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7021

Mercury-vapor negative-control thyratron for grid-controlled rectifier service. Its heavy filament and low-drop discharge support substantial industrial power control.

Directly heatedCold cathodeCommon cathodeDissimilarSpecialized

Sections: 1
Base: 3G
Socket code: B9A
Base pins: 4
Nominal heater: 2.5 V / 5.5 A

Description

RCA 714/7021 is a directly heated gas-and-mercury-vapor negative-control thyratron intended for grid-controlled rectifier service, with 1250-V peak forward and inverse anode ratings and ampere-level current capability.

Socket description

Small-button Noval 9-contact

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base: 3G
Socket code: B9A
Base pins: 4
Nominal heater voltage: 2.5 V
Nominal heater current: 5.5 A
Parallel heater voltage: -
Parallel heater current: -
Series capable: No

3G - Terminal pinout

Electrical assignments shared by every tube using this base designation.

Terminal	Section	Connection	Evidence
PIN1Pin 1	—	F — Filament Transcribed directly from EIA chart; independent cross-check not yet performed.	Unverified EIA Base Connections chart, page 127 (uploaded BaseCodeDataCharts_OCR), base 3G
PIN3Pin 3	A	G1 — Control Grid Transcribed directly from EIA chart; independent cross-check not yet performed.	Unverified EIA Base Connections chart, page 127 (uploaded BaseCodeDataCharts_OCR), base 3G
PIN4Pin 4	—	F — Filament Transcribed directly from EIA chart; independent cross-check not yet performed.	Unverified EIA Base Connections chart, page 127 (uploaded BaseCodeDataCharts_OCR), base 3G
CAP1Top cap	A	P — Plate (Anode) Transcribed directly from EIA chart; independent cross-check not yet performed.	Unverified EIA Base Connections chart, page 127 (uploaded BaseCodeDataCharts_OCR), base 3G

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 A
Rectifier forward voltage drop: 15 V

Gas/mercury-filled grid-controlled rectifier (thyratron).

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

1957 National Electronics

Published operating points and test conditions from this source.

SECTION 1

Thyratron

Other

Maximum DC output current
1 A
Maximum instantaneous output current
3 A
Maximum peak inverse voltage
1250 V
Maximum peak forward voltage
1250 V
Maximum negative grid voltage before conduction
500 V

Characteristic

Filament heating time
5 s
Typical arc drop
15 V

Construction

Filling
Argon/mercury vapor

Application

Service
Industrial grid-controlled rectifier
Service
Timing/control

Capacitance

Anode-grid capacitance
2 pF

Data set 02

1971 RCA HB3 Binder 2 of 7

Published operating points and test conditions from this source.

SECTION 1

Thyratron

Other

Filament voltage
2.5 V
Nominal
Filament current
5 A
Nominal
Maximum deionization time
1000 us
Maximum critical grid current
5 uA
Peak forward anode voltage
1250 V
Peak inverse anode voltage
1250 V
Peak negative grid voltage before conduction
500 V
Peak negative grid voltage during conduction
10 V
Peak anode/cathode current
3 A
Average anode/cathode current
1 A
Fault current
50 A
Short-duration fault rating
Ambient or condensed-mercury operating temperature range
+40 to +80 condensed-mercury operating range C

Characteristic

Minimum heating time prior to tube conduction
5 s
Ionization time
10 us
Approximate
Anode voltage drop
15 V

Capacitance

Grid-to-anode capacitance
2 pF
Approximate