{"type_number":"7Z4","canonical_url":"https://tubeofile.com/tubes/7Z4","manufacturer":"RCA","tube_type_key":"rectifier","tube_type_display_name":"Rectifier","base_name":"Loctal","description":"Heater-type high-vacuum full-wave rectifier in Loctal (Lock-In) 8-pin construction. Designed for power-supply service in AC-operated receivers and industrial equipment using the 7 V / 6.3 V loctal series. Higher-current sibling of the 7Y4.","is_directly_heated":false,"completeness":"high","notes":["JEDEC base 5AB — Loctal 8-pin lock-in base, same pinout as 7Y4.","Nominal heater 7.0 V / 0.96 A; datasheet-rated at 6.3 V / 0.9 A for the 6.3 V bus. Both are supported.","Unipotential cathode with ±450 V peak heater-to-cathode rating — higher than many 6 V rectifiers and permits stacked-heater designs.","Max AC plate-to-plate supply voltage: 650 V RMS (cap input) or 900 V RMS (choke input) — i.e. 325 V / 450 V per plate. Verify filter topology before applying the higher rating.","DC output voltage regulation from half load to full load is approximately 35 V (cap input) or 15 V (choke input) per the RCA 1947 datasheet.","Tung-Sol 1948 datasheet explicitly states tube voltage drop of 40 V measured with the tube conducting 100 mA each plate — this is the definitive Vdrop figure.","Filter-input capacitor larger than 40 µF may require additional plate-supply impedance above the 75 Ω min per plate to avoid exceeding the 300 mA peak plate current rating.","US military designation VT-181 per MIL-HDBK-213A; British CV number CV1790."],"references":["https://frank.pocnet.net/sheets/127/7/7Z4.pdf","https://frank.pocnet.net/sheets/049/7/7Z4.pdf"],"source_urls":{"r_type":null,"tdsl":"https://tdsl.duncanamps.com/show.php?des=7Z4","radiomuseum":"https://www.radiomuseum.org/tubes/tube_7z4.html"},"raw_equivalents":["CV1790","VT-181"],"equivalents":[],"similar":[{"type_number":"6BW4","reason":"Same electricals (6.3 V / 0.9 A / 100 mA / 40 V drop) but Noval base (9DJ) — not pin-compatible with Loctal","has_detail_page":true},{"type_number":"7Y4","reason":"Same Loctal base and same pinout but lower ratings (70 mA DC out, 22 V drop, 0.5 A heater) — 7Z4 can substitute for 7Y4 but not vice versa at full load","has_detail_page":true}],"pins":[{"pin_number":"1","function":"Heater","function_code":"h","notes":null},{"pin_number":"2","function":"No Connection","function_code":"nc","notes":null},{"pin_number":"3","function":"Plate 2 (Anode 2)","function_code":"a2","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":"Plate 1 (Anode 1)","function_code":"a1","notes":null},{"pin_number":"7","function":"Cathode","function_code":"k","notes":null},{"pin_number":"8","function":"Heater","function_code":"h","notes":null}],"specs":[{"key":"Vh","display_name":"Heater Voltage","value":"6.3","numeric_value":"6.3","unit":"V","param_group":"heater"},{"key":"Ah","display_name":"Heater Current","value":"0.9","numeric_value":"0.9","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":"40","numeric_value":"40","unit":"V","param_group":"rectifier"},{"key":"Ia_peak","display_name":"Peak Anode Current (surge)","value":"300","numeric_value":"300","unit":"mA","param_group":"rectifier"},{"key":"Idc_max","display_name":"Max DC Output Current (total, not per-anode)","value":"100","numeric_value":"100","unit":"mA","param_group":"rectifier"},{"key":"Rs_min","display_name":"Min Series Resistance (C-input)","value":"75","numeric_value":"75","unit":"Ω","param_group":"rectifier"}]}],"synced_at":"2026-04-09T05:17:45.889Z"}