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Power - Tetrode Single (NOT beam) (under 10W) ·Tetrode

418A

Indirectly heated power tetrode designed primarily for broadband video and intermediate-frequency amplifier output stages. Its output capability combines substantial load drive with wide frequency response.

Directly heatedCold cathodeCommon cathodeDissimilar
Sections
1
Base
-
Socket code
UX4
Base pins
4
Nominal heater
6.3 V / 600 mA

Description

Indirectly heated tetrode designed primarily as a power-output tube in broadband video and intermediate-frequency amplifiers.

Socket description

Medium-shell UX 4-contact

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base
-
Socket code
UX4
Base pins
4
Nominal heater voltage
6.3 V
Nominal heater current
600 mA
Parallel heater voltage
-
Parallel heater current
-
Series capable
No

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

Tetrode

X-ray radiationInterelectrode capacitances
Plate resistance
18000 Ω
Transconductance
0.0265 S
Max plate voltage
250 V
Max screen voltage
150 V
Max plate dissipation
8.5 W
Max screen dissipation
3 W
Max cathode current
90 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

Tetrode

Characteristic

  • Heater Voltage . . v ¢ v

    4 volts

    Heater Voltage . . v ¢ v 4 4 v 4 4 4 4 4 4 0 o o o o o o o o o 6.3 volts

  • Cathode Current . . ./Ep =Ec

    150 milliamperes

    Cathode Current . . ./Ep =Ec2 =150 volte Y. + + + &+ &+ « . . T0 milliamperes

  • Plate Voltage o+ o ¢ « «

    4 volts

    Plate Voltage o+ o ¢ « « 4 o ¢ 2 ¢ o o o & & & o ¢ ¢ « & = » » = 250 volts

  • Cathode CUrrent + + o+ & o

    4 milliamperes

    Cathode CUrrent + + o+ & o 4 @ o & & o s o s « = o = 2 2 « s « = 90 milliamperes

  • Heater-Cathode VOltage .+ & ¢ ¢ ¢ o &

    4 volts

    Heater-Cathode VOltage .+ & ¢ ¢ ¢ o & 4 = o = o o 2 o # « « « =« 90 volts

  • For Cathcde Bias . &

    4 megohm

    For Cathcde Bias . & 4 & v & ¢ 4 ¢ 2 ¢ o a s « o a o o o o » 0.10 megohm

  • Plate Voltage « ¢ + & v v v

    4 volts

    Plate Voltage « ¢ + & v v v 4 v v v v ¢ ¢ & & & » 120 150 volts

  • Screen Grid Voltage . . + « & & v

    4 volts

    Screen Grid Voltage . . + « & & v 4 4 4 o o o = 120 150 volts

  • Control Grid Voltage .+ +« + « « + o &+ o

    2 volts

    Control Grid Voltage .+ +« + « « + o &+ o 2 o = o -1.0 - volts

  • Plate Current . « . o« o o o « o s o &

    2 milliamperes

    Plate Current . « . o« o o o « o s o & 2 s « = « = 47 50 milliamperes

  • Screen Grid Current . . v« ¢ & &

    4 milliamperes

    Screen Grid Current . . v« ¢ & &+ 4 ¢ 4 « ¢ + o o . 20 20 milliamperes

  • Plate Resistance . . . v v « v ¢« o o« v =« « »

    18000 ohms

    Plate Resistance . . . v v « v ¢« o o« v =« « » - . 18000 18000 ohms

  • Plate Current of

    10 volts

    Plate Current of 10 mMicroamperes .« « + « + « « & -9.5 --- volts

Other

  • Plate Dissipation « v v

    4 watts

    Plate Dissipation « v v 4 = v o 4 4 5 o 4 & = & = o « 4 « v o« 8.5 watts

  • Screen Grid Dissipation + & & v

    4 watts

    Screen Grid Dissipation + & & v 4 & ¢ 40 4 & 4 4 & 4 4 4 .o 3.0 watts