{"type_number":"6528","canonical_url":"https://tubeofile.com/tubes/6528","manufacturer":"Tung-Sol","tube_type_key":"power_triode","tube_type_display_name":"Power Triode","base_name":"Octal","description":"Medium-mu twin power triode developed for use as a passing tube in series regulated power supplies. Features zirconium-coated graphite anodes supported by ceramic insulators, gold-plated molybdenum grid wires, and flexible metal vibration snubbers. Very high transconductance (37,000 umhos) at relatively low plate voltages.","is_directly_heated":false,"completeness":"high","notes":["Designed exclusively as a series pass tube for voltage regulators, not as an audio output tube. No load impedance or output power data is published — regulator service does not use a conventional load line.","One 6528 replaces two or three 6080WA or three or four beam power tubes in regulator circuits.","When sections are paralleled, minimum cathode resistance per cathode leg shall be 10 ohms or the resistance necessary to provide 10% of the grid bias voltage, whichever is greater.","A grid resistor of 1,000 ohms is recommended per triode section to prevent parasitic oscillation while remaining low enough to avoid loss of control from gas current.","A 30-second cathode warmup time is recommended before plate voltage is applied. This is critical in circuits where the amplifier tube plate resistor is returned to the plate side of the passing tube — during warmup the grid is effectively tied to the plate and may draw excessive current.","Heater draws 5.0 A at 6.3 V (31.5 W) — requires a dedicated or heavy-duty heater supply. When connecting many high-drain tube heaters across a single transformer, use bus bars feeding from alternate ends with a stranded pair feeding individual sockets.","Plate current per plate cannot exceed 300 mA if tube voltage drop is to be swung more than 6 volts.","Data marked 'Tentative Data' on the Tung-Sol datasheet (April 1958) — the tube was registered with RETMA in September 1957."],"references":["https://frank.pocnet.net/sheets/127/6/6528.pdf","https://frank.pocnet.net/sheets/115/6/6528.pdf","https://www.radiomuseum.org/tubes/tube_6528.html"],"source_urls":{"r_type":null,"tdsl":"https://tdsl.duncanamps.com/show.php?des=6528","radiomuseum":"https://www.radiomuseum.org/tubes/tube_6528.html"},"raw_equivalents":["CV9094"],"equivalents":[],"similar":[{"type_number":"6080","reason":"Same pinout but much lower current capability (125 mA/plate vs 300 mA/plate) and lower gm","has_detail_page":true},{"type_number":"6336","reason":"Same pinout but much lower mu and gm","has_detail_page":false},{"type_number":"6336A","reason":"Same pinout but much lower mu (2.7 vs 9.0) and gm (13,500 vs 37,000 umhos)","has_detail_page":false},{"type_number":"6336B","reason":"Same pinout but much lower mu (2.7 vs 9.0) and gm (13,500 vs 37,000 umhos)","has_detail_page":true},{"type_number":"6AS7G","reason":"Same pinout but much lower current capability (125 mA/plate vs 300 mA/plate) and lower gm","has_detail_page":true}],"pins":[{"pin_number":"1","function":"Grid (Section 2)","function_code":"g1_2","notes":null},{"pin_number":"2","function":"Plate (Section 2)","function_code":"a2","notes":null},{"pin_number":"3","function":"Cathode (Section 2)","function_code":"k2","notes":null},{"pin_number":"4","function":"Grid (Section 1)","function_code":"g1_1","notes":null},{"pin_number":"5","function":"Plate (Section 1)","function_code":"a1","notes":null},{"pin_number":"6","function":"Cathode (Section 1)","function_code":"k1","notes":null},{"pin_number":"7","function":"Heater","function_code":"h","notes":null},{"pin_number":"8","function":"Heater","function_code":"h","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":"5.0","numeric_value":"5","unit":"A","param_group":"heater"}],"sections":[{"section_number":1,"section_label":"Triode","tube_type_key":"power_triode","specs":[{"key":"Va_max","display_name":"Anode Voltage (max)","value":"400","numeric_value":"400","unit":"V","param_group":"absolute_max"},{"key":"Pa_max","display_name":"Anode Dissipation (max)","value":"30","numeric_value":"30","unit":"W","param_group":"absolute_max"},{"key":"Vhk_max","display_name":"Heater-to-Cathode Voltage (max)","value":"300","numeric_value":"300","unit":"V","param_group":"absolute_max"},{"key":"Rg_max","display_name":"Max Grid Resistor","value":"0.05","numeric_value":"0.05","unit":"MΩ","param_group":"absolute_max"},{"key":"Va","display_name":"Anode Voltage (typical)","value":"100","numeric_value":"100","unit":"V","param_group":"typical_operating"},{"key":"Vg","display_name":"Grid 1 Bias Voltage","value":"-4","numeric_value":"-4","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"300","numeric_value":"300","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"245","numeric_value":"245","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"37","numeric_value":"37","unit":"mA/V","param_group":"typical_operating"},{"key":"mu","display_name":"Amplification Factor (μ)","value":"9.0","numeric_value":"9","unit":"—","param_group":"typical_operating"},{"key":"Cgp","display_name":"Grid-to-Plate Capacitance","value":"23.8","numeric_value":"23.8","unit":"pF","param_group":"capacitances"},{"key":"Cgk","display_name":"Grid-to-Cathode Capacitance","value":"17.8","numeric_value":"17.8","unit":"pF","param_group":"capacitances"},{"key":"Cak","display_name":"Anode-to-Cathode Capacitance","value":"2.9","numeric_value":"2.9","unit":"pF","param_group":"capacitances"},{"key":null,"display_name":"Section 1 Plate to Section 2 Plate Capacitance","value":"0.6","numeric_value":"0.6","unit":"pF","param_group":null},{"key":null,"display_name":"Heater to Cathode Capacitance","value":"15.0","numeric_value":"15","unit":"pF","param_group":null}]}],"synced_at":"2026-04-07T19:01:47.421Z"}