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

3A4

Directly heated power pentode for oscillator, Class-A audio, or Class-C RF power service. Series/parallel filament operation supports portable equipment, with documented output around one watt under suitable conditions.

Directly heatedCold cathodeCommon cathodeDissimilar
Sections
1
Base
7B8
Socket code
B7G
Base pins
7
Nominal heater
1.4 V / 200 mA

Description

Power pentode for oscillator or Class A amplifier service, with series or parallel filament operation.

Socket description

Miniature 7-contact

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base
7B8
Socket code
B7G
Base pins
7
Nominal heater voltage
1.4 V
Nominal heater current
200 mA
Parallel heater voltage
1.4 V
Parallel heater current
200 mA
Series capable
Yes

7B8 - 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
Plate resistance
90000 Ω
Transconductance
0.0019 S
Amplification factor
190
Max plate voltage
150 V
Max screen voltage
135 V
Max plate dissipation
2 W
Max screen dissipation
0.9 W
Max grid dissipation
0.00025 W
Max cathode current
25 mA

Promoted maximum values include the most permissive published AF/RF rating where applicable.

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 RCA Transmitting Tubes

Published operating points and test conditions from this source.

SECTION 1

Pentode

Other

  • Maximum Plate/Inverse Voltage

    135 V

    Source rating

  • Maximum Plate Dissipation

    1.5 W

Characteristics

  • Parallel Filament Voltage

    1.4 V

  • Parallel Filament Current

    220 mA

Data set 02

195X General Electric Essential Characteristics

Published operating points and test conditions from this source.

SECTION 1

Pentode

Other

  • Maximum plate voltage

    150 V

    Published handbook rating

  • Maximum screen voltage

    90 V

    Published handbook rating

  • Plate voltage

    150 V

    ClassA

  • Screen voltage

    90 V

    ClassA

  • Control-grid bias

    8.4 V

    ClassA

  • Plate current

    13.3 mA

    ClassA

  • Screen current

    2.2 mA

    ClassA

  • Load resistance

    8000 ohm

    ClassA

  • Power output

    0.7 W

    ClassA

Characteristic

  • Plate resistance

    100000 ohm

    Published handbook characteristic

  • Transconductance

    1900 µS

    Published handbook characteristic

  • Heater/filament voltage

    2.8 V

    Published heater/filament rating

  • Heater/filament current

    100 mA

    Published heater/filament rating

Data set 03

195X Raytheon Special Purpose Tubes

Published operating points and test conditions from this source.

SECTION 1

Pentode

Other

  • Plate Voltage

    150 V

  • Grid 1 Voltage

    -8.4 V

  • Grid 2 Voltage

    90 V

  • Plate Current

    13.3 mA

  • Grid 2 Current

    2.2 mA

  • Output Power

    0.7 W

  • Load Resistance

    8000 ohm

Characteristic

  • Plate Resistance

    0.1 Mohm

  • Transconductance

    1900 uS

Data set 04

1960 RCA Industrial and Communications Types

Published operating points and test conditions from this source.

SECTION 1

Pentode

Other

  • RF power output at 10 MHz

    1.2 W

    ClassC

Data set 05

1961 Tung Sol

Published operating points and test conditions from this source.

SECTION 1

Pentode

Other

  • Plate voltage

    150 V

    AFPowerAmplifier

  • Screen voltage

    90 V

    AFPowerAmplifier

  • Plate dissipation

    2 W

  • Screen dissipation

    0.9 W

    RFPowerAmplifier

  • Plate voltage

    150 V

    ClassA

  • Load resistance

    8000 ohm

    ClassA

  • Maximum-signal power output

    0.7 W

    ClassA

  • RF power output

    1.2 W

    10MHz

Data set 06

1966 Tung Sol Electronic Tubes 1 of 4

Published operating points and test conditions from this source.

SECTION 1

Pentode

Characteristic

  • FIER SERVICE THE

    1.2 W

    | FIER SERVICE THE 3A4 WILL DELIVER A POWER OUTPUT OF ABOUT 1.2 WATTS AT

  • PLATE VOLTAGE

    150 V

    ClassA | PLATE VOLTAGE 135 150 150 VOLTS

  • SCREEN VOLTAGE

    135 V

    ClassA | SCREEN VOLTAGE 9O 9O 135 VOLTS

  • PEAK AF GRID VOLTAGE

    4 V

    ClassA | PEAK AF GRID VOLTAGE 7.5 $.4 VOLTS

  • ZERO-SIGNAL PLATE CURRENT

    13.3 mA

    ClassA | ZERO-SIGNAL PLATE CURRENT 14.$ 13.3 MA.

