STC equivalent — electrically identical per STC datasheet (same gm, ra, ratings), but uses Loctal (B8G) 8-pin base instead of Magnoval (B9D) 9-pin. Not pin-compatible.
Input CapacitanceInput Capacitance (g to h+k+i.s.)11.1pF
Output CapacitanceOutput Capacitance (p to h+k+i.s.)1pF
Heater
Heater VoltageHeater Voltage6.3V
Heater CurrentHeater Current0.45A
Notes
Developed by Bell Telephone Laboratories for the AT&T L-3 coaxial carrier system. First issued October 1955 (Bell System Practices AB46.437A, Issue 1).
Uses Magnoval (B9D) 9-pin base with T9 bulb envelope. Pins 3, 7, and 9 are no connection.
The datasheet specifies three typical operating conditions: Eb=140V (Ia=29 mA), Eb=180V (Ia=25 mA), and Eb=160V with cathode bias (Ia=36.5 mA, Rk=262 ohms, Ec1=+7.5V supply). The third condition is the primary L-3 amplifier design point.
Operation with control grid positive with respect to cathode is not recommended (Note 1).
Grid circuit resistance is very low: 0.05 Mohm for fixed bias, 0.10 Mohm for cathode bias — typical of high-gm types.
Two cathode pins (6 and 8) provided for reduced lead inductance.