{"type_number":"958A","canonical_url":"https://tubeofile.com/tubes/958A","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 transmitter oscillator service. Battery-operated filament (1.25V/0.1A) suits portable and field transmitter equipment. Improved version of the 958 with tighter specifications.","is_directly_heated":true,"completeness":"low","notes":["Acorn-type envelope with radial wire leads — uses special acorn socket (5-pin, JEDEC base 5BD).","Battery-type filament: 1.25V at 0.1A — designed for portable/field transmitter equipment.","The 958A is an improved version of the 958 with tighter specifications.","TDSL lists CV2701 as close or identical; 958, CV650, VT212 as different rating/performance.","Sams Substitution Handbook cross-references 02C (and reverse: D2C substitutes 958A).","GE Essential Characteristics lists typical operation at Va=135V, Vg=-6V, Ia=1.9mA, gm=650 umhos, Pa_max=0.6W."],"references":["https://frank.pocnet.net/sheets/049/9/958A.pdf"],"source_urls":{"r_type":null,"tdsl":"https://tdsl.duncanamps.com/show.php?des=958A","radiomuseum":"https://www.radiomuseum.org/tubes/tube_958a.html"},"raw_equivalents":["CV2701"],"equivalents":[],"similar":[{"type_number":"955","reason":"Acorn triode with 6.3V heater — same structure (triode) but different heater voltage, not interchangeable","has_detail_page":true},{"type_number":"958","reason":"Original version with slightly different ratings — TDSL lists as 'different rating or performance'","has_detail_page":false}],"pins":[],"specs":[{"key":"Vh","display_name":"Heater Voltage","value":"1.25","numeric_value":"1.25","unit":"V","param_group":"heater"},{"key":"Ah","display_name":"Heater Current","value":"0.1","numeric_value":"0.1","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":"135","numeric_value":"135","unit":"V","param_group":"absolute_max"},{"key":"Pa_max","display_name":"Anode Dissipation (max)","value":"0.6","numeric_value":"0.6","unit":"W","param_group":"absolute_max"},{"key":"Va","display_name":"Anode Voltage (typical)","value":"135","numeric_value":"135","unit":"V","param_group":"typical_operating"},{"key":"Vg","display_name":"Grid 1 Bias Voltage","value":"-6","numeric_value":"-6","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"1.9","numeric_value":"1.9","unit":"mA","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"0.65","numeric_value":"0.65","unit":"mA/V","param_group":"typical_operating"}]}],"synced_at":"2026-04-07T12:35:13.438Z"}