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Voltage Radio Detector Converter ·Diode-Diode-Pentode

7R7

Double-diode semi-variable-mu pentode for radio detector plus IF/LF amplifier service. The paired diodes provide detection and AVC while the controlled-cutoff pentode supports gain-regulated receiver amplification.

Directly heatedCold cathodeCommon cathodeDissimilar

Sections: 3
Base: -
Socket code: B8G
Base pins: 8
Nominal heater: 6.3 V / 300 mA

Description

Double-diode RF pentode for detector plus IF/LF amplifier service; the pentode section has semi-variable-mu characteristics for AVC.

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

Pentode

X-ray radiationInterelectrode capacitances

Plate resistance: 1000000 Ω
Transconductance: 0.0034 S
Max plate voltage: 300 V
Max screen voltage: 150 V
Max plate dissipation: 2 W
Max screen dissipation: 0.7 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

Pentode

Other

Plate Voltage
250 V
PentodeSection
Plate Current
5.7 mA
PentodeSection
Screen Voltage
100 V
PentodeSection
Screen Current
1.7 mA
PentodeSection
Control Grid Voltage
-1 V
PentodeSection

Characteristic

Plate Resistance
1 Mohm
PentodeSection
Transconductance
3200 µS
PentodeSection
Cutoff Grid Voltage
-20 V
PentodeSection

Data set 02

1958 Brimar Radio Valve No 7

Published operating points and test conditions from this source.

SECTION 2

Pentode

Characteristics

Cutoff characteristic
Semi-vari-mu

Data set 03

1961 Tung Sol

Published operating points and test conditions from this source.

SECTION 2

Pentode

Characteristic

PentodeTransconductance
3400 uS
Section2
PentodePlateResistance
1000000 ohm
Section2