{"type_number":"E55L","canonical_url":"https://tubeofile.com/tubes/E55L","manufacturer":"Mullard","tube_type_key":"power_pentode","tube_type_display_name":"Power Pentode","base_name":"Magnoval","description":"Special quality high-slope frame-grid power pentode for wideband video output and industrial applications. Designed by Mullard/Philips circa 1960 for use in oscilloscope vertical amplifiers, professional audio, and measurement equipment. Features exceptionally high transconductance (45 mA/V) for a power pentode, with beam-forming plates internally despite being classified as a pentode. Gold-plated base pins for low contact resistance.","is_directly_heated":false,"completeness":"high","notes":["The Mullard datasheet provides two sets of absolute maximum ratings: normal life (Va_max=200V, Ik_max=70mA) and reduced life (Ik_max=100mA, bulb temp 220°C vs 180°C normal).","Despite being classified as a pentode, internal inspection reveals beam-forming plates within the anode cavity. The screen grid is formed from parallel fine wires; the control grid is a frame-grid construction extremely close to the cathode.","The typical operating point (Va=200V, Vg2=175V, Vg1=-55V) yields Ia=50mA with Ig2=5.5mA and gm=45mA/V — an unusually high transconductance for a power pentode.","Widely used in Tektronix oscilloscopes as the Y-amplifier final stage driving CRT deflection plates.","Va_max of 400V applies to the absolute maximum rating; the typical operating condition uses Va=200V.","Pins 2 and 6 are both suppressor grid (g3) connections, internally connected to cathode. Pins 7 and 9 are both cathode connections."],"references":["https://frank.pocnet.net/sheets/030/e/E55L.pdf","https://tdsl.duncanamps.com/show.php?des=E55L","https://www.r-type.org/exhib/aaa0271.htm"],"source_urls":{"r_type":"https://www.r-type.org/exhib/aaa0271.htm","tdsl":"https://tdsl.duncanamps.com/show.php?des=E55L","radiomuseum":"https://www.radiomuseum.org/tubes/tube_e55l.html"},"raw_equivalents":["8233","CV5808"],"equivalents":[],"similar":[{"type_number":"8608","reason":"Electrically equivalent power pentode on Magnoval base — identical characteristics but anode on top cap instead of base pin 1, not pin-compatible","has_detail_page":true}],"pins":[{"pin_number":"1","function":"Anode","function_code":"a","notes":null},{"pin_number":"2","function":"Suppressor Grid (g3)","function_code":"g3","notes":null},{"pin_number":"3","function":"Screen Grid (g2)","function_code":"g2","notes":null},{"pin_number":"4","function":"Heater","function_code":"h","notes":null},{"pin_number":"5","function":"Heater","function_code":"h","notes":null},{"pin_number":"6","function":"Suppressor Grid (g3)","function_code":"g3","notes":null},{"pin_number":"7","function":"Cathode","function_code":"k","notes":null},{"pin_number":"8","function":"Control Grid (g1)","function_code":"g1","notes":null},{"pin_number":"9","function":"Cathode","function_code":"k","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":"0.6","numeric_value":"0.6","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":"400","numeric_value":"400","unit":"V","param_group":"absolute_max"},{"key":"Vs_max","display_name":"Screen Voltage (max)","value":"175","numeric_value":"175","unit":"V","param_group":"absolute_max"},{"key":"Pa_max","display_name":"Anode Dissipation (max)","value":"10","numeric_value":"10","unit":"W","param_group":"absolute_max"},{"key":"Ik_max","display_name":"Cathode Current (max)","value":"70","numeric_value":"70","unit":"mA","param_group":"absolute_max"},{"key":"Va","display_name":"Anode Voltage (typical)","value":"200","numeric_value":"200","unit":"V","param_group":"typical_operating"},{"key":"Vs","display_name":"Screen Voltage (typical)","value":"175","numeric_value":"175","unit":"V","param_group":"typical_operating"},{"key":"Vg","display_name":"Grid 1 Bias Voltage","value":"-55","numeric_value":"-55","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"50","numeric_value":"50","unit":"mA","param_group":"typical_operating"},{"key":"mAs","display_name":"Screen Current","value":"5.5","numeric_value":"5.5","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"20000","numeric_value":"20000","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"45","numeric_value":"45","unit":"mA/V","param_group":"typical_operating"},{"key":"Rk","display_name":"Cathode Resistor (self-bias)","value":"270","numeric_value":"270","unit":"Ω","param_group":"typical_operating"}]}],"synced_at":"2026-04-07T12:37:39.828Z"}