6F8G

Small Signal Triode — Octal

Known Equivalents & Substitutes

VT-99CV1917CV19186C8GVT-163

Similar Tubes (Not Drop-In Compatible)

Electrically equivalent Noval double triode (same as 6FQ7) — different base (B9A vs Octal), not pin-compatible

6SN7GT

Direct successor, same electricals but no top cap — different pin topology

Electrical Specifications

Absolute Maximum

Anode Voltage (max)Max Plate Voltage300V

Anode Dissipation (max)Max Plate Dissipation (per unit)2.5W

Cathode Current (max)Max Cathode Current20mA

Heater-to-Cathode Voltage (max)Max Heater-Cathode Voltage90V

Max Grid Resistor

Notes

Each triode section is electrically identical to the 6J5, 6J5G, and 6J5GT; curves under type 6J5 apply to each unit of the 6F8G.
Triode 1 (T1) has its grid brought to base pin 5; Triode 2 (T2) has its grid brought to the top cap. This asymmetric grid connection means the two sections have different interelectrode capacitances.
The 6SN7GT is the direct successor with the same electrical characteristics but in a shouldered GT envelope without a top cap — not a drop-in substitute due to different pinout.
6CG7/6FQ7 are noval-base equivalents with similar characteristics but different base type.
The 6C8G substitute (per Sams) may not work in all circuits and is for parallel-filament circuits only.
Voltage between heater and cathode should be kept at a minimum if direct connection is not possible.

Pin Layout — Octal

1No Connection

2Heater

3Plate T2

4

References