6S4A — Small Signal Triode, Noval | Tubeofile

6S4A

Small Signal Triode — Noval

Tung-Sol

Known Equivalents & Substitutes

6S4

Electrical Specifications

Absolute Maximum

Anode Voltage (max)DC Plate Voltage (max)550V

Peak Anode Voltage (max)Peak Positive Plate Voltage (abs max)2,200V

Anode Dissipation (max)Plate Dissipation (max)8.5W

Cathode Current (max)Average Cathode Current (max)30mA

Heater-to-Cathode Voltage (max)Peak Heater-Cathode Voltage (max)200V

Max Grid ResistorGrid Circuit Resistance (cathode bias, max)2.2MΩ

Typical Operating

Anode Voltage (typical)Plate Voltage250V

Grid 1 Bias VoltageGrid Voltage-8V

Anode CurrentPlate Current24mA

Anode ResistancePlate Resistance3,700Ω

TransconductanceTransconductance

Capacitances

Grid-to-Plate CapacitanceGrid to Plate Capacitance2.4pF

Grid-to-Cathode CapacitanceGrid to Cathode and Heater Capacitance4.2pF

Output CapacitancePlate to Cathode and Heater Capacitance0.6pF

Heater

Heater VoltageHeater Voltage6.3V

Heater CurrentHeater Current0.6A

Notes

6S4A is identical to 6S4 electrically; only heater thermal characteristics differ (controlled warm-up time). TDSL lists 6S4 as a 'different rating or performance' substitute.
Base is Small-Button Noval 9-Pin (JEDEC No. E9-1), basing designation 9AC. Pins 1, 7, and 8 are internal connections — do not use.
Philips interchange guide lists 6S4 -> 6S4A and 6S4A -> 6S4A (self-replacement).
MIL-HDBK-213A classifies as 'Receiving triode, miniature' and cross-references 6S4A as an other number for 6S4.
Brans Vademecum table IIIf lists 6S4 with equivalents 6BJ8 and 7AU7.
GE Essential Characteristics lists a max plate dissipation of 7.5 W for the 6S4; the Tung-Sol and RCA datasheets for 6S4A specify 8.5 W. The datasheet value of 8.5 W is used here.
The peak positive plate voltage rating of 2200 V reflects vertical-deflection service where flyback pulses are present.
Heater warm-up time is 11 seconds (defined as time to reach 80% of rated voltage across heater in a specified test circuit).

Pin Layout — Noval

1Internal Connection

2Cathode

3Grid

References