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Power - Triode ·Triode

205D

Directly heated power triode intended for audio-frequency amplifier service. Manufacturer data emphasize power-output operation and the electrical characteristics of a low-mu filamentary triode rather than small-signal receiving use.

Directly heatedCold cathodeCommon cathodeDissimilar
Sections
1
Base
-
Socket code
MEDIUM4BAYONET
Base pins
4
Nominal heater
4.5 V / 1.6 A

Description

Transmitting/power triode for RF amplification, oscillation, modulation, and audio output.

Socket description

Medium 4-contact bayonet base

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base
-
Socket code
MEDIUM4BAYONET
Base pins
4
Nominal heater voltage
4.5 V
Nominal heater current
1.6 A
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

1 physical section, each with unique specifications.

Section 1

Triode

X-ray radiationInterelectrode capacitances
Plate resistance
4000 Ω
Amplification factor
7.3
Max plate voltage
400 V
Max plate dissipation
14 W
Max cathode current
50 mA

Promoted fields mapped from published ratings/characteristics; additional published values preserved in parameter table.

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

1933 Western Electric Tubes

Published operating points and test conditions from this source.

SECTION 1

Triode

Other

  • Plate-grid capacitance

    4.8 pF

    Published direct interelectrode capacitance

  • Plate-filament capacitance

    3 pF

    Published direct interelectrode capacitance

  • Grid-filament capacitance

    5.2 pF

    Published direct interelectrode capacitance

Data set 02

2026 Western Electric 200s

Published operating points and test conditions from this source.

SECTION 1

Triode

Characteristic

  • Filament Voltage

    4.5 Volt

    Filament Voltage 4.5 Volts, AC or DC

  • Filament Current

    1.6 Amperes

    Filament Current 1.6 Amperes

  • Average A m p l i fi c a t i o n Factor

    7.3

    Average A m p l i fi c a t i o n Factor 7.3

  • Ma.ximum Plate Voltage

    400 Volt

    Ma.ximum Plate Voltage 400 Volts

  • No

    205

    No. 205D Tube the second harmonic output, in the push-pull circuit, is reduced to the general

  • level of the third harmonic output. With a plate voltage of

    375 volt

    level of the third harmonic output. With a plate voltage of 375 volts, and a total plate current of

  • approximately

    42 milliamperes

    approximately 42 milliamperes, two No. 205D Tubes will give 2.4 watts output with a total

  • harmonic content of the order of

    1

    harmonic content of the order of 1.0 per cent.

  • Peak Power Output

    12 Watts

    Peak Power Output 12 Watts

  • The No

    205

    The No. 205D Tube will operate satisfactorily at or above 30,000 kilocycles if the radio-

  • Audio-frequency amplifier or modulator where power outputs of approximately

    1 watt

    Audio-frequency amplifier or modulator where power outputs of approximately 1 watt or less

  • Filament voltage

    4.5 volt

    Filament voltage 4.5 volts, a.c. or d.c.

  • Nominal fi l a m e n t current

    1.6 amperes

    Nominal fi l a m e n t current 1.6 amperes

  • Microphonic Noise—With a plate voltage of

    350 volt

    Microphonic Noise—With a plate voltage of 350 volts, a grid bias of —22.5 volts, and a load

  • resistance of

    100000 ohms

    resistance of 100,000 ohms, the mean microphonic noise output level of the 205D tube measured

  • M a x i m u m direct plate voltage

    400 volt

    M a x i m u m direct plate voltage 400 400 400 350 volts

  • M a x i m u m direct plate current

    50 milliamperes

    M a x i m u m direct plate current 50 35 50 40 milliamperes

  • M a x i m u m direct grid current

    10 milliamperes

    M a x i m u m direct grid current 10 10 10 milliamperes

  • ♦Carrier conditions for use with modulation factors up to

    1

    ♦Carrier conditions for use with modulation factors up to 1.0.

  • the area, ABCD, in Figure

    3

    the area, ABCD, in Figure 3. Amplification factor, plate resistance, transconductance, and

  • If the

    205 megacycles

    If the 205D tube is to be used at frequencies higher than 15 megacycles, the plate voltage and

Other

  • Maximum Plate Current

    50 Milliamperes

    Maximum Plate Current 50 Milliamperes

  • Maximiun Plate Dissipation

    14 Watts

    Maximiun Plate Dissipation 14 Watts

  • Maximum Plate Voltage

    400 Volt

    Maximum Plate Voltage 400 Volts

  • Maximum DC Plate Current

    50 Milliamperes

    Maximum DC Plate Current 50 Milliamperes

  • Maximum Plate Dissipation

    14 Watts

    Maximum Plate Dissipation 14 Watts

  • Maximum Non-modulated DC Plate Voltage

    4 Volt

    Maximum Non-modulated DC Plate Voltage 4 0 0 Vo l t s

  • Maximum Modulated DC Plate Voltage

    3 Volt

    Maximum Modulated DC Plate Voltage 3 5 0 Vo l t s

  • frequency of

    30 megacycles

    frequency of 30 megacycles, the maximum ratings should be as follows:

  • Maximum plate voltage

    300 volt

    Maximum plate voltage 300 volts

  • Maximum plate dissipation

    10 watts

    Maximum plate dissipation 10 watts

  • Maximum r-f grid current

    3 amperes

    Maximum r-f grid current 3 amperes