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Voltage - Dual Triode (similar) ·Triode-Triode

7F7

High-mu dual triode designed for resistance-coupled cascade voltage amplification and phase-inverter service, combining two voltage-amplifier sections in a Loctal envelope.

Directly heatedCold cathodeCommon cathodeDissimilar
Sections
2
Base
8AC
Socket code
B8G
Base pins
8
Nominal heater
6.3 V / 300 mA

Description

The 7F7 combines two high-mu triodes for resistance-coupled cascade voltage amplification or phase-inverter service.

Socket description

Loctal 8-contact

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base
8AC
Socket code
B8G
Base pins
8
Nominal heater voltage
6.3 V
Nominal heater current
300 mA
Parallel heater voltage
-
Parallel heater current
-
Series capable
No

8AC - Terminal pinout

Electrical assignments shared by every tube using this base designation.

No verified pinout is recorded for this base designation.

Section ratings

2 physical sections, each with unique specifications.

Section 1

Triode

X-ray radiationInterelectrode capacitances
Plate resistance
44000 Ω
Transconductance
0.0016 S
Amplification factor
70
Max plate voltage
300 V
Max plate dissipation
1 W

Published promoted fields populated by semantic heading; identical repeated physical sections compressed.

Section 2

Triode

X-ray radiationInterelectrode capacitances
Plate resistance
44000 Ω
Transconductance
0.0016 S
Amplification factor
70
Max plate voltage
300 V
Max plate dissipation
1 W

Second physical triode section; added to align rows with SectionCount.

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

1948 Brimar Radio Valve Manual

Published operating points and test conditions from this source.

SECTION 1

Triode

Other

  • Plate Voltage

    250 V

    EachSection

  • Plate Current

    2.3 mA

    EachSection

  • Control Grid Voltage

    -2 V

    EachSection

Characteristic

  • Plate Resistance

    44000 ohm

    EachSection

  • Transconductance

    1600 µS

    EachSection

  • Amplification Factor

    70

    EachSection

Data set 02

1950 Sylvania

Published operating points and test conditions from this source.

SECTION 1

Triode

Other

  • HeaterVoltageNominal

    7 V

    Nominal

  • HeaterCurrentNominal

    320 mA

    Nominal

  • Plate Voltage

    250 V

    ClassA

Data set 03

195X General Electric Essential Characteristics

Published operating points and test conditions from this source.

SECTION 1

Triode

Other

  • Typical plate voltage

    250 V

    ClassA;EachSection

  • Typical grid voltage

    -2 V

    ClassA;EachSection

  • Typical plate current

    2.3 mA

    ClassA;EachSection

Characteristic

  • Plate resistance

    44000 Ohm

    EachSection

  • Transconductance

    1600 uS

    EachSection

  • Amplification factor

    70

    EachSection

Data set 04

1961 Tung Sol

Published operating points and test conditions from this source.

SECTION 1

Triode

Characteristic

  • Plate Resistance

    62000 ohm

    AlternateOperatingPoint

  • Transconductance

    1125 uS

    AlternateOperatingPoint

Data set 05

1966 Tung Sol Electronic Tubes 2 of 4

Published operating points and test conditions from this source.

SECTION 1

Triode

Other

  • Plate_voltage

    250 V

    Section1,Section2,ClassA

Characteristic

  • Plate_current

    2.3 mA

    Section1,Section2,ClassA

  • Plate_resistance

    44000 ohm

    Section1,Section2,ClassA

  • Amplification_factor

    70

    Section1,Section2,ClassA

  • Transconductance

    1600 uS

    Section1,Section2,ClassA

Capacitance

  • Grid-to-plate capacitance

    1.6 pF

    Section1,Section2

  • Input capacitance

    3 pF

    Section1,Section2

  • Output capacitance

    0.4 pF

    Section1,Section2