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Voltage Radio Detector Converter ·Pentode-Triode

7258

Combined triode-pentode for oscillator, mixer, frequency-converter, RF, or IF service in television, communications, or mobile receivers.

Directly heatedCold cathodeCommon cathodeDissimilar
Sections
2
Base
-
Socket code
B9A
Base pins
9
Nominal heater
13.5 V / 210 mA

Description

The 7258 combines an independent medium-mu triode and sharp-cutoff pentode; the triode serves oscillator or general amplification duties while the pentode is intended for RF, IF or reactance service in mobile equipment.

Socket description

Small-button Noval 9-contact

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base
-
Socket code
B9A
Base pins
9
Nominal heater voltage
13.5 V
Nominal heater current
210 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

Triode

X-ray radiationInterelectrode capacitances
Plate resistance
4700 Ω
Transconductance
0.0045 S
Amplification factor
21
Max plate voltage
330 V
Max plate dissipation
2.8 W

Published source values promoted where applicable; additional source values retained as parameters.

Section 2

Pentode

X-ray radiationInterelectrode capacitances
Plate resistance
170000 Ω
Transconductance
0.0078 S
Max plate voltage
330 V
Max screen voltage
330 V
Max plate dissipation
2.3 W
Max screen dissipation
0.55 W

Published source values promoted where applicable; additional source 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

1961 Tung Sol

Published operating points and test conditions from this source.

SECTION 1

Triode

Other

  • Plate Voltage

    150 V

    TriodeSection

  • Service

    Low-frequency oscillator or general-purpose amplifier

Characteristic

  • Plate Current

    15 mA

    TriodeSection

SECTION 2

Pentode

Other

  • Plate Voltage

    125 V

    PentodeSection

  • Screen Voltage

    125 V

    PentodeSection

  • Service

    RF / IF / reactance-tube amplifier

Characteristic

  • Plate Current

    12 mA

    PentodeSection

  • Screen Current

    3.8 mA

    PentodeSection

Data set 02

1965 Sylvania Electronic Tubes Vol3

Published operating points and test conditions from this source.

SECTION 1

Triode

Other

  • Heater voltage range

    12 to 15 V

  • Heater-cathode voltage maximum heater negative

    200 V

  • Heater-cathode voltage maximum heater positive DC

    100 V

  • Triode plate voltage maximum

    530 V

  • Pentode plate voltage maximum

    330 V

  • Pentode grid2 dissipation maximum

    0.55 W

Characteristics

  • Heater current at 13.5 V

    210 mA

  • Triode transconductance

    4500 uS

  • Pentode transconductance

    7800 uS

Application

  • Application

    Mobile communications triode-pentode

SECTION 2

Pentode

Characteristics

  • Pentode transconductance

    7800 uS

Data set 03

1966 Tung Sol Electronic Tubes 4 of 4

Published operating points and test conditions from this source.

SECTION 1

Triode

Characteristic

  • Grid-to-plate capacitance

    1.5 pF

    WholeTube

  • Input capacitance

    2 pF

    WholeTube

  • Output capacitance

    1.5 pF

    WholeTube

  • Grid 1 To Plate: Gl Top

    0.04 pf

    PublishedTable

  • Grid To Plate: G To P

    1.5 pf

    PublishedTable

  • Limits Of Applied Voltage

    1 VOLTS

    PublishedTable

  • Heater Negative With Respect To Cathode

    200 VOLTS

    PublishedTable

  • Plate Voltage

    330 VOLTS

    PublishedTable

  • Grid 2 Supply Voltage

    330 VOLTS

    PublishedTable

  • Positive Grid 1 Voltage

    0 VOLTS

    PublishedTable

  • Plate Dissipation

    2.3 WATTS

    PublishedTable

  • Grid 2 Dissipation

    0.55 WATTS

    PublishedTable

  • Fixed Bias

    0.25 MEGOHM

    PublishedTable

  • Cathode 81 As

    1 MEGOHM

    PublishedTable

Other

  • Plate voltage

    150 V

    WholeTube

  • Grid 1 voltage

    -3 V

    WholeTube

SECTION 2

Pentode

Characteristic

  • Grid 1 to plate capacitance

    0.04 pF

    WholeTube

  • Input capacitance

    7 pF

    WholeTube

  • Output capacitance

    2.4 pF

    WholeTube

Other

  • Plate voltage

    125 V

    WholeTube

  • Grid 2 voltage

    125 V

    WholeTube

  • Grid 2 current

    3.8 mA

    WholeTube