{"type_number":"7Y4","canonical_url":"https://tubeofile.com/tubes/7Y4","manufacturer":"Tung-Sol","tube_type_key":"rectifier","tube_type_display_name":"Rectifier","base_name":"Loctal","description":"Heater-type high-vacuum twin diode in Loctal (Lock-In) 8-pin construction, intended as a full-wave rectifier in compact AC or storage-battery-operated equipment where economy of heater power is desired. Electrically equivalent to the 6X5GT/84 on a Loctal base.","is_directly_heated":false,"completeness":"high","notes":["JEDEC base 5AB — Loctal 8-pin lock-in base. The '7x' prefix in American tube numbering is the convention for Loctal-based tubes on a 6.3 V heater (nominal 7.0 V, operated at 6.3 V).","Unipotential (indirectly heated) cathode with Vhk_max = 450 V, so the heater can share a common 6.3 V winding with signal tubes.","Maximum DC output current is only 70 mA — comparable to a 6X5/84 and significantly lower than 5 V rectifiers like 5Y3/5U4. Verify total B+ draw before substituting.","Maximum AC plate voltage depends on filter topology: 325 V rms per plate with capacitor-input filter, 450 V rms per plate with choke-input filter.","Tung-Sol 1948 datasheet explicitly states tube voltage drop of 22 V measured with tube conducting 70 mA each plate — this is the definitive Vdrop figure.","Capacitor-input operation: if the filter capacitor exceeds 40 µF it may be necessary to increase the plate-supply impedance above the 150 Ω minimum per plate to keep peak plate current within the 210 mA rating.","Sylvania describes 7Y4 as 'GT equivalent 6X5GT' — similar electrical characteristics, smaller envelope, more rugged Lock-In construction."],"references":["https://frank.pocnet.net/sheets/127/7/7Y4.pdf","https://frank.pocnet.net/sheets/084/7/7Y4.pdf"],"source_urls":{"r_type":null,"tdsl":"https://tdsl.duncanamps.com/show.php?des=7Y4","radiomuseum":"https://www.radiomuseum.org/tubes/tube_7y4.html"},"raw_equivalents":["CV901","U149"],"equivalents":[],"similar":[{"type_number":"6X5","reason":"Electrically very similar (6.3 V / 70 mA / 22 V drop / 325 V per plate) but 6X5 uses the Octal base, not Loctal — not pin-compatible","has_detail_page":true},{"type_number":"7Z4","reason":"Same Loctal base and same pinout but higher rating (100 mA, 40 V drop, 0.9 A heater) — different thermal profile, not an electrically identical drop-in","has_detail_page":true},{"type_number":"84","reason":"Same rectifier function and ratings but UX5 (5-pin) base — not pin-compatible with Loctal","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":"0.5","numeric_value":"0.5","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":"Ia_peak","display_name":"Peak Anode Current (surge)","value":"210","numeric_value":"210","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":"150","numeric_value":"150","unit":"Ω","param_group":"rectifier"}]}],"synced_at":"2026-04-09T05:17:41.080Z"}