{"type_number":"274A","canonical_url":"https://tubeofile.com/tubes/274A","manufacturer":"Western Electric","tube_type_key":"rectifier","tube_type_display_name":"Rectifier","base_name":"UX4","description":"Western Electric full-wave high-vacuum rectifier with directly heated (filament) cathode. Uses a medium four-pin thrust base (UX4). Comprises two filament-type diode units with a common filament, designed to supply DC up to 200 mA from an AC source. Developed by Bell Telephone Laboratories for use in Western Electric amplifiers and telephone carrier equipment. Copyright 1936 Western Electric.","is_directly_heated":true,"completeness":"high","notes":["Directly heated (filament cathode) — observe heater warm-up time before applying B+ to protect the tube and filter capacitors.","Choke-input filter preferred over condenser-input filter for better regulation and longer tube life.","With choke-input filter: max 550 V RMS per plate at 200 mA, or 660 V RMS at 160 mA (maximum operating condition).","With condenser-input filter: max 450 V RMS per plate at 150 mA (maximum with 4 µF capacitor).","Input condenser should preferably not exceed 4 µF with condenser-input filter.","A less severe operating condition should be selected wherever possible — tube life at maximum conditions may be shorter.","Double the listed rectified current may be obtained by connecting the two plates together and using one tube in each side of the circuit.","Socket: Western Electric 143B or equivalent standard four-contact type.","Mounting: vertical or horizontal. If horizontal, filament planes should be vertical.","A development of Bell Telephone Laboratories, American Telephone and Telegraph Company, and Western Electric Company.","Vdrop ≈ 80V derived from WE 274A datasheet Fig. 3 (single-plate I/V curve) at 200 mA per-plate instantaneous current — corresponds to full rated 200 mA DC output with choke-input filter, where each plate conducts the full load current during its half cycle. WE does not publish Vdrop as a discrete value; it must be read off the curve. The 274A's relatively high drop (~80V vs ~58V for 5Z3/5U4) is intentional — WE designed it as a 'soft' rectifier for gradual B+ ramp-up in their amplifiers."],"references":["https://frank.yueksel.org/sheets/136/2/274A.pdf"],"source_urls":{"r_type":null,"tdsl":"http://tdsl.duncanamps.com/show.php?des=274A","radiomuseum":"https://www.radiomuseum.org/tubes/tube_274a.html"},"raw_equivalents":["WE274A","CV2603"],"equivalents":[],"similar":[{"type_number":"274B","reason":"Later WE type with higher current rating — different maximum ratings, not a direct drop-in replacement","has_detail_page":false},{"type_number":"4274A","reason":"STC (Standard Telephones & Cables) equivalent designation for the 274A — same UX4 base and 5V/2A filament but may have slightly different ratings per STC specs","has_detail_page":false},{"type_number":"5Z3","reason":"Same UX4 base and 5V filament, higher current rating (225 mA vs 200 mA) and higher filament current (3.0 A vs 2.0 A) — not a direct substitute","has_detail_page":true},{"type_number":"80","reason":"Same UX4 base but lower current rating (125 mA) and lower max voltage — predecessor generation rectifier","has_detail_page":true},{"type_number":"CV1451","reason":"British CV designation listed as normally replaceable but slightly different per radiomuseum","has_detail_page":false}],"pins":[{"pin_number":"1","function":"Anode 1 (Plate 1)","function_code":"a1","notes":null},{"pin_number":"2","function":"Filament","function_code":"h","notes":null},{"pin_number":"3","function":"Anode 2 (Plate 2)","function_code":"a2","notes":null},{"pin_number":"4","function":"Filament","function_code":"h","notes":null}],"specs":[{"key":"Vh","display_name":"Heater Voltage","value":"5.0","numeric_value":"5","unit":"V","param_group":"heater"},{"key":"Ah","display_name":"Heater Current","value":"2.0","numeric_value":"2","unit":"A","param_group":"heater"}],"sections":[{"section_number":1,"section_label":"Rectifier","tube_type_key":"rectifier","specs":[{"key":"Va_max","display_name":"Anode Voltage (max)","value":"550","numeric_value":"550","unit":"V","param_group":"absolute_max"},{"key":"PIV","display_name":"Peak Inverse Voltage","value":"1500","numeric_value":"1500","unit":"V","param_group":"rectifier"},{"key":"Vdrop","display_name":"Voltage Drop (typical)","value":"80","numeric_value":"80","unit":"V","param_group":"rectifier"},{"key":"C_max","display_name":"Max C-input Filter Capacitor","value":"4","numeric_value":"4","unit":"µF","param_group":"rectifier"},{"key":"Ia_peak","display_name":"Peak Anode Current (surge)","value":"500","numeric_value":"500","unit":"mA","param_group":"rectifier"},{"key":"Idc_max","display_name":"Max DC Output Current (total, not per-anode)","value":"200","numeric_value":"200","unit":"mA","param_group":"rectifier"}]}],"synced_at":"2026-04-08T12:18:13.627Z"}