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Voltage Triode Pentode ·Diode-Pentode-Triode

25D8GT

Diode-triode-pentode for compact AC/DC receivers, combining RF/IF amplification, detector, and audio-frequency signal functions.

Directly heatedCold cathodeCommon cathodeDissimilar
Sections
3
Base
8AF
Socket code
IO
Base pins
8
Nominal heater
25 V / 150 mA

Description

Midget diode-triode-pentode for small AC-DC receivers; the pentode can serve as an RF or IF amplifier and the diode-triode section as detector and AF amplifier.

Socket description

International Octal

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base
8AF
Socket code
IO
Base pins
8
Nominal heater voltage
25 V
Nominal heater current
150 mA
Parallel heater voltage
-
Parallel heater current
-
Series capable
No

8AF - 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

No fixed ratings are recorded for this section.

Detector-diode section is physically present; this source publishes no separate diode maximum-rating table.

Section 2

Triode

X-ray radiationInterelectrode capacitances
Plate resistance
91000 Ω
Transconductance
0.0011 S
Amplification factor
100
Max plate voltage
100 V

Published section data promoted where applicable; additional operating values retained as parameters.

Section 3

Pentode

X-ray radiationInterelectrode capacitances
Plate resistance
200000 Ω
Transconductance
0.0019 S
Max plate voltage
100 V
Max screen voltage
100 V

Published section data promoted where applicable; additional operating values retained as parameters.

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

1939 Arcturus

Published operating points and test conditions from this source.

SECTION 2

Triode

Other

  • Plate voltage

    100 V

  • Control-grid voltage

    -1 V

  • Plate current

    0.5 mA

SECTION 3

Pentode

Other

  • Plate voltage

    100 V

  • Screen-grid voltage

    100 V

  • Control-grid voltage

    -3 V

  • Plate current

    8.5 mA

  • Screen-grid current

    2.7 mA

Data set 02

195X General Electric Essential Characteristics

Published operating points and test conditions from this source.

SECTION 2

Triode

Other

  • Plate voltage

    100 V

    ClassA

  • Grid voltage

    -1 V

    ClassA

  • Plate current

    0.5 mA

    ClassA

SECTION 3

Pentode

Other

  • Plate voltage

    100 V

    ClassA

  • Screen-grid voltage

    100 V

    ClassA

  • Grid voltage

    -3 V

    ClassA

  • Plate current

    8.5 mA

    ClassA

  • Screen-grid current

    2.7 mA

    ClassA

Data set 03

1961 Tung Sol

Published operating points and test conditions from this source.

SECTION 1

Diode

Other

  • Heater voltage

    25 V

    Nominal

  • Heater current

    150 mA

    Nominal

SECTION 2

Triode

Other

  • Heater voltage

    25 V

    Nominal

  • Heater current

    150 mA

    Nominal

  • Plate voltage

    100 V

    ClassA

  • Grid voltage

    -1 V

    ClassA

Characteristic

  • Plate current

    0.5 mA

    ClassA

  • Plate resistance

    91000 ohm

    ClassA

  • Transconductance

    1100 uS

    ClassA

  • Amplification factor

    100

    ClassA

Capacitance

  • Control grid to cathode

    3.7 pF

    Direct interelectrode capacitance

  • Plate to cathode

    4.5 pF

    Direct interelectrode capacitance

  • Control grid to plate

    2.5 pF

    Direct interelectrode capacitance

SECTION 3

Pentode

Other

  • Heater voltage

    25 V

    Nominal

  • Heater current

    150 mA

    Nominal

  • Plate voltage

    100 V

    ClassA

  • Screen voltage

    100 V

    ClassA

  • Control-grid voltage

    -3 V

    ClassA

Characteristic

  • Plate current

    8.5 mA

    ClassA

  • Screen current

    2.7 mA

    ClassA

  • Plate resistance

    200000 ohm

    ClassA

  • Transconductance

    1900 uS

    ClassA

  • Control-grid voltage for transconductance 2 uS

    -35 V

    ClassA

Capacitance

  • Control grid to cathode

    5.2 pF

    Direct interelectrode capacitance

  • Plate to cathode

    10 pF

    Direct interelectrode capacitance

  • Control grid to plate

    0.015 pF

    Direct interelectrode capacitance

  • Pentode control grid to triode grid

    0.01 pF

    Cross-section capacitance

  • Pentode control grid to triode plate

    0.02 pF

    Cross-section capacitance

  • Pentode plate to triode grid

    0.1 pF

    Cross-section capacitance