25B6G

Power/output pentode designed for Class-A, single-ended, or push-pull audio-frequency output amplification.

Directly heatedCold cathodeCommon cathodeDissimilar

Sections: 1
Base: 7S
Socket code: IO
Base pins: 7
Nominal heater: 25 V / 300 mA

Description

Power pentode for low-voltage audio output service.

Socket description

International Octal

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base: 7S
Socket code: IO
Base pins: 7
Nominal heater voltage: 25 V
Nominal heater current: 300 mA
Parallel heater voltage: -
Parallel heater current: -
Series capable: No

7S - Terminal pinout

Electrical assignments shared by every tube using this base designation.

Terminal	Section	Connection	Evidence
PIN1IS	A	IS — Internal Screen EIA chart transcription; independent manufacturer verification pending	Unverified EIA Base Connections, printed page 128, 7S
PIN2H	—	H — Heater EIA chart transcription; independent manufacturer verification pending	Unverified EIA Base Connections, printed page 128, 7S
PIN3P	A	P — Plate (Anode) EIA chart transcription; independent manufacturer verification pending	Unverified EIA Base Connections, printed page 128, 7S
PIN4G2	A	G2 — Screen Grid EIA chart transcription; independent manufacturer verification pending	Unverified EIA Base Connections, printed page 128, 7S
PIN5G1	A	G1 — Control Grid EIA chart transcription; independent manufacturer verification pending	Unverified EIA Base Connections, printed page 128, 7S
PIN7H	—	H — Heater EIA chart transcription; independent manufacturer verification pending	Unverified EIA Base Connections, printed page 128, 7S
PIN8G3	A	G3 — Suppressor GridGroup 7S8 EIA chart transcription; independent manufacturer verification pending	Unverified EIA Base Connections, printed page 128, 7S
PIN8K	A	K — CathodeGroup 7S8 EIA chart transcription; independent manufacturer verification pending	Unverified EIA Base Connections, printed page 128, 7S

Section ratings

1 physical section, each with unique specifications.

Section 1

Pentode

X-ray radiationInterelectrode capacitances

Plate resistance: 18000 Ω
Transconductance: 0.005 S
Max plate voltage: 200 V
Max screen voltage: 135 V
Max plate dissipation: 12.5 W
Max screen dissipation: 2 W

Power-amplifier pentode section.

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

1937 Raytheon Radio Receiving Tubes

Published operating points and test conditions from this source.

SECTION 1

Pentode

Other

Maximum Plate Voltage
96 V
Published ratings
Maximum Screen Voltage
95 V
Published ratings
Plate Voltage
95 V
ClassA
Screen Voltage
85 V
ClassA
Transconductance
4000
ClassA
Plate Current
45 mA
ClassA
Screen Current
4 mA
ClassA
Load Resistance
2000 ohm
ClassA
Total Harmonics
10 %
ClassA
Power Output
1.78 W
ClassA

Data set 02

1950 Sylvania

Published operating points and test conditions from this source.

SECTION 1

Pentode

Application

Service
Audio power output

Data set 03

195X General Electric Essential Characteristics

Published operating points and test conditions from this source.

SECTION 1

Pentode

Other

Plate voltage
200 V
ClassA
Screen-grid voltage
135 V
ClassA
Grid voltage
-23 V
ClassA
Plate current
62 mA
ClassA
Screen-grid current
1.8 mA
ClassA
Load resistance
2500 ohm
ClassA
Power output
7.1 W
ClassA

Data set 04

1961 Tung Sol

Published operating points and test conditions from this source.

SECTION 1

Pentode

Other

Heater voltage
25 V
Nominal
Heater current
300 mA
Nominal
Plate voltage
105 V
ClassA; OperatingPoint1
Plate voltage
135 V
ClassA; OperatingPoint2
Plate voltage
200 V
ClassA; OperatingPoint3
Screen voltage
105 V
ClassA; OperatingPoint1
Screen voltage
135 V
ClassA; OperatingPoint2
Screen voltage
135 V
ClassA; OperatingPoint3
Control-grid voltage
-16 V
ClassA; OperatingPoint1
Control-grid voltage
-22 V
ClassA; OperatingPoint2
Control-grid voltage
-23 V
ClassA; OperatingPoint3
Load resistance
1700 ohm
ClassA; OperatingPoint1
Load resistance
1700 ohm
ClassA; OperatingPoint2
Load resistance
2500 ohm
ClassA; OperatingPoint3
Total harmonic distortion
12.5 %
ClassA; OperatingPoint1
Total harmonic distortion
14 %
ClassA; OperatingPoint2
Total harmonic distortion
15 %
ClassA; OperatingPoint3
Power output
2.4 W
ClassA; OperatingPoint1
Power output
4.3 W
ClassA; OperatingPoint2
Power output
7.1 W
ClassA; OperatingPoint3

Characteristic

Zero-signal plate current
48 mA
ClassA; OperatingPoint1
Zero-signal plate current
61 mA
ClassA; OperatingPoint2
Zero-signal plate current
62 mA
ClassA; OperatingPoint3
Zero-signal screen current
2 mA
ClassA; OperatingPoint1
Zero-signal screen current
2.5 mA
ClassA; OperatingPoint2
Zero-signal screen current
1.8 mA
ClassA; OperatingPoint3
Plate resistance
15500 ohm
ClassA; OperatingPoint1
Plate resistance
15000 ohm
ClassA; OperatingPoint2
Plate resistance
18000 ohm
ClassA; OperatingPoint3
Transconductance
4800 uS
ClassA; OperatingPoint1
Transconductance
5000 uS
ClassA; OperatingPoint2
Transconductance
5000 uS
ClassA; OperatingPoint3