{"type_number":"UU5","canonical_url":"https://tubeofile.com/tubes/UU5","manufacturer":"Mazda","tube_type_key":"rectifier","tube_type_display_name":"Rectifier","base_name":"B4","description":"Full-wave vacuum rectifier with indirectly heated cathode, designed for AC mains power supply applications. Introduced by Mazda (Ediswan) in 1936 for use in radio receivers and audio equipment. Rated for 500V RMS per anode at 120 mA DC output with 8 µF capacitor-input filter.","is_directly_heated":false,"completeness":"high","notes":["Indirectly heated cathode — one side of the heater is internally connected to the cathode at pin 3. This provides controlled warm-up, preventing high-voltage surges on filter capacitors that occur with directly-heated rectifiers.","Base type is B4 (European 4-pin, also designated 'Eu A' or 'E'). Not to be confused with the American UX4 base which has different pin spacing.","Maximum reservoir (C-input filter) capacitor is 8 µF. The Osram MU14 datasheet specifies operation with 4 µF input capacitor — verify capacitor compatibility when substituting.","Designed to replace the earlier UU120/500. Manufactured by British Thomson-Houston Co. Ltd. under the Mazda brand.","The Mazda UU5 was one of the first British indirectly heated rectifiers alongside the GEC/Osram MU14 (1933) and Mazda UU4 (1935). The indirectly heated cathode allowed tighter cathode-to-plate spacing than directly-heated types, reducing voltage drop.","Vdrop ≈ 40V estimated from Mazda UU5 datasheet (Vtr=2×500V, Io=120mA → Vo=580V; higher peak voltage class than UU4 so slightly higher drop per pure tube physics). Source: Mazda UU4/UU5 datasheet."],"references":["https://frank.pocnet.net/sheets/146/u/UU4.pdf","https://frank.pocnet.net/sheets/060/m/MU12.pdf"],"source_urls":{"r_type":"http://www.r-type.org/exhib/aaa0457.htm","tdsl":"https://tdsl.duncanamps.com/show.php?des=UU5","radiomuseum":"https://www.radiomuseum.org/tubes/tube_uu5.html"},"raw_equivalents":["MU14","APV4","CV1039","CV3760"],"equivalents":[],"similar":[{"type_number":"6BT4","reason":"American substitute per Sams handbook — different base and 6.3V heater, requires rewiring","has_detail_page":false},{"type_number":"MU12","reason":"Same B4 base and pinout but lower voltage rating (350V max vs 500V) — not safe as drop-in in 500V circuits","has_detail_page":true},{"type_number":"UU4","reason":"Mazda's 350V version — same base and pinout but lower voltage rating (350V max)","has_detail_page":true}],"pins":[{"pin_number":"1","function":"Anode 1","function_code":"a1","notes":null},{"pin_number":"2","function":"Anode 2","function_code":"a2","notes":null},{"pin_number":"3","function":"Heater and Cathode","function_code":"k","notes":null},{"pin_number":"4","function":"Heater","function_code":"h","notes":null}],"specs":[{"key":"Vh","display_name":"Heater Voltage","value":"4.0","numeric_value":"4","unit":"V","param_group":"heater"},{"key":"Ah","display_name":"Heater Current","value":"2.3","numeric_value":"2.3","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":"500","numeric_value":"500","unit":"V","param_group":"absolute_max"},{"key":"PIV","display_name":"Peak Inverse Voltage","value":"1414","numeric_value":"1414","unit":"V","param_group":"rectifier"},{"key":"Vdrop","display_name":"Voltage Drop (typical)","value":"40","numeric_value":"40","unit":"V","param_group":"rectifier"},{"key":"C_max","display_name":"Max C-input Filter Capacitor","value":"8","numeric_value":"8","unit":"µF","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":"2026-04-09T05:19:00.933Z"}