{"type_number":"12D4","canonical_url":"https://tubeofile.com/tubes/12D4","manufacturer":"RCA","tube_type_key":"rectifier","tube_type_display_name":"Rectifier","base_name":"Octal","description":"Half-wave high-vacuum rectifier with indirectly-heated unipotential cathode, intended for TV damper service in equipment having series heater-string arrangement. Noval (9-pin miniature) base with intermediate-shell Octal 5-pin or 6-pin mounting options. RCA tentative data, dated April 1959.","is_directly_heated":false,"completeness":"high","notes":["Tentative data — the 12D4 was introduced by RCA in 1959 for TV damper service.","The 12D4A is a different-rating variant (per TDSL); verify suitability before substitution.","Pin 2 is an internal connection — do not use as a tie point.","Socket terminals 1, 3, and 6 should not be used as tie points.","Base designation 4CG (per GE Essential Characteristics and RCA datasheet).","Heater negative with respect to cathode: 4400V max. Heater positive with respect to cathode: 300V max.","Peak inverse plate voltage rating of 4400V applies when duty cycle of voltage pulse does not exceed 15% of one horizontal scanning cycle (525-line, 30-frame system).","DC component of plate voltage must not exceed 900V. DC component of heater-cathode voltage must not exceed 100V.","Tube voltage drop (Vdrop) is not stated as a discrete figure in the RCA datasheet. Derived from the Average Plate Characteristic curve (92CS-9757, Ef=12.6V) at the maximum DC plate current of 155 mA, where plate voltage reads approximately 18 V."],"references":["https://frank.pocnet.net/sheets/049/1/12D4.pdf"],"source_urls":{"r_type":null,"tdsl":"https://tdsl.duncanamps.com/show.php?des=12D4","radiomuseum":"https://www.radiomuseum.org/tubes/tube_12d4.html"},"raw_equivalents":["12D4A"],"equivalents":[],"similar":[{"type_number":"17D4","reason":"Same half-wave TV damper rectifier family but 16.8V heater — not pin-compatible without heater string redesign","has_detail_page":false},{"type_number":"25D4","reason":"Same half-wave TV damper rectifier family but 25V heater — not pin-compatible without heater string redesign","has_detail_page":false},{"type_number":"6AX4GTB","reason":"Half-wave TV damper rectifier but 6.3V heater, Octal base — different base and heater voltage","has_detail_page":false},{"type_number":"6DA4","reason":"Identical electrically but 6.3V heater — not a drop-in replacement in TV series heater string circuits","has_detail_page":true}],"pins":[{"pin_number":"1","function":"Same as Pin 10 (Shell)","function_code":"ia","notes":null},{"pin_number":"2","function":"Internal Connection","function_code":"ic","notes":null},{"pin_number":"3","function":"Cathode","function_code":"k","notes":null},{"pin_number":"4","function":"No Connection","function_code":"nc","notes":null},{"pin_number":"5","function":"Plate","function_code":"a","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":"Heater","function_code":"h","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","tube_type_key":"rectifier","specs":[{"key":"Pa_max","display_name":"Anode Dissipation (max)","value":"5.5","numeric_value":"5.5","unit":"W","param_group":"absolute_max"},{"key":"Vhk_max","display_name":"Heater-to-Cathode Voltage (max)","value":"4400","numeric_value":"4400","unit":"V","param_group":"absolute_max"},{"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":"18","numeric_value":"18","unit":"V","param_group":"rectifier"},{"key":"Idc_max","display_name":"Max DC Output Current (total, not per-anode)","value":"155","numeric_value":"155","unit":"mA","param_group":"rectifier"},{"key":"Ia_peak","display_name":"Peak Anode Current (surge)","value":"900","numeric_value":"900","unit":"mA","param_group":"rectifier"}]}],"synced_at":"2026-04-09T05:16:19.486Z"}