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Power - Triode Single (under 10W) ·Triode-Triode

3A5

Directly heated high-frequency twin triode intended for portable or battery equipment, usable as an RF amplifier or oscillator and capable of about 2 W push-pull Class-C RF output at 40 MHz.

Directly heatedCold cathodeCommon cathodeDissimilar

Sections: 2
Base: 7BC
Socket code: B7G
Base pins: 7
Nominal heater: 2.8 V / 110 mA

Description

3A5 is a DualTriode vacuum tube documented in the RCA Receiving Tube Manual. The supplied excerpt was reviewed for heater or filament data, physical section arrangement, maximum ratings, electrical characteristics, capacitances, and stated application.

Socket description

Miniature 7-contact

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base: 7BC
Socket code: B7G
Base pins: 7
Nominal heater voltage: 2.8 V
Nominal heater current: 110 mA
Parallel heater voltage: 1.4 V
Parallel heater current: 220 mA
Series capable: Yes

7BC - Terminal pinout

Electrical assignments shared by every tube using this base designation.

Terminal	Section	Connection	Evidence
PIN1F	—	F — Filament EIA transcription; manufacturer confirmation pending	Unverified EIA Base Connections, printed page 128, 7BC
PIN22P	B	P — Plate (Anode) EIA transcription; manufacturer confirmation pending	Unverified EIA Base Connections, printed page 128, 7BC
PIN32G1	B	G1 — Control Grid EIA transcription; manufacturer confirmation pending	Unverified EIA Base Connections, printed page 128, 7BC
PIN4FCT	—	FCT — Filament Center Tap EIA transcription; manufacturer confirmation pending	Unverified EIA Base Connections, printed page 128, 7BC
PIN51G1	A	G1 — Control Grid EIA transcription; manufacturer confirmation pending	Unverified EIA Base Connections, printed page 128, 7BC
PIN61P	A	P — Plate (Anode) EIA transcription; manufacturer confirmation pending	Unverified EIA Base Connections, printed page 128, 7BC
PIN7F	—	F — Filament EIA transcription; manufacturer confirmation pending	Unverified EIA Base Connections, printed page 128, 7BC

Section ratings

2 physical sections, each with unique specifications.

Section 1

Triode

X-ray radiationInterelectrode capacitances

Plate resistance: 8300 Ω
Transconductance: 0.0018 S
Amplification factor: 15
Max plate voltage: 135 V
Max plate dissipation: 1 W
Max grid dissipation: 0.0025 W
Max cathode current: 15 mA

Representative row for two electrically identical triode units; RF per-unit dissipation/current ratings promoted.

Section 2

Triode

X-ray radiationInterelectrode capacitances

Plate resistance: 8300 Ω
Transconductance: 0.0018 S
Amplification factor: 15
Max plate voltage: 135 V
Max plate dissipation: 1 W
Max cathode current: 15 mA

Second physical triode restored under current one-row-per-physical-section policy.

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

1956 RCA Transmitting Tubes

Published operating points and test conditions from this source.

SECTION 1

Triode

Other

Maximum Plate/Inverse Voltage
135 V
Source rating
Maximum Plate Dissipation
1 W

Characteristics

Parallel Filament Voltage
1.4 V
Parallel Filament Current
220 mA

Data set 02

195X General Electric Essential Characteristics

Published operating points and test conditions from this source.

SECTION 1

Triode

Other

Maximum plate voltage
135 V
Published handbook rating
Plate voltage
90 V
ClassA
Control-grid bias
2.5 V
ClassA
Plate current
3.7 mA
ClassA

Characteristic

Plate resistance
8300 ohm
Published handbook characteristic
Transconductance
1800 µS
Published handbook characteristic
Amplification factor
15
Published handbook characteristic
Heater/filament voltage
2.8 V
Published heater/filament rating
Heater/filament current
110 mA
Published heater/filament rating

Data set 03

195X Raytheon Special Purpose Tubes

Published operating points and test conditions from this source.

SECTION 1

Triode

Other

Plate Voltage
90 V
Grid 1 Voltage
-2.5 V
Plate Current
3.7 mA

Characteristic

Transconductance
1800 uS
Amplification Factor
15

Data set 04

1960 RCA Industrial and Communications Types

Published operating points and test conditions from this source.

SECTION 1

Triode

Other

Push-pull RF output at 40 MHz
2 W
ClassC,PushPull
Driving power at 40 MHz
0.2 W
ClassC,PushPull

Data set 05

1961 Tung Sol

Published operating points and test conditions from this source.

SECTION 1

Triode

Other

Plate voltage
135 V
Plate dissipation per unit
1 W
RFAmplifier
DC plate current per unit
15 mA
RFAmplifier
RF power output
2 W
PushPull;ClassC;40MHz

Characteristic

Plate resistance
8300 ohm
Transconductance
1800 uS

Data set 06

1966 Tung Sol Electronic Tubes 1 of 4

Published operating points and test conditions from this source.

