{"type_number":"IW4/350","canonical_url":"https://tubeofile.com/tubes/IW4%2F350","manufacturer":"Mullard","tube_type_key":"rectifier","tube_type_display_name":"Rectifier","base_name":"B4","description":"Full-wave vacuum rectifier with indirectly heated (half-indirect) cathode and 4-pin European base, manufactured by Mullard. Designed for power supply rectification in AC radio receivers. Maximum voltage rating 350V per anode. Used in British radio equipment from the mid-1930s to mid-1940s.","is_directly_heated":false,"completeness":"medium","notes":["Half-indirect heating — a transitional cathode design between direct and fully indirect heating.","European B4 (4-pin) base with 4V/2A filament.","Valve Equivalents reference lists as 'Double Diode' with B4 base and 4V heater.","Used in 66 documented radio models (1936-1946) per Radiomuseum.","Also referred to as 1W4/350 in some references (Taschenbuch 1948/49).","Peak Inverse Voltage is not explicitly stated in the Mazda IW4-350 datasheet; PIV=990 V is derived from the standard full-wave capacitor-input relation PIV = 2 × √2 × Va_max (350 Vrms). Matches the convention used for AZ12, UU4, UU5, EZ41 in this repo."],"references":["https://tdsl.duncanamps.com/show.php?des=IW4/350","https://www.radiomuseum.org/tubes/?tube=IW4/350"],"source_urls":{"r_type":null,"tdsl":"https://tdsl.duncanamps.com/show.php?des=IW4/350","radiomuseum":"https://www.radiomuseum.org/tubes/tube_iw4_350.html"},"raw_equivalents":[],"equivalents":[],"similar":[{"type_number":"A11D","reason":"Radiomuseum lists as similar rectifier alternative","has_detail_page":false},{"type_number":"IW4","reason":"Same family but lower voltage rating — not interchangeable if circuit requires 350V rating","has_detail_page":false},{"type_number":"R2","reason":"Radiomuseum lists as similar rectifier alternative","has_detail_page":false}],"pins":[{"pin_number":"1","function":"Anode 1","function_code":"a1","notes":null},{"pin_number":"2","function":"Heater/Cathode","function_code":"h","notes":null},{"pin_number":"3","function":"Anode 2","function_code":"a2","notes":null},{"pin_number":"4","function":"Heater/Cathode","function_code":"h","notes":null}],"specs":[{"key":"Vh","display_name":"Heater Voltage","value":"4","numeric_value":"4","unit":"V","param_group":"heater"},{"key":"Ah","display_name":"Heater Current","value":"2","numeric_value":"2","unit":"A","param_group":"heater"}],"sections":[{"section_number":1,"section_label":"Full-Wave Rectifier","tube_type_key":"rectifier","specs":[{"key":"Va_max","display_name":"Anode Voltage (max)","value":"350","numeric_value":"350","unit":"V","param_group":"absolute_max"},{"key":"PIV","display_name":"Peak Inverse Voltage","value":"990","numeric_value":"990","unit":"V","param_group":"rectifier"},{"key":"Idc_max","display_name":"Max DC Output Current (total, not per-anode)","value":"120","numeric_value":"120","unit":"mA","param_group":"rectifier"}]}],"synced_at":"2026-04-08T07:56:27.592Z"}