{"type_number":"4689","canonical_url":"https://tubeofile.com/tubes/4689","manufacturer":"Philips","tube_type_key":"power_pentode","tube_type_display_name":"Power Pentode","base_name":"P8A","description":"Indirectly-heated steep-slope 18W output pentode. Philips Miniwatt commercial designation for the EL5/375 — a higher voltage-rated variant of the EL5. Designed for Class A or Class A/B push-pull output stages. High mutual conductance (7 mA/V) allows any ordinary AF amplifier valve to fully drive the output stage.","is_directly_heated":false,"completeness":"high","notes":["The 4689 is the Philips commercial designation for the EL5/375. The '/375' suffix indicates 375V max operating anode voltage, compared to 250V for the standard EL5. The 4689 also permits higher screen voltage (275V vs 250V). The max ratings (Wamax = 18W, Ikmax = 90 mA) are shared between both variants.","Philips strongly recommends automatic (cathode) grid bias for this tube. Published operating data for the 4689 relates to constant screen potential of 275V. If a potential divider feeds the screen, the screen voltage will fall as current increases with signal, reducing output power. Philips recommends stabilising the screen voltage with a voltage regulator tube (e.g. type 4687).","The gm and ra values (7 mA/V, 33 kΩ) are from the EL5 datasheet at Va = Vg2 = 250V. At the 4689's higher operating voltages (Va = 375V, Vg2 = 275V), gm may be somewhat higher due to increased space-charge effects.","The EL5 family was Philips' first 18W output pentode (1936), bridging the gap between the 9W generation (EL3N, EL2) and the later Rimlock/Noval types (EL41, EL84). The EL5 was succeeded by the EL61 (Rimlock base).","Heater current is 1.3–1.35A depending on source — too high for series-string heater circuits. Parallel heater supply only."],"references":["https://frank.pocnet.net/sheets/046/4/4689.pdf","https://frank.pocnet.net/sheets/145/e/EL5.pdf"],"source_urls":{"r_type":null,"tdsl":"https://tdsl.duncanamps.com/show.php?des=4689","radiomuseum":"https://www.radiomuseum.org/tubes/tube_4689.html"},"raw_equivalents":["EL5/375","4689P"],"equivalents":[],"similar":[{"type_number":"4689K","reason":"Different base type (Rimlock instead of P8A)","has_detail_page":true},{"type_number":"EL5","reason":"Same P8A base and pinout but lower max operating voltages (Va=250V, Vg2=250V vs 375V/275V for 4689) — not safe as drop-in in higher-voltage 4689 circuits","has_detail_page":true},{"type_number":"EL61","reason":"Successor type on different base — electrically similar but not pin-compatible","has_detail_page":true}],"pins":[{"pin_number":"1","function":"Anode","function_code":"a","notes":null},{"pin_number":"2","function":"Screen Grid (g2)","function_code":"g2","notes":null},{"pin_number":"3","function":"Suppressor Grid (g3, internally connected to cathode)","function_code":"g3","notes":null},{"pin_number":"4","function":"Control Grid (g1)","function_code":"g1","notes":null},{"pin_number":"5","function":"Cathode","function_code":"k","notes":null},{"pin_number":"6","function":"Heater","function_code":"h","notes":null},{"pin_number":"7","function":"Heater","function_code":"h","notes":null},{"pin_number":"8","function":"Internal Connection (screen/beam)","function_code":"ia","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":"375","numeric_value":"375","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","numeric_value":"2","unit":"W","param_group":"absolute_max"},{"key":"Ik_max","display_name":"Cathode Current (max)","value":"90","numeric_value":"90","unit":"mA","param_group":"absolute_max"},{"key":"Vhk_max","display_name":"Heater-to-Cathode Voltage (max)","value":"50","numeric_value":"50","unit":"V","param_group":"absolute_max"},{"key":"Rg_max","display_name":"Max Grid Resistor","value":"0.7","numeric_value":"0.7","unit":"MΩ","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":"-16","numeric_value":"-16","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"72","numeric_value":"72","unit":"mA","param_group":"typical_operating"},{"key":"mAs","display_name":"Screen Current","value":"7.5","numeric_value":"7.5","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"33000","numeric_value":"33000","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"7","numeric_value":"7","unit":"mA/V","param_group":"typical_operating"},{"key":"Rk","display_name":"Cathode Resistor (self-bias)","value":"200","numeric_value":"200","unit":"Ω","param_group":"typical_operating"},{"key":"Pout","display_name":"Output Power","value":"7.7","numeric_value":"7.7","unit":"W","param_group":"output"},{"key":"rl","display_name":"Load Impedance","value":"3500","numeric_value":"3500","unit":"Ω","param_group":"output"},{"key":"Cgp","display_name":"Grid-to-Plate Capacitance","value":"0.8","numeric_value":"0.8","unit":"pF","param_group":"capacitances"}]}],"synced_at":"2026-04-07T12:10:12.026Z"}