6SF5

Small Signal Triode — Octal

Known Equivalents & Substitutes

6SF5GT6SF5-GTVT-198

Similar Tubes (Not Drop-In Compatible)

Electrically identical 12.6V heater version — same mu, ra, gm, and pinout but different heater voltage (12.6V vs 6.3V)

6SF7

High-mu pentode variant in the same 6S-series family, similar heater and base but pentode structure

6SL7GT

High-mu dual triode with similar mu (~70) and high ra, but dual-section in a different basing arrangement

6SQ7 contains a triode section with similar high-mu characteristics, but also includes two diode sections (duplex-diode triode)

Electrical Specifications

Absolute Maximum

Anode Voltage (max)Anode Voltage (max)300V

Max Grid ResistorMax Grid Resistor10MΩ

Typical Operating

Anode Voltage (typical)Anode Voltage (typical)250V

Grid 1 Bias VoltageGrid Voltage-2V

Notes

Coated unipotential cathode. In circuits where the cathode is not directly connected to the heater, the heater-to-cathode voltage should be kept as low as possible.
Shell is internally connected to cathode (pin 2).
Base designation 6AB (6-pin Octal). GT variant uses G-6AB (intermediate shell, 6-pin Octal).
MIL-HDBK-213A lists 6SF5 as a receiving triode, high-mu. The 6SF5GT is a direct substitute.
Typical application: resistance-coupled Class A1 amplifier. Same operating chart as the 6F5 in resistance-coupled amplifier service.

Pin Layout — Octal

1No Connection

2Cathode (shell)

3Grid

4

Socket-Compatible Tubes ⚠ Not electrically compatible

References