{"type_number":"955","canonical_url":"https://tubeofile.com/tubes/955","manufacturer":null,"tube_type_key":"small_signal_triode","tube_type_display_name":"Small Signal Triode","base_name":"Acorn","description":"Acorn-type miniature triode designed for VHF oscillator and amplifier service at frequencies up to approximately 400 MHz. The acorn construction minimizes lead inductance and inter-electrode capacitance. Widely used in early radar receivers, VHF communications equipment, and laboratory instruments during WWII.","is_directly_heated":false,"completeness":"low","notes":["Acorn-type envelope with radial wire leads — uses special acorn socket (5-pin, JEDEC base 5BC).","Originally designed for VHF/UHF service in early radar and communications equipment during WWII.","MIL-HDBK-213A lists substitutes: 5771, 1650, 467.","Sams Substitution Handbook cross-references 5771, 1650, 467.","TDSL maximum ratings: Va_max = 180V (ICAS), Ia_max = 8 mA.","GE Essential Characteristics lists Va_max = 250V (absolute max) and Pa_max = 1.6W.","The 9001 miniature tube was designed as the B7G replacement for the 955 acorn."],"references":["https://frank.pocnet.net/sheets/049/9/955.pdf"],"source_urls":{"r_type":null,"tdsl":"https://tdsl.duncanamps.com/show.php?des=955","radiomuseum":"https://www.radiomuseum.org/tubes/tube_955.html"},"raw_equivalents":["CV1059","VR59","VT121","5771","1650","467","UN955"],"equivalents":[],"similar":[{"type_number":"6J4","reason":"Later miniature (B7G) VHF triode replacing acorn types — different base and pinout","has_detail_page":true},{"type_number":"9001","reason":"Miniature (all-glass B7G) replacement for the 955 acorn triode — different base, not pin-compatible","has_detail_page":false}],"pins":[],"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":"0.15","numeric_value":"0.15","unit":"A","param_group":"heater"}],"sections":[{"section_number":1,"section_label":"Triode","tube_type_key":"small_signal_triode","specs":[{"key":"Va_max","display_name":"Anode Voltage (max)","value":"250","numeric_value":"250","unit":"V","param_group":"absolute_max"},{"key":"Pa_max","display_name":"Anode Dissipation (max)","value":"1.6","numeric_value":"1.6","unit":"W","param_group":"absolute_max"},{"key":"Ik_max","display_name":"Cathode Current (max)","value":"8","numeric_value":"8","unit":"mA","param_group":"absolute_max"},{"key":"Va","display_name":"Anode Voltage (typical)","value":"180","numeric_value":"180","unit":"V","param_group":"typical_operating"},{"key":"Vg","display_name":"Grid 1 Bias Voltage","value":"-9","numeric_value":"-9","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"4.5","numeric_value":"4.5","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"12500","numeric_value":"12500","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"2.0","numeric_value":"2","unit":"mA/V","param_group":"typical_operating"},{"key":"mu","display_name":"Amplification Factor (μ)","value":"25","numeric_value":"25","unit":"—","param_group":"typical_operating"}]}],"synced_at":"2026-04-07T12:35:07.118Z"}