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Rectifier - Full Wave ·Pentode-Rectifier

25A7G

Combination rectifier diode and power pentode designed to integrate receiver power-supply rectification with audio power-output amplification.

Directly heatedCold cathodeCommon cathodeDissimilar

Sections: 2
Base: -
Socket code: IO
Base pins: 8
Nominal heater: 25 V / 300 mA

Description

Combined rectifier diode and power pentode.

Socket description

International Octal

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base: -
Socket code: IO
Base pins: 8
Nominal heater voltage: 25 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

2 physical sections, each with unique specifications.

Section 1

Pentode

X-ray radiationInterelectrode capacitances

Plate resistance: 50000 Ω
Transconductance: 0.0018 S
Max plate voltage: 117 V
Max screen voltage: 117 V
Max plate dissipation: 2.25 W
Max screen dissipation: 0.8 W

Electrical section reconstructed from published ratings/characteristics; promoted transconductance normalized to A/V.

Section 2

Rectifier

X-ray radiationInterelectrode capacitances

Rectifier peak inverse voltage: 350 V
Rectifier nominal output current: 75 mA
Rectifier peak forward current: 450 mA

Physical section represented from published tube construction and section-specific data.

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
100 V
Published ratings
Maximum Screen Voltage
100 V
Published ratings
Plate Voltage
100 V
ClassA
Screen Voltage
100 V
ClassA
Grid Bias
-15 V
ClassA
Plate Resistance
30000 ohm
ClassA
Transconductance
1800
ClassA
Plate Current
20.5 mA
ClassA
Load Resistance
4500 ohm
ClassA
Total Harmonic Distortion
9 %
ClassA
Power Output
0.77 W
ClassA
Maximum A-C Plate Voltage RMS
125 V
ClassA
Maximum D-C Output Current
75 mA
ClassA

Data set 02

1948 Brimar Radio Valve Manual

Published operating points and test conditions from this source.

SECTION 1

Pentode

Other

Power Output
0.77 W
PentodeSection

SECTION 2

Rectifier

Characteristic

HeaterOrFilamentVoltage
25 V
HeaterOrFilamentCurrent
300 mA

Other

RMSInput
125 V
RectifierSection

Data set 03

1961 Tung Sol

Published operating points and test conditions from this source.

SECTION 1

Pentode

Other

Plate Voltage
100 V
ClassA
Screen Voltage
100 V
ClassA
Power Output
0.77 W
ClassA

SECTION 2

Rectifier

Other

Maximum AC Plate Voltage RMS
117 V
Minimum Effective Plate Supply Impedance
15 ohm

Characteristic

Tube Voltage Drop
23 V
PlateCurrent=150mA