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Voltage - Triode (with diode, heptode or hexode) ·Diode-Diode-Triode

7K7

Double-diode triode combining radio detector and AVC rectification with subsequent voltage amplification. The paired diodes handle signal and control-voltage functions while the triode provides receiver audio or voltage gain.

Directly heatedCold cathodeCommon cathodeDissimilar
Sections
3
Base
-
Socket code
B8G
Base pins
8
Nominal heater
6.3 V / 300 mA

Description

A duodiode high-mu triode with separate diode and triode cathodes for greater circuit flexibility.

Socket description

Loctal 8-contact

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base
-
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

Terminal pinout

Electrical assignments shared by every tube using this base designation.

No verified pinout is recorded for this base designation.

Section ratings

3 physical sections, each with unique specifications.

Section 1

Diode

X-ray radiationInterelectrode capacitances
Rectifier max heater-cathode voltage
90 V

Published promoted fields populated by semantic section ownership; identical repeated 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
Rectifier max heater-cathode voltage
90 V

Published promoted fields populated by semantic section ownership; identical repeated sections compressed.

Section 3

Diode

X-ray radiationInterelectrode capacitances

No fixed ratings are recorded for this section.

Physical diode section added during approved section-structure reconciliation.

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 2

Triode

Other

  • Plate Voltage

    250 V

    TriodeSection

  • Plate Current

    2.3 mA

    TriodeSection

  • Control Grid Voltage

    -2 V

    TriodeSection

  • Cathode Bias Resistor

    1000 ohm

    TriodeSection

Characteristic

  • Plate Resistance

    44000 ohm

    TriodeSection

  • Transconductance

    1600 µS

    TriodeSection

  • Amplification Factor

    70

    TriodeSection

Data set 02

1950 Sylvania

Published operating points and test conditions from this source.

SECTION 2

Triode

Other

  • HeaterVoltageNominal

    7 V

    Nominal

  • HeaterCurrentNominal

    320 mA

    Nominal

  • Plate Voltage

    250 V

    ClassA

Data set 03

1961 Ferranti Technical Handbook

Published operating points and test conditions from this source.

SECTION 2

Triode

Other

  • Plate Voltage

    250 V

    ClassA

  • Grid Voltage

    -2 V

    ClassA

  • Plate Current

    2.3 mA

    ClassA

Characteristics

  • Transconductance

    1600 uS

  • Plate Resistance

    44000 ohm

  • Amplification Factor

    70 ratio

Data set 04

1961 Tung Sol

Published operating points and test conditions from this source.

SECTION 1

Diode

Capacitance

  • Grid To Plate Capacitance

    1.7 pF

    Triode

SECTION 2

Triode

Characteristic

  • TriodePlateResistance

    44000 ohm

    Section2

  • TriodeTransconductance

    1600 uS

    Section2