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Voltage Pentode ·Pentode

409A

Miniature triple-grid pentode for low-power HF/UHF applications, with independently controllable suppressor grid supporting gating, mixing, and modulation.

Directly heatedCold cathodeCommon cathodeDissimilar
Sections
1
Base
E7-1
Socket code
B7G
Base pins
7
Nominal heater
6.3 V / 175 mA

Description

The 6AS6/409A is a 7-pin miniature triple-grid pentode with an indirectly heated cathode, intended for low-power high- and ultra-high-frequency applications; its suppressor grid can serve as an independent control element.

Socket description

Miniature 7-contact

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base
E7-1
Socket code
B7G
Base pins
7
Nominal heater voltage
6.3 V
Nominal heater current
175 mA
Parallel heater voltage
-
Parallel heater current
-
Series capable
No

E7-1 - Terminal pinout

Electrical assignments shared by every tube using this base designation.

No verified pinout is recorded for this base designation.

Section ratings

1 physical section, each with unique specifications.

Section 1

Pentode

X-ray radiationInterelectrode capacitances
Transconductance
0.00185 S
Max plate voltage
180 V
Max screen voltage
140 V
Max plate dissipation
1.7 W
Max screen dissipation
0.75 W
Max cathode current
18 mA

Promoted fields mapped from printed maximum-rating and characteristic headings; additional published values preserved in parameter rows.

Source-dependent data

Operating conditions by source

Each block preserves the test conditions and published values from one reference. Values from different sources are intentionally kept separate.

Data set 01

2026 Western Electric 400s

Published operating points and test conditions from this source.

SECTION 1

Pentode

Other

  • Plate dissipation

    1.7 watts

    Plate dissipation 1.7 watts

  • Sereen dissipation

    75 watt

    Sereen dissipation 0,75 watt

Characteristic

  • Cathode current

    18 milliamperes

    Cathode current 18 milliamperes

  • Heater-cathode voltage

    90 volts

    Heater-cathode voltage 90 volts

  • Plate voltage

    120 volts

    Plate voltage 120 120 volts

  • Sereen voltage

    120 volts

    Sereen voltage 120 120 volts

  • Suppresser voltage

    -3 volts

    Suppresser voltage -3 0 volts

  • Grid voltage

    -2 volts

    Grid voltage -2 = 2 volts

  • Sereen current

    4.8 milliamperes

    . Sereen current 4.8 3.5 milliamperes

  • Plate voltage

    120 volts

    Plate voltage 120 volts Plate voltage 120 120 volts

  • Screen voltage

    120 volts

    . Screen voltage 120 volts Sereen voltage 120 60 volts

  • Suppressor voltage

    0 volts

    Suppressor voltage 0 volts Grid voltage - 2 0 volts

  • SCREEN VOLTAGE=

    120 VOLTS

    SCREEN VOLTAGE=120 VOLTS fe——— 14

  • Ef=

    63 VOLTS

    Ef=63 VOLTS PLATE VOLTAGE=120 VOLTS £t =6.3 VOLTS Eci=n

  • H Eci=-i o SCREEN VOLTAGE

    120 VOLTS

    H Eci=-i o SCREEN VOLTAGE 120 VOLTS

  • " Ef=

    63 VOLTS

    " Ef=63 VOLTS Eciz - \ SCREEN VOLTAGE«I20VOLTS

  • W

    5000 VOLTS

    W 5000 PLATE VOLTAGE =120 VOLTS |

  • GRID VOLTAGE. £¢ =~/ E

    63 VOLTS

    GRID VOLTAGE. £¢ =~/ E4=63 VOLTS

  • Published value

    1400 VOLTS

    1400 AN PLATE VOLTAGE =120 VOLTS

  • / \ SCREEN VOLTAGE =i

    20 VOLTS

    / \ SCREEN VOLTAGE =i 20 VOLTS

Data set 02

2026 Western Electric Other

Published operating points and test conditions from this source.

SECTION 1

Pentode

Other

  • Heater Voltage

    6.3 V

    A-C or D-C

  • Heater Current Nominal

    175 mA

    Nominal

  • Plate Voltage Maximum

    180 V

    Design-center value

  • Screen Voltage Maximum

    140 V

    Design-center value

  • Positive Suppressor Voltage Maximum

    27 V

    Design-center value

  • Plate Dissipation Maximum

    1.7 W

    Design-center value

  • Screen Dissipation Maximum

    0.75 W

    Design-center value

  • Cathode Current Maximum

    18 mA

    Design-center value

  • Heater-Cathode Voltage Maximum

    90 V

    Design-center value

  • Bulb Temperature Maximum

    120 degC

    Design-center value

  • Plate Voltage

    120 V

    Suppressor -3 V

  • Screen Voltage

    120 V

    Suppressor -3 V

  • Suppressor Voltage

    -3 V

    Operating column 1

  • Control Grid Voltage

    -2 V

    Operating column 1

  • Plate Voltage

    120 V

    Suppressor 0 V

  • Screen Voltage

    120 V

    Suppressor 0 V

  • Suppressor Voltage

    0 V

    Operating column 2

  • Control Grid Voltage

    -2 V

    Operating column 2

Characteristic

  • Plate Current

    3.6 mA

    Operating column 1

  • Screen Current

    4.8 mA

    Operating column 1

  • Control-Grid Transconductance

    1850 uS

    Operating column 1

  • Suppressor-Grid Transconductance

    810 uS

    Operating column 1

  • Plate Current

    5.2 mA

    Operating column 2

  • Screen Current

    3.5 mA

    Operating column 2

  • Control-Grid Transconductance

    3200 uS

    Operating column 2

  • Suppressor-Grid Transconductance

    470 uS

    Operating column 2

  • Control-Grid Cutoff Nominal

    -6 V

    Plate 120 V; screen 120 V; suppressor 0 V

  • Control-Grid Cutoff Guaranteed

    -10 V

    Plate 120 V; screen 120 V; suppressor 0 V

  • Suppressor-Grid Cutoff Nominal

    -10 V

    Plate 120 V; screen 120 V; control grid -2 V

  • Suppressor-Grid Cutoff Guaranteed

    -15 V

    Plate 120 V; screen 120 V; control grid -2 V

Capacitance

  • Control-grid to heater/cathode/screen/suppressor capacitance

    3.9 pF

    JAN 1A No. 314 shield connected to cathode

  • Plate to control-grid capacitance

    0.01 pF

    JAN 1A No. 314 shield connected to cathode

  • Plate to heater/cathode/screen/suppressor capacitance

    3 pF

    JAN 1A No. 314 shield connected to cathode

  • Control-grid to suppressor-grid capacitance

    0.1 pF

    JAN 1A No. 314 shield connected to cathode