{"type_number":"8005","canonical_url":"https://tubeofile.com/tubes/8005","manufacturer":"RCA","tube_type_key":"power_triode","tube_type_display_name":"Power Triode","base_name":"UX4","description":"Directly-heated thoriated-tungsten filament medium-mu power triode designed for AF power amplifier, modulator, RF power amplifier, and oscillator service. Rated 75 W plate dissipation (85 W ICAS) with 1250 V (CCS) / 1500 V (ICAS) maximum plate voltage. Introduced by RCA and used in military and commercial transmitters, notably the McIntosh MI-200 amplifier. Glass envelope (ST-19) with top-cap anode and medium-metal-shell small 4-pin bayonet base.","is_directly_heated":true,"completeness":"high","notes":["Directly-heated thoriated-tungsten filament: the filament serves as the cathode; there is no heater-cathode isolation.","Top-cap anode: the plate connection is via a medium metal cap on top of the ST-19 envelope, not via a base pin. Pin 2 is No Connection.","Base is a medium-metal-shell small 4-pin bayonet (basing designation 3G).","gm and ra are not stated in the RCA datasheet; the values recorded here were derived from the published Average Plate Characteristics curves (RCA drawing 92C-6279, April 30 1941) near an operating point of Va = 1500 V, Vg = -100 V and are approximate. mu = 20 is the datasheet nominal (range 18-22).","Class B AF modulator (two tubes, ICAS): Va = 1500 V, Vg = -67.5 V, Ia(zero-signal) = 40 mA, Ia(max-signal) = 330 mA, plate-to-plate load 9800 Ω, Pout ≈ 330 W.","Class C RF telegraphy (ICAS): Va = 1500 V, Vg = -130 V, Ia = 200 mA, Pout ≈ 220 W per tube.","Grid-leak bias is the preferred bias method due to automatic bias adjustment under fluctuating load; if fixed bias is used at 1500 V plate, RCA recommends approximately -50 V fixed bias plus grid-leak.","Filament voltage tolerance is ±0.5 V (9.5-10.5 V).","Historically used in the McIntosh MI-200 200-watt audio amplifier (WWII / early post-war) where pairs of 8005s were run in Class AB/B push-pull."],"references":["https://frank.pocnet.net/sheets/049/8/8005.pdf","https://www.radiomuseum.org/tubes/tube_8005.html"],"source_urls":{"r_type":null,"tdsl":"https://tdsl.duncanamps.com/show.php?des=8005","radiomuseum":"https://www.radiomuseum.org/tubes/tube_8005.html"},"raw_equivalents":["OT100","V70D","T60"],"equivalents":[],"similar":[{"type_number":"211","reason":"Higher-voltage power triode (mu 12, Pa_max 100 W, filament 10 V/3.25 A, top-cap anode); different electricals (lower mu) and higher dissipation — not a drop-in substitute","has_detail_page":true},{"type_number":"75TH","reason":"Medium-mu Eimac transmitting triode with similar Pa_max (75 W) and mu (~20), but 5 V/6.25 A filament and no top-cap anode — not pin-compatible","has_detail_page":true},{"type_number":"805","reason":"Higher-power RCA transmitting triode (Pa_max 125 W, mu ~45, 10 V/3.25 A filament) — different mu class and higher ratings, not a drop-in substitute","has_detail_page":false}],"pins":[{"pin_number":"1","function":"Filament","function_code":"h","notes":null},{"pin_number":"2","function":"No Connection","function_code":"nc","notes":null},{"pin_number":"3","function":"Control Grid","function_code":"g1","notes":null},{"pin_number":"4","function":"Filament","function_code":"h","notes":null},{"pin_number":"TC","function":"Plate (Anode)","function_code":"a","notes":null}],"specs":[{"key":"Vh","display_name":"Heater Voltage","value":"10","numeric_value":"10","unit":"V","param_group":"heater"},{"key":"Ah","display_name":"Heater Current","value":"3.25","numeric_value":"3.25","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":"1500","numeric_value":"1500","unit":"V","param_group":"absolute_max"},{"key":"Pa_max","display_name":"Anode Dissipation (max)","value":"85","numeric_value":"85","unit":"W","param_group":"absolute_max"},{"key":"Ik_max","display_name":"Cathode Current (max)","value":"330","numeric_value":"330","unit":"mA","param_group":"absolute_max"},{"key":"Va","display_name":"Anode Voltage (typical)","value":"1500","numeric_value":"1500","unit":"V","param_group":"typical_operating"},{"key":"Vg","display_name":"Grid 1 Bias Voltage","value":"-67.5","numeric_value":"-67.5","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"40","numeric_value":"40","unit":"mA","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":"5.7","numeric_value":"5.7","unit":"mA/V","param_group":"typical_operating"},{"key":"mu","display_name":"Amplification Factor (μ)","value":"20","numeric_value":"20","unit":"—","param_group":"typical_operating"},{"key":"Pout","display_name":"Output Power","value":"330","numeric_value":"330","unit":"W","param_group":"output"},{"key":"Cgp","display_name":"Grid-to-Plate Capacitance","value":"5","numeric_value":"5","unit":"pF","param_group":"capacitances"},{"key":"Cin","display_name":"Input Capacitance","value":"6.4","numeric_value":"6.4","unit":"pF","param_group":"capacitances"},{"key":"Cout","display_name":"Output Capacitance","value":"1","numeric_value":"1","unit":"pF","param_group":"capacitances"}]}],"synced_at":"2026-04-09T05:17:50.354Z"}