{"type_number":"836","canonical_url":"https://tubeofile.com/tubes/836","manufacturer":null,"tube_type_key":"rectifier","tube_type_display_name":"Rectifier","base_name":"UX4","description":"Half-wave mercury-vapor rectifier for high-voltage power supply applications. Uses a directly heated cathode with mercury-vapor fill providing low, constant voltage drop. Designed for transmitter and industrial rectifier circuits requiring moderate current at high voltage.","is_directly_heated":true,"completeness":"medium","notes":["Mercury-vapor tube — must be operated within the specified condensed-mercury temperature range. Outside this range, tube life and performance degrade significantly.","Filament must be applied before anode voltage to allow mercury vapor pressure to stabilize.","Uses Jumbo 4-pin bayonet base (1918 pattern) — physically larger than the standard UX4 base. Not interchangeable with UX4-based tubes.","Radiomuseum classifies this as 'Half-Wave Vacuum Rectifier' but other sources indicate mercury-vapor fill. The 2.5 V / 5 A filament and high PIV rating are consistent with mercury-vapor transmitting rectifier practice.","Higher current capacity than the 816 (250 mA avg vs 125 mA) but lower PIV (5000 V vs 7500 V).","Peak anode current rating of 1000 mA allows use in capacitor-input filter circuits with appropriate series resistance."],"references":["https://tdsl.duncanamps.com/show.php?des=836","https://www.radiomuseum.org/tubes/?tube=836"],"source_urls":{"r_type":null,"tdsl":"https://tdsl.duncanamps.com/show.php?des=836","radiomuseum":"https://www.radiomuseum.org/tubes/tube_836.html"},"raw_equivalents":["CV636","VT236"],"equivalents":[],"similar":[{"type_number":"816","reason":"Smaller half-wave mercury-vapor rectifier (125 mA avg, 7500 V PIV); UX4 base — not pin-compatible","has_detail_page":true},{"type_number":"872A","reason":"Larger half-wave mercury-vapor rectifier (1250 mA avg, 10000 V PIV); same Jumbo 4-pin bayonet base family","has_detail_page":true}],"pins":[{"pin_number":"1","function":"Filament","function_code":"h","notes":null},{"pin_number":"2","function":"Anode","function_code":"a","notes":null},{"pin_number":"3","function":"No Connection","function_code":"nc","notes":null},{"pin_number":"4","function":"Filament","function_code":"h","notes":null}],"specs":[{"key":"Vh","display_name":"Heater Voltage","value":"2.5","numeric_value":"2.5","unit":"V","param_group":"heater"},{"key":"Ah","display_name":"Heater Current","value":"5","numeric_value":"5","unit":"A","param_group":"heater"}],"sections":[{"section_number":1,"section_label":"Rectifier","tube_type_key":"rectifier","specs":[{"key":"PIV","display_name":"Peak Inverse Voltage","value":"5000","numeric_value":"5000","unit":"V","param_group":"rectifier"},{"key":"Ia_peak","display_name":"Peak Anode Current (surge)","value":"1000","numeric_value":"1000","unit":"mA","param_group":"rectifier"},{"key":"Idc_max","display_name":"Max DC Output Current (total, not per-anode)","value":"250","numeric_value":"250","unit":"mA","param_group":"rectifier"}]}],"synced_at":"2026-04-08T07:53:57.593Z"}