{"type_number":"EL50","canonical_url":"https://tubeofile.com/tubes/EL50","manufacturer":"Philips","tube_type_key":"power_pentode","tube_type_display_name":"Power Pentode","base_name":"B8A","description":"AF output power pentode; indirect heated. European side-contact base (P8A/Ct8) with top-cap anode. Developed by Philips, introduced November 1940. Electrically identical to 4654.","is_directly_heated":false,"completeness":"high","notes":["European side-contact base (P8A/Ct8) with top-cap anode — no direct American or Octal/Noval equivalents exist.","The EL50 sits in a large Philips ~18W power pentode family spanning multiple base types: EL5/EL50 (P8A), EL35 (Octal), EL11 (G8A Stahlröhre), EL12 (P8 variants). All share similar electricals (Pa=18W, Va~375V, Gm~7-9 mA/V) but different sockets.","CV2941 is the British military designation. BF451 is listed as equivalent in the Brans Vademecum.","The EL50 belongs to the Philips all-glass P8A tube family that includes the EF50 RF pentode — described as 'next to the magnetron, the most important tube from World War II.' The EF50 was critical to British Chain Home radar; its pressed-glass base technology (shared with the EL50) was a Philips innovation that became the basis for all modern tube construction. Components for the EF50 were smuggled out of the Philips factory in Eindhoven on the eve of the German invasion of the Netherlands in May 1940."],"references":["http://www.r-type.org/exhib/aai0054.htm","https://www.radiomuseum.org/tubes/tube_el50.html","https://www.dos4ever.com/EF50/EF50.html"],"source_urls":{"r_type":"http://www.r-type.org/exhib/aai0054.htm","tdsl":"https://tdsl.duncanamps.com/show.php?des=EL50","radiomuseum":"https://www.radiomuseum.org/tubes/tube_el50.html"},"raw_equivalents":["4654","4654P","4699","4699N","CV2941","BF451","10E/131"],"equivalents":[],"similar":[{"type_number":"4689","reason":"EL5/375 — same P8A base, higher voltage rating than EL5, electrically very close to EL50","has_detail_page":true},{"type_number":"6L6","reason":"American equivalent by function (~18W beam tetrode) but Octal base and beam tetrode vs true pentode","has_detail_page":true},{"type_number":"EL11","reason":"Same electrical class (~18W pentode) but G8A Stahlröhre base — completely different socket","has_detail_page":true},{"type_number":"EL12","reason":"Same ~18W Philips pentode family, P8 base — different pin assignment, not drop-in","has_detail_page":true},{"type_number":"EL34","reason":"Later Philips power pentode (25W), Octal base — higher ratings, different socket","has_detail_page":true},{"type_number":"EL35","reason":"Same ~18W Philips pentode family but Octal (I/O) base — not P8A compatible","has_detail_page":true},{"type_number":"EL37","reason":"Higher-rated Philips pentode (~25W), Octal base — not P8A compatible","has_detail_page":true},{"type_number":"EL39","reason":"Octal base version with similar ratings — not pin-compatible with P8A/B8A base","has_detail_page":true},{"type_number":"EL3N","reason":"Earlier P8 base pentode, lower ratings and different pin assignment","has_detail_page":true},{"type_number":"EL5","reason":"Same P8A base and pinout but lower max operating voltage (250V vs 375V) — not safe in EL50's higher-voltage circuits","has_detail_page":true},{"type_number":"EL54","reason":"Same power class, P8 base — verify pin assignment before substituting","has_detail_page":true}],"pins":[{"pin_number":"1","function":"No Connection","function_code":"nc","notes":null},{"pin_number":"2","function":"Heater","function_code":"h","notes":null},{"pin_number":"3","function":"Heater","function_code":"h","notes":null},{"pin_number":"4","function":"Cathode","function_code":"k","notes":null},{"pin_number":"5","function":"Suppressor Grid (g3)","function_code":"g3","notes":null},{"pin_number":"6","function":"Control Grid (g1)","function_code":"g1","notes":null},{"pin_number":"7","function":"Screen Grid (g2)","function_code":"g2","notes":null},{"pin_number":"8","function":"No Connection","function_code":"nc","notes":null},{"pin_number":"top","function":"Anode (top cap)","function_code":"a","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":"1.35","numeric_value":"1.35","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":"600","numeric_value":"600","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":"Ps_max","display_name":"Screen Dissipation (max)","value":"2.5","numeric_value":"2.5","unit":"W","param_group":"absolute_max"},{"key":"Va","display_name":"Anode Voltage (typical)","value":"375","numeric_value":"375","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":"-17.5","numeric_value":"-17.5","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"48","numeric_value":"48","unit":"mA","param_group":"typical_operating"},{"key":"mAs","display_name":"Screen Current","value":"9","numeric_value":"9","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"},{"key":"rl","display_name":"Load Impedance","value":"3500","numeric_value":"3500","unit":"Ω","param_group":"output"}]}],"synced_at":"2026-04-07T12:45:30.250Z"}