode","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":"1.4","numeric_value":"1.4","unit":"W","param_group":"absolute_max"},{"key":"Vhk_max","display_name":"Heater-to-Cathode Voltage (max)","value":"90","numeric_value":"90","unit":"V","param_group":"absolute_max"},{"key":"Rg_max","display_name":"Max Grid Resistor","value":"1.0","numeric_value":"1","unit":"MΩ","param_group":"absolute_max"},{"key":"Va","display_name":"Anode Voltage (typical)","value":"250","numeric_value":"250","unit":"V","param_group":"typical_operating"},{"key":"Vg","display_name":"Grid 1 Bias Voltage","value":"-13.5","numeric_value":"-13.5","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"5","numeric_value":"5","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"9500","numeric_value":"9500","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"1.45","numeric_value":"1.45","unit":"mA/V","param_group":"typical_operating"},{"key":"mu","display_name":"Amplification Factor (μ)","value":"13.8","numeric_value":"13.8","unit":"—","param_group":"typical_operating"},{"key":"Cgp","display_name":"Grid-to-Plate Capacitance","value":"2.8","numeric_value":"2.8","unit":"pF","param_group":"capacitances"},{"key":"Cgk","display_name":"Grid-to-Cathode Capacitance","value":"3.5","numeric_value":"3.5","unit":"pF","param_group":"capacitances"},{"key":"Cak","display_name":"Anode-to-Cathode Capacitance","value":"2.5","numeric_value":"2.5","unit":"pF","param_group":"capacitances"}]}],"synced_at":"2026-04-07T19:05:21.617Z"}