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

Voltage Radio Detector Converter ·Octode

7A8

Receiver oscillator-converter combining local oscillation and signal mixing for superheterodyne frequency conversion. Its multi-grid structure integrates the front-end frequency-changing functions in one envelope.

Directly heatedCold cathodeCommon cathodeDissimilar
Sections
1
Base
8U
Socket code
B8G
Base pins
8
Nominal heater
6.3 V / 320 mA

Description

Octode converter using lock-in construction for combined oscillator and mixer 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
8U
Socket code
B8G
Base pins
8
Nominal heater voltage
6.3 V
Nominal heater current
320 mA
Parallel heater voltage
-
Parallel heater current
-
Series capable
No

8U - 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

Octode

X-ray radiationInterelectrode capacitances
Plate resistance
700000 Ω
Transconductance
0.00055 S
Max plate voltage
250 V
Max screen voltage
100 V
Max plate dissipation
1 W
Max screen dissipation
0.3 W
Max grid dissipation
0.75 W
Max cathode current
13 mA

Published handbook ratings and representative operating characteristics reviewed.

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

Octode

Characteristics

  • Anode Voltage

    250 V

  • Anode Current

    3 mA

  • Screen Voltage

    100 V

  • Screen Current

    2.8 mA

  • Oscillator Anode Supply Voltage

    250 V

    G2

  • Oscillator Anode Resistor

    20000 ohm

  • Control Grid Voltage

    -3 V

    G4

  • Cathode Bias Resistor

    300 ohm

  • Oscillator Grid Resistor

    50000 ohm

    G1

  • Oscillator Grid Current

    0.4 mA

  • Conversion Conductance

    550 uS

Data set 02

1950 Sylvania

Published operating points and test conditions from this source.

SECTION 1

Octode

Other

  • Heater Voltage

    7 V

    Nominal published value

  • Heater Current

    160 mA

    Nominal published value

Data set 03

195X General Electric Essential Characteristics

Published operating points and test conditions from this source.

SECTION 1

Octode

Other

  • Maximum plate voltage

    300 V

    Published handbook rating

  • Maximum screen voltage

    100 V

    Published handbook rating

  • Plate voltage

    250 V

    ClassA

  • Screen voltage

    100 V

    ClassA

  • Control-grid bias

    3 V

    ClassA

  • Plate current

    3 mA

    ClassA

  • Screen current

    3.2 mA

    ClassA

Characteristic

  • Plate resistance

    700000 ohm

    Published handbook characteristic

  • Transconductance

    550 µS

    Published handbook characteristic

  • Heater voltage

    6.3 V

    Published heater rating

  • Heater current

    150 mA

    Published heater rating

Data set 04

1961 Tung Sol

Published operating points and test conditions from this source.

SECTION 1

Octode

Other

  • Heater voltage

    6.3 V

    Nominal

  • Heater current

    320 mA

    Nominal

  • Plate voltage

    100250 V

    Typical operating conditions

  • Screen voltage

    100 V

    Typical operating conditions

  • Plate current

    1.83.0 mA

    Typical operating conditions

  • Screen current

    2.73.2 mA

    Typical operating conditions

Data set 05

1966 Tung Sol Electronic Tubes 2 of 4

Published operating points and test conditions from this source.

SECTION 1

Octode

Capacitance

  • Mixer-grid to oscillator-anode capacitance

    0.3 pF

  • Mixer-grid to oscillator-grid capacitance

    0.15 pF

  • Oscillator-grid to oscillator-anode capacitance

    0.6 pF

  • Mixer input capacitance

    7.5 pF

  • Mixer output capacitance

    9 pF

  • Oscillator input capacitance

    3.8 pF

  • Oscillator output capacitance

    3.4 pF

Other

  • Plate voltage

    250 V

    Converter

  • Grids #3 and #5 voltage

    200 V

    Converter

  • Grid #2 voltage

    250 V

    Converter

  • Grid #4 voltage

    -3 V

    Converter

  • Plate current

    3 mA

    Converter

  • Total cathode current

    10.5 mA

    Converter

Characteristic

  • Plate resistance

    700000 ohm

    Converter

  • Conversion transconductance

    550 uS

    Converter

  • Oscillator transconductance grid #1 to grid #2

    1600 uS

    Oscillator

  • Oscillator amplification factor

    65

    Oscillator