SECTION 1

Triode

Capacitance

GRID TO PLATE: (G TO P)
3.2 ΜΜF
Capacitances | GRID TO PLATE: (G TO P) 3.2 3.2 µµf
PLATE TO PLATE: (P TO P)
0.32 ΜΜF
Capacitances | PLATE TO PLATE: (P TO P) 0.32 µµf

Other

FILAMENT VOLTAGE I
2.8 V
Maximum Ratings | FILAMENT VOLTAGE I.4 2.8 I.4 2.8 VOLTS
MAXIMUM PLATE VOLTAGE
135 V
Maximum Ratings | MAXIMUM PLATE VOLTAGE 135 135 VOLTS
MAXIMUM DC PLATE CURRENT (PEA UNIT) --- I
5 mA
Maximum Ratings | MAXIMUM DC PLATE CURRENT (PEA UNIT) --- I5 MA.
MAXIMUM DC GRID CURRENT (pER UNIT)
2.5 mA
Maximum Ratings | MAXIMUM DC GRID CURRENT (pER UNIT) --- 2.5 MA.
PLATE VOLTAGE
90 V
Typical Operating Conditions | PLATE VOLTAGE 90 VOLTS
GRID VOLTAGE -Z
5 V
Typical Operating Conditions | GRID VOLTAGE -Z.5 VOLTS
PLA iF CURRENT
3.7 mA
Typical Operating Conditions | PLA iF CURRENT 3.7 MA.
DC PLATE VOI TA GE
135 V
Oscillator | DC PLATE VOI TA GE 135 VOLTS
FROM A GRID RESISTOR OF
0 ohm
Oscillator | FROM A GRID RESISTOR OF 4 O00 OHMS
DC GRID CURRENT (APPR OX.)
5 mA
Oscillator | DC GRID CURRENT (APPR OX.) 5 MA.

Characteristic

Filament voltage
2.8 V
SeriesFilament
Filament current
110 mA
SeriesFilament
Filament voltage
1.4 V
ParallelFilament
Filament current
220 mA
ParallelFilament

Data set 07

1971 RCA HB3 Binder 3 of 7

Published operating points and test conditions from this source.

SECTION 1

Triode

Other

Maximum plate voltage
- to 135 V
Maximum plate dissipation
- to 1 W
Maximum cathode current
- to 15 mA
Push-pull plate voltage
135 V
PushPull
Push-pull grid voltage
-20 V
PushPull
Push-pull plate current
30 mA
PushPull
Driving power
0.2 W
PushPull
Power output
2 W
PushPull

Characteristics

Plate resistance
8300 Ω
Transconductance
1800 µS
Plate voltage
90 V
ClassA
Grid voltage
-2.5 V
ClassA
Amplification factor
15
ClassA
Plate resistance
8300 Ω
ClassA
Transconductance
1800 µS
ClassA
Plate current
3.7 mA
ClassA

Capacitance

Plate to Filament
1 to 1 pF

Data set 08

1975 RCA RC30

Published operating points and test conditions from this source.

SECTION 1

Triode

Other

Filament Voltage (de) 2.8
1.4 V
Filament Voltage (de) 2.8 1.4 volts
Filament Current 0.11
220 mA
Filament Current 0.11 0.22 ampere
Plate Voltage
135 V
Plate Voltage 135 volts
Plate Current
6 mA
Plate Current 6 mA
Plate Dissipation
0.5 W
Plate Dissipation 0.5 watt
DC Plate Voltage
135 V
DC Plate Voltage 135 volts
DC Plate Current (per unit)
15 mA
DC Plate Current (per unit) 15 mA
DC Grid Current (per unit)
2.5 mA
DC Grid Current (per unit) 2.5 mA
Plate Dissipation (per unit) 1
0 W
Plate Dissipation (per unit) 1-0 watt
DC Grid Voltage*
4000 ohm
DC Grid Voltage* 4000 ohms
Peak R-F Grid-to-Grid Voltage
90 V
Peak R-F Grid-to-Grid Voltage 90 volts
DC Plate Current
30 mA
DC Plate Current 30 mA
DC Grid Current (approx.)
5 mA
DC Grid Current (approx.) 5 mA
Maximum plate voltage
135 V
Published maximum rating
Maximum plate dissipation
0.5 W
Published maximum rating

Characteristic

Grid Voltage —
2.5 V
Grid Voltage —2.5 volts
Plate Resistance
8300 ohm
Plate Resistance 8300 ohms
Plate Current
3.7 mA
Plate Current 3.7 mA
Heater voltage
1.4 V
Rated heater/filament condition
Heater current
220 mA
Rated heater/filament condition
Amplification factor
15
Published section characteristic