{"type_number":"EF53","canonical_url":"https://tubeofile.com/tubes/EF53","manufacturer":"Philips","tube_type_key":"ss_pentode","tube_type_display_name":"Small Signal Pentode","base_name":"Loctal","description":"Sharp-cutoff RF pentode on B9G (Loctal) base for use as RF and IF amplifier. Improved version of the EF50 (VR91) with better characteristics, designated VR91A in British military service. Used in radar and communications equipment during and after WWII.","is_directly_heated":false,"completeness":"high","notes":["The EF53 is an improved version of the EF50 with higher gm and better noise performance.","B9G (Loctal) base has a central locating spigot and locking mechanism — requires the correct Loctal socket.","Pin 5 (metallising/shield) must be grounded for proper screening and lowest noise.","Widely used in British military radar equipment as VR91A during WWII.","Datasheet not available from frank.pocnet.net; specifications from Philips published data and cross-referenced with Brans Vademecum and valve equivalents references."],"references":["https://tdsl.duncanamps.com/show.php?des=EF53","https://www.radiomuseum.org/tubes/?tube=EF53"],"source_urls":{"r_type":null,"tdsl":"https://tdsl.duncanamps.com/show.php?des=EF53","radiomuseum":"https://www.radiomuseum.org/tubes/tube_ef53.html"},"raw_equivalents":["VR91A"],"equivalents":[],"similar":[{"type_number":"EF50","reason":"Earlier version (VR91) — same B9G base but inferior performance and higher noise; not all circuits will work with direct substitution","has_detail_page":true},{"type_number":"EF54","reason":"Similar B9G pentode with different operating point — verify characteristics before substituting","has_detail_page":true},{"type_number":"EF91","reason":"Functional successor on B7G miniature base — different pinout, not plug-compatible","has_detail_page":true}],"pins":[{"pin_number":"1","function":"Suppressor Grid (g3)","function_code":"g3","notes":null},{"pin_number":"2","function":"Heater","function_code":"h","notes":null},{"pin_number":"3","function":"Anode","function_code":"a","notes":null},{"pin_number":"4","function":"Control Grid (g1)","function_code":"g1","notes":null},{"pin_number":"5","function":"Metallising / Screen","function_code":"ia","notes":null},{"pin_number":"6","function":"Cathode","function_code":"k","notes":null},{"pin_number":"7","function":"Heater","function_code":"h","notes":null},{"pin_number":"8","function":"Screen Grid (g2)","function_code":"g2","notes":null},{"pin_number":"9","function":"Loctal spigot (no connection)","function_code":"nc","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":"0.2","numeric_value":"0.2","unit":"A","param_group":"heater"}],"sections":[{"section_number":1,"section_label":"Pentode","tube_type_key":"ss_pentode","specs":[{"key":"Va_max","display_name":"Anode Voltage (max)","value":"300","numeric_value":"300","unit":"V","param_group":"absolute_max"},{"key":"Vs_max","display_name":"Screen Voltage (max)","value":"200","numeric_value":"200","unit":"V","param_group":"absolute_max"},{"key":"Pa_max","display_name":"Anode Dissipation (max)","value":"2.5","numeric_value":"2.5","unit":"W","param_group":"absolute_max"},{"key":"Ps_max","display_name":"Screen Dissipation (max)","value":"0.5","numeric_value":"0.5","unit":"W","param_group":"absolute_max"},{"key":"Vhk_max","display_name":"Heater-to-Cathode Voltage (max)","value":"100","numeric_value":"100","unit":"V","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":"150","numeric_value":"150","unit":"V","param_group":"typical_operating"},{"key":"Vg","display_name":"Grid 1 Bias Voltage","value":"-2","numeric_value":"-2","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"10","numeric_value":"10","unit":"mA","param_group":"typical_operating"},{"key":"mAs","display_name":"Screen Current","value":"3.5","numeric_value":"3.5","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"500000","numeric_value":"500000","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"6.5","numeric_value":"6.5","unit":"mA/V","param_group":"typical_operating"}]}],"synced_at":"2026-04-07T12:41:05.306Z"}