{"type_number":"12X4","canonical_url":"https://tubeofile.com/tubes/12X4","manufacturer":null,"tube_type_key":"rectifier","tube_type_display_name":"Rectifier","base_name":"B7G","description":"Miniature heater-cathode type twin diode designed for full-wave rectifier operation in compact power supplies. 12.6V heater version of the 6X4, developed for vibrator power supplies in car radios and series-string heater circuits.","is_directly_heated":false,"completeness":"high","notes":["12.6V heater version of the 6X4. Heater current is 0.3A at 12.6V (vs 0.6A at 6.3V for the 6X4). Same heater power, different voltage/current ratio.","Developed primarily for vibrator power supplies in automobile radios where a 12.6V heater supply is available from the vehicle battery.","GE Essential Characteristics confirms 12.6V/0.3A heater, B7G (5BS) basing, full-wave rectifier service.","Rectifier reference gives Vdrop=22V at rated DC output, max DC output 90 mA, max AC voltage 360V RMS.","Maximum ratings with capacitor-input filter: AC plate-supply voltage per plate 325V RMS at 70 mA. With choke-input: 450V RMS at 70 mA.","Brans Vademecum groups the 12X4 with the 6X4/EZ90 family across multiple base types."],"references":["https://frank.pocnet.net/sheets/049/6/6X4.pdf"],"source_urls":{"r_type":null,"tdsl":"https://tdsl.duncanamps.com/show.php?des=12X4","radiomuseum":"https://www.radiomuseum.org/tubes/tube_12x4.html"},"raw_equivalents":[],"equivalents":[],"similar":[{"type_number":"6X4","reason":"Electrically identical but 6.3V/0.6A heater — not a drop-in in 12.6V heater circuits","has_detail_page":true},{"type_number":"EZ90","reason":"European designation for the 6X4 (6.3V heater) — not a drop-in in 12.6V circuits","has_detail_page":false}],"pins":[{"pin_number":"1","function":"Plate 2 (Anode 2)","function_code":"a2","notes":null},{"pin_number":"2","function":"No Connection","function_code":"nc","notes":null},{"pin_number":"3","function":"Heater","function_code":"h","notes":null},{"pin_number":"4","function":"Heater","function_code":"h","notes":null},{"pin_number":"5","function":"No Connection","function_code":"nc","notes":null},{"pin_number":"6","function":"Plate 1 (Anode 1)","function_code":"a1","notes":null},{"pin_number":"7","function":"Cathode","function_code":"k","notes":null}],"specs":[{"key":"Vh","display_name":"Heater Voltage","value":"12.6","numeric_value":"12.6","unit":"V","param_group":"heater"},{"key":"Ah","display_name":"Heater Current","value":"0.3","numeric_value":"0.3","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":"450","numeric_value":"450","unit":"V","param_group":"absolute_max"},{"key":"Vhk_max","display_name":"Heater-to-Cathode Voltage (max)","value":"450","numeric_value":"450","unit":"V","param_group":"absolute_max"},{"key":"PIV","display_name":"Peak Inverse Voltage","value":"1250","numeric_value":"1250","unit":"V","param_group":"rectifier"},{"key":"Vdrop","display_name":"Voltage Drop (typical)","value":"22","numeric_value":"22","unit":"V","param_group":"rectifier"},{"key":"C_max","display_name":"Max C-input Filter Capacitor","value":"40","numeric_value":"40","unit":"µF","param_group":"rectifier"},{"key":"Ia_peak","display_name":"Peak Anode Current (surge)","value":"245","numeric_value":"245","unit":"mA","param_group":"rectifier"},{"key":"Idc_max","display_name":"Max DC Output Current (total, not per-anode)","value":"70","numeric_value":"70","unit":"mA","param_group":"rectifier"},{"key":"Rs_min","display_name":"Min Series Resistance (C-input)","value":"525","numeric_value":"525","unit":"Ω","param_group":"rectifier"}]}],"synced_at":"2026-04-08T07:49:18.483Z"}