{"type_number":"AL5","canonical_url":"https://tubeofile.com/tubes/AL5","manufacturer":"Philips","tube_type_key":"power_pentode","tube_type_display_name":"Power Pentode","base_name":"P8A","description":"Output pentode with 18 W anode dissipation and 4 V heater; indirectly heated. Philips design from 1936, the 4 V heater version of the EL5. P8A side-contact base with top-cap anode connection. Designed for high-power audio output stages in European AC mains receivers with 4 V heater transformers.","is_directly_heated":false,"completeness":"medium","notes":["The AL5 is the 4 V heater version of the EL5. 'A' prefix = 4 V heater in the Philips naming convention.","Pa_max = 18 W — approximately 8.8 W single-ended output, 20 W push-pull AB at 5% distortion.","Anode connection via top cap. P8A side-contact base.","Standard operation: Va = 250 V, Vg2 = 275 V.","AL5/325 and AL5/375 are voltage-selected variants rated for higher anode voltages."],"references":["Philips Miniwatt 1938 catalogue, page 4"],"source_urls":{"r_type":null,"tdsl":null,"radiomuseum":"https://www.radiomuseum.org/tubes/tube_al5.html"},"raw_equivalents":["WE42","A70E","TAL5","VAL5","4A27"],"equivalents":[],"similar":[{"type_number":"AL5/375","reason":"Factory-selected for 375 V operation — same base, higher voltage rating","has_detail_page":true},{"type_number":"EL12","reason":"Related 18 W pentode with Y8A base — different base, not pin-compatible","has_detail_page":true},{"type_number":"EL35","reason":"Octal-base equivalent of EL5 — different base, not pin-compatible","has_detail_page":true},{"type_number":"EL5","reason":"6.3 V heater version — electrically identical but different heater voltage, not interchangeable","has_detail_page":true}],"pins":[{"pin_number":"1","function":"Control Grid","function_code":"g1","notes":null},{"pin_number":"2","function":"Cathode","function_code":"k","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":"Screen Grid","function_code":"g2","notes":null},{"pin_number":"6","function":"Metallization (external shield)","function_code":"ia","notes":null},{"pin_number":"7","function":"Suppressor Grid (internally connected to cathode)","function_code":"g3","notes":null},{"pin_number":"8","function":"No Connection","function_code":"nc","notes":null},{"pin_number":"TC","function":"Anode (top cap)","function_code":"a","notes":null}],"specs":[{"key":"Vh","display_name":"Heater Voltage","value":"4","numeric_value":"4","unit":"V","param_group":"heater"},{"key":"Ah","display_name":"Heater Current","value":"2","numeric_value":"2","unit":"A","param_group":"heater"}],"sections":[{"section_number":1,"section_label":"Pentode","tube_type_key":"power_pentode","specs":[{"key":"Va_max","display_name":"Anode Voltage (max)","value":"275","numeric_value":"275","unit":"V","param_group":"absolute_max"},{"key":"Vs_max","display_name":"Screen Voltage (max)","value":"275","numeric_value":"275","unit":"V","param_group":"absolute_max"},{"key":"Pa_max","display_name":"Anode Dissipation (max)","value":"18","numeric_value":"18","unit":"W","param_group":"absolute_max"},{"key":"Va","display_name":"Anode Voltage (typical)","value":"250","numeric_value":"250","unit":"V","param_group":"typical_operating"},{"key":"Vs","display_name":"Screen Voltage (typical)","value":"275","numeric_value":"275","unit":"V","param_group":"typical_operating"},{"key":"Vg","display_name":"Grid 1 Bias Voltage","value":"-18","numeric_value":"-18","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"72","numeric_value":"72","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"22000","numeric_value":"22000","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"8.5","numeric_value":"8.5","unit":"mA/V","param_group":"typical_operating"},{"key":"Pout","display_name":"Output Power","value":"8.8","numeric_value":"8.8","unit":"W","param_group":"output"}]}],"synced_at":"2026-04-08T07:54:24.027Z"}