{"type_number":"12AX4","canonical_url":"https://tubeofile.com/tubes/12AX4","manufacturer":null,"tube_type_key":"rectifier","tube_type_display_name":"Rectifier","base_name":"Octal","description":"Half-wave vacuum rectifier (damper diode) with indirectly heated cathode, designed for use as a boost rectifier in horizontal deflection circuits of television receivers. Octal base with 12.6V/0.6A heater. High PIV rating (4400V) for flyback pulse handling.","is_directly_heated":false,"completeness":"high","notes":["TDSL lists 12AX4GT as a different-rating variant, and 6AX4GTA as the 6.3V heater version.","The GTA and GTB suffixes indicate improved glass envelope designs with the same electrical ratings.","Half-wave damper diode — used to recover energy stored in the horizontal deflection yoke inductance and boost the B+ supply voltage.","Peak inverse voltage of 4400V handles the flyback pulse generated during horizontal retrace.","Peak output current of 750 mA; DC output current rating is 125 mA in boost rectifier service.","Heater-cathode voltage rating is critical in this application — cathode operates at high positive potential relative to chassis ground.","Tube voltage drop (Vdrop) of 32V at Ib=250 mA DC is explicitly stated under 'Typical Operating Conditions and Characteristics' in the Tung-Sol 12AX4GTB datasheet (December 1, 1960, Plate #6052)."],"references":["https://tdsl.duncanamps.com/show.php?des=12AX4","https://www.radiomuseum.org/tubes/?tube=12AX4","https://frank.pocnet.net/sheets/127/1/12AX4GTB.pdf"],"source_urls":{"r_type":null,"tdsl":"https://tdsl.duncanamps.com/show.php?des=12AX4GTA","radiomuseum":"https://www.radiomuseum.org/tubes/tube_12ax4gta.html"},"raw_equivalents":["12AX4GT","12AX4GTA","12AX4GTB"],"equivalents":[],"similar":[{"type_number":"6AX4GTA","reason":"Identical damper diode except 6.3V heater instead of 12.6V — same PIV and current ratings","has_detail_page":false},{"type_number":"6BW4","reason":"Full-wave rectifier on Noval base with 6.3V heater — similar TV rectifier service but different base and full-wave vs half-wave topology","has_detail_page":true}],"pins":[{"pin_number":"1","function":"No Connection","function_code":"nc","notes":null},{"pin_number":"2","function":"Heater","function_code":"h","notes":null},{"pin_number":"3","function":"Plate","function_code":"a","notes":null},{"pin_number":"4","function":"No Connection","function_code":"nc","notes":null},{"pin_number":"5","function":"No Connection","function_code":"nc","notes":null},{"pin_number":"6","function":"No Connection","function_code":"nc","notes":null},{"pin_number":"7","function":"Heater","function_code":"h","notes":null},{"pin_number":"8","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":"0.6","numeric_value":"0.6","unit":"A","param_group":"heater"}],"sections":[{"section_number":1,"section_label":"Rectifier (Damper)","tube_type_key":"rectifier","specs":[{"key":"PIV","display_name":"Peak Inverse Voltage","value":"4400","numeric_value":"4400","unit":"V","param_group":"rectifier"},{"key":"Vdrop","display_name":"Voltage Drop (typical)","value":"32","numeric_value":"32","unit":"V","param_group":"rectifier"},{"key":"Ia_peak","display_name":"Peak Anode Current (surge)","value":"750","numeric_value":"750","unit":"mA","param_group":"rectifier"},{"key":"Idc_max","display_name":"Max DC Output Current (total, not per-anode)","value":"125","numeric_value":"125","unit":"mA","param_group":"rectifier"}]}],"synced_at":"2026-04-09T05:16:15.426Z"}