Skip to main content
Tube Tinker — Electron Tube Database
Alternatives & variationsDownload PDF datasheet

Specialized - Thyratron ·Thyratron

393A

Gas-filled grid-controlled thyratron for switching, controlled-rectifier, relay, motor-control, oscillator, or pulse service as documented by the manufacturer.

Directly heatedCold cathodeCommon cathodeDissimilarSpecialized
Sections
1
Base
-
Socket code
B4B
Base pins
7
Nominal heater
2.5 V / 7 A

Description

The 393A is a three-electrode argon and mercury-vapor thyratron with a negative-control characteristic, intended for grid-controlled rectifier, motor-control, and relay applications.

Socket description

Medium 4-pin bayonet

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base
-
Socket code
B4B
Base pins
7
Nominal heater voltage
2.5 V
Nominal heater current
7 A
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

Thyratron

X-ray radiationInterelectrode capacitances
Max plate voltage
1250 V
Max cathode current
1.5 A
Rectifier forward voltage drop
10 V
Rectifier warm-up time
15 s

Three-electrode thyratron; SectionType=Other because Thyratron is not a canonical SectionType. MaxPlateVoltage uses published peak anode voltage; MaxCathodeCurrent uses maximum average cathode current.

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

1956 Western Electric Tubes

Published operating points and test conditions from this source.

SECTION 1

Thyratron

Characteristic

  • HeaterOrFilamentVoltage

    2.5 V

  • HeaterOrFilamentCurrent

    7 A

Other

  • Peak Anode Current

    5 A

  • OperatingTemperatureMinimum

    -40 C

  • OperatingTemperatureMaximum

    80 C

Data set 02

1961 Tung Sol

Published operating points and test conditions from this source.

SECTION 1

Thyratron

Characteristic

  • Filament voltage

    2.5 V

  • Filament current

    7 A

  • Cathode heating time minimum

    15 s

  • Anode voltage drop initial

    10 V

Capacitance

  • Anode to control grid capacitance

    1.8 pF

Other

  • Peak forward anode voltage

    1250 V

  • Peak reverse anode voltage

    1250 V

  • Fault anode current

    120 A

    0.1SecondMax

Data set 03

1966 Tung Sol Electronic Tubes 3 of 4

Published operating points and test conditions from this source.

SECTION 1

Thyratron

Other

  • Peak forward anode voltage

    1250 V

    ThyratronService

  • Peak reverse anode voltage

    1250 V

    ThyratronService

  • Peak anode current

    6 A

    ThyratronService

  • Average anode current

    1.5 A

    ThyratronService

  • Fault anode current

    120 A

    ThyratronService

  • Maximum plate voltage

    1250 V

    PromotedValue

  • Maximum cathode current

    1.5 A

    PromotedValue

  • Forward

    1250 V

    PublishedTable

  • Reverse

    1250 V

    PublishedTable

  • Peak Or Dc Before Tube Conduction

    -500 V

    PublishedTable

  • Average During Tube Conduction --Note 1

    -10 V

    PublishedTable

  • Peak

    6 A

    PublishedTable

  • Average -Note 2

    1.5 A

    PublishedTable

  • Fault-For Duration Of 0.1 Sec. Max. -Note 3

    120 A

    PublishedTable

  • Filament Voltage 2.37

    2.63 V

    PublishedTable

Characteristics

  • Cathode heating time minimum

    15 s

    ThyratronService

  • Anode voltage drop initial

    10 V

    ThyratronService

  • Anode voltage drop end of life

    20 V

    ThyratronService

  • De-ionization time

    360 us

    ThyratronService

  • Rectifier forward voltage drop

    10 V

    PromotedValue

  • Rectifier warmup time

    15 s

    PromotedValue

  • 2 .6±0.125 Volts

    7 A

    PublishedTable

  • Filament Current @ Ef =2.6 Volts

    7 A

    PublishedTable

  • Cathode Heating Time -Minimum

    15 s

    PublishedTable

  • Anode Volts = 120 Anode Current =

    1.6 A

    PublishedTable

  • Initial

    10 V

    PublishedTable

  • End Of Life

    20 V

    PublishedTable

Capacitance

  • Anode-to-control-grid capacitance

    1.8 pF

Data set 04

2026 Western Electric 300s

Published operating points and test conditions from this source.

SECTION 1

Thyratron

Other

  • Peak Cathode Current

    6 A

  • CathodeSurgeCurrent

    120 A

    Maximum duration 0.1 s

  • NegativeGridVoltageBeforeConduction

    500 V

  • NegativeGridVoltageDuringConduction

    10 V

  • PositiveGridCurrentAverage

    10 mA

    Averaging time one cycle

  • Anode Grid Capacitance

    1.8 pF

    Bogey

  • GridFilamentCapacitance

    5.6 pF

    Bogey

  • CondensedMercuryTemperature

    -55 to 80 degC

Characteristic

  • Anode Voltage Drop

    15 V

    Bogey

  • RequiredFilamentHeatingTime

    15 s