  • MA%IMU M-SIGNAL PLATE CURRENT

    3 mA

    ClassA | MA%IMU M-SIGNAL PLATE CURRENT 14.9 14.1 1$.3 MA.

  • GRID CURRENT

    0.13 mA

    ClassA | GRID CURRENT --- --- 0.13 MA.

  • Filament voltage

    2.8 V

    SeriesFilament

  • Filament current

    100 mA

    SeriesFilament

  • Filament voltage

    1.4 V

    ParallelFilament

  • Filament current

    200 mA

    ParallelFilament

Other

  • MAXIMUM PLATE VOI TA GE

    150 V

    | MAXIMUM PLATE VOI TA GE 150 150 voLTs

  • MAXIMUM SCREEN VOLTAGE

    135 V

    | MAXIMUM SCREEN VOLTAGE 90 135 voLTs

  • MAXIMUM GRID VOLTAGE

    -30 V

    | MAXIMUM GRID VOLTAGE --- -30 voLTs

  • MAXIMUM PLATE CUrtRENT

    20 mA

    | MAXIMUM PLATE CUrtRENT 20 Ma.

  • MAXIMUM GRID CURRENT

    0.25 mA

    | MAXIMUM GRID CURRENT --- 0.25 Ma.

  • MAXIMUM TOTAL CATNODE CURRENT

    25 mA

    | MAXIMUM TOTAL CATNODE CURRENT 18 25 MA.

  • MAXIMUM SCREEN DISSIPATION O

    9 W

    | MAXIMUM SCREEN DISSIPATION O.4 O.9 WATT

  • MAXIMUM-SIGNAL SCREEN CURRENT

    6.5 mA

    ClassA | MAXIMUM-SIGNAL SCREEN CURRENT 3.5 3.5 6.5 MA.

  • MAXIMUM-SIGNAL POWER OUTPUT O

    1 W

    ClassA | MAXIMUM-SIGNAL POWER OUTPUT O.6 O.~ 1.ZIAPPRO%. 1 WATTS

Data set 07

1968 Mazda Belvu

Published operating points and test conditions from this source.

SECTION 1

Pentode

Characteristics

  • Heater or filament voltage

    1.4 V

    Published nominal value

  • Heater or filament current

    200 mA

    Published nominal value

  • Transconductance

    1900 µS

    Published operating characteristic

Other

  • Maximum plate dissipation

    2.2 W

    Published maximum rating

  • Audio output power

    0.7 W

    ClassA; 150 V plate condition

Data set 08

1971 RCA HB3 Binder 3 of 7

Published operating points and test conditions from this source.

SECTION 1

Pentode

Other

  • Maximum plate voltage

    - to 150 V

  • Maximum screen voltage

    - to 135 V

  • Maximum plate dissipation

    - to 2 W

  • Maximum screen dissipation

    - to 0.9 W

  • Maximum cathode current

    - to 25 mA

  • AF plate voltage

    135 V

    ClassA

  • AF plate voltage

    150 V

    ClassA

  • AF screen voltage

    90 V

    ClassA

  • AF grid voltage

    -7.5 V

    ClassA

  • AF grid voltage

    -8.4 V

    ClassA

  • Zero-signal plate current

    14.8 mA

    ClassA

  • Zero-signal plate current

    13.3 mA

    ClassA

  • Zero-signal screen current

    2.6 mA

    ClassA

  • Load resistance

    8000 Ω

    ClassA

  • Maximum-signal power output

    700 mW

    ClassA

  • RF plate voltage

    150 V

    ClassC

  • RF screen voltage

    135 V

    ClassC

  • RF plate current

    18.3 mA

    ClassC

  • RF power output

    1.2 W

    ClassC

Characteristics

  • Plate resistance

    100000 Ω

  • Transconductance

    1900 µS

Capacitance

  • Grid to Plate

    0.34 pF

  • Input

    4.8 pF

  • Output

    4.2 pF