14B8

Heptode oscillator-converter for superheterodyne radio reception. Its multi-grid structure combines local-oscillator and mixer functions in one tube, translating incoming RF signals to intermediate frequency in series-heater receiver designs.

Directly heatedCold cathodeCommon cathodeDissimilar

Sections: 1
Base: 8X
Socket code: IO
Base pins: 8
Nominal heater: 12.6 V / 150 mA

Description

14B8 — Pentagrid Converter Vacuum Tube

The 14B8 is an indirectly heated pentagrid converter vacuum tube designed for frequency conversion service in radio receivers. It combines the functions of an oscillator and a mixer within a single envelope.

Design and Physical Specifications

The 14B8 is classified as a pentagrid converter. It features an indirectly heated, unipotential cathode and is designed for operation in series-string or standard heater circuits.

Parameter	Specification
Heater Voltage	12.6 V
Heater Current	0.15 A
Cathode Type	Indirectly heated (Htr)
Base Connection	8X
Outline Drawing	9-30

The 8X base configuration provides the necessary pin connections for the heater, cathode, plate, screen, and control grids.

Electrical Ratings and Operating Conditions

The 14B8 is characterized by specific maximum ratings and typical operating parameters when employed in converter service.

Maximum Ratings

The maximum design-center limits for the primary electrodes are:

Maximum Plate Voltage: 300 V
Maximum Screen Voltage: 100 V

Typical Converter Operation

Under typical operating conditions as a converter, the electrical parameters are defined as follows:

Parameter	Value
Plate Voltage	250 V
Screen Voltage	100 V
Negative Grid Voltage	3.0 V
Plate Current	3.5 mA
Screen Current	2.7 mA
Plate Resistance ( $R_p$ )	360,000 ̩ (approximate)
Conversion Transconductance ( $G_m$ )	550 µmhos

Oscillator Section Operating Conditions

The oscillator portion of the pentagrid structure operates with the following parameters:

Oscillator Grid Current ( $I_{g1}$ ): 0.4 mA
Oscillator Grid Resistor ( $R_{g1}$ ): 50,000 ̩
Oscillator Plate Voltage ( $E_{c2}$ ): 250 V supplied through a 20,000 ̩ series resistor
Oscillator Plate Current ( $I_{c2}$ ): 4.0 mA

Technical Summary

The 14B8 is an eight-pin (8X base) pentagrid converter featuring a 12.6 V, 0.15 A heater. It is engineered to perform frequency conversion with a maximum plate rating of 300 V and a screen rating of 100 V. In typical converter service at 250 V on the plate and 100 V on the screen, it exhibits a conversion transconductance of 550 µmhos and an approximate plate resistance of 360,000 ̩. The integrated oscillator section is typically operated with a 0.4 mA grid current through a 50,000 ̩ grid resistor, and an oscillator plate current of 4.0 mA when connected to a 250 V supply via a 20,000 ̩ resistor.

Socket description

International Octal

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base: 8X
Socket code: IO
Base pins: 8
Nominal heater voltage: 12.6 V
Nominal heater current: 150 mA
Parallel heater voltage: -
Parallel heater current: -
Series capable: No

8X - 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

Heptode

X-ray radiationInterelectrode capacitances

Plate resistance: 360000 Ω
Transconductance: 0.00055 S
Max plate voltage: 300 V
Max screen voltage: 100 V

Published maximum ratings, operating characteristics, and continuation data reviewed.

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

195X General Electric Essential Characteristics

Published operating points and test conditions from this source.

SECTION 1

Heptode

Other

Maximum plate voltage
300 V
Published handbook rating
Maximum screen voltage