3B7

Directly heated high-frequency twin triode for low-voltage battery operation, providing two triode units suitable for amplification and push-pull service in portable radio-frequency equipment.

Directly heatedCold cathodeCommon cathodeDissimilar

Sections: 2
Base: 7BE
Socket code: OCTAL7
Base pins: 8
Nominal heater: 2.8 V / 220 mA

Description

3B7 is listed in the supplied receiving-tube handbook as a high-frequency twin triode. The published heater/filament rating is 1.4 V at 0.22 A.

Socket description

7-contact octal-family base

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base: 7BE
Socket code: OCTAL7
Base pins: 8
Nominal heater voltage: 2.8 V
Nominal heater current: 220 mA
Parallel heater voltage: 1.4 V
Parallel heater current: 440 mA
Series capable: Yes

7BE - 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: 100000 Ω
Transconductance: 0.0015 S
Amplification factor: 20
Max plate voltage: 180 V
Max cathode current: 15 mA

Published ratings/characteristics promoted where semantically applicable; supplemental values retained in parameter table.

Section 2

Triode

X-ray radiationInterelectrode capacitances

Plate resistance: 100000 Ω
Transconductance: 0.0015 S
Amplification factor: 20
Max plate voltage: 180 V
Max cathode current: 15 mA

Second identical 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

195X General Electric Essential Characteristics

Published operating points and test conditions from this source.

SECTION 1

Triode

Other

Maximum plate voltage
180 V
Published handbook rating
Plate voltage
135 V
ClassAB PushPull TwoTubes
Control-grid bias
0 V
ClassA
Plate current
18.2 mA
ClassA
Load resistance
16000 ohm
ClassAB PushPull TwoTubes
Power output
1.5 W
ClassAB PushPull TwoTubes

Characteristic

Transconductance
1900 µS
Published handbook characteristic
Amplification factor
20
Published handbook characteristic
Heater/filament voltage
1.4 V
Published heater/filament rating
Heater/filament current
220 mA
Published heater/filament rating

Data set 02

1961 Tung Sol

Published operating points and test conditions from this source.

SECTION 1

Triode

Other

Heater Voltage Series
2.8 V
SeriesFilaments
Heater Voltage Parallel
1.4 V
ParallelFilaments