{"type_number":"AL3","canonical_url":"https://tubeofile.com/tubes/AL3","manufacturer":"Philips","tube_type_key":"power_pentode","tube_type_display_name":"Power Pentode","base_name":"P8A","description":"Output pentode for audio amplifiers; indirectly heated with 4 V heater. Original Philips 'red series' design from 1935 with P8A side-contact base and top-cap anode connection. The 4 V heater version of the EL3 family, designed for European AC mains receivers with 4 V heater transformers. Superseded by the AL4 in 1936.","is_directly_heated":false,"completeness":"medium","notes":["The AL3 is the 4 V heater version of the EL3. 'A' prefix = 4 V heater in the Philips naming convention.","Withdrawn and replaced by the AL4 (improved profiled cathode) in 1936.","Anode connection via top cap. P8A side-contact base carries heater, cathode, grids, and metallization.","Cathode-bias only — fixed bias is prohibited per the Philips datasheet.","gm of 9 mA/V — significantly higher than earlier types (2.5 mA/V).","Found in 86 radio models from 1935-1938."],"references":["https://tdsl.duncanamps.com/show.php?des=AL3","https://www.radiomuseum.org/tubes/?tube=AL3"],"source_urls":{"r_type":null,"tdsl":"https://tdsl.duncanamps.com/show.php?des=AL3","radiomuseum":"https://www.radiomuseum.org/tubes/tube_al3.html"},"raw_equivalents":["TL3","TAL3","VAL3","TL34","UAL3"],"equivalents":[],"similar":[{"type_number":"AL4","reason":"Improved successor with profiled cathode (1936) — same P8A base, higher efficiency","has_detail_page":true},{"type_number":"EL3","reason":"6.3 V heater version — electrically identical but different heater voltage, not interchangeable","has_detail_page":true},{"type_number":"EL3N","reason":"6.3 V heater improved version — different heater voltage","has_detail_page":true},{"type_number":"PenA4","reason":"Different base with slightly different data","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":"1.85","numeric_value":"1.85","unit":"A","param_group":"heater"},{"key":"Va_max","display_name":"Anode Voltage (max)","value":"250","numeric_value":"250","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":"9","numeric_value":"9","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":"250","numeric_value":"250","unit":"V","param_group":"typical_operating"},{"key":"Vg","display_name":"Grid 1 Bias Voltage","value":"-6","numeric_value":"-6","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"36","numeric_value":"36","unit":"mA","param_group":"typical_operating"},{"key":"mAs","display_name":"Screen Current","value":"4","numeric_value":"4","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"50000","numeric_value":"50000","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"9","numeric_value":"9","unit":"mA/V","param_group":"typical_operating"},{"key":"Pout","display_name":"Output Power","value":"4.5","numeric_value":"4.5","unit":"W","param_group":"output"}],"sections":[{"section_number":1,"section_label":"Pentode","tube_type_key":"power_pentode","specs":[{"key":"Va_max","display_name":"Anode Voltage (max)","value":"250","numeric_value":"250","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":"9","numeric_value":"9","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":"250","numeric_value":"250","unit":"V","param_group":"typical_operating"},{"key":"Vg","display_name":"Grid 1 Bias Voltage","value":"-6","numeric_value":"-6","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"36","numeric_value":"36","unit":"mA","param_group":"typical_operating"},{"key":"mAs","display_name":"Screen Current","value":"4","numeric_value":"4","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"50000","numeric_value":"50000","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"9","numeric_value":"9","unit":"mA/V","param_group":"typical_operating"},{"key":"Rk","display_name":"Cathode Resistor (self-bias)","value":"150","numeric_value":"150","unit":"Ω","param_group":"typical_operating"},{"key":"Pout","display_name":"Output Power","value":"4.5","numeric_value":"4.5","unit":"W","param_group":"output"},{"key":"rl","display_name":"Load Impedance","value":"7000","numeric_value":"7000","unit":"Ω","param_group":"output"}]}],"synced_at":"2026-04-07T12:35:27.315Z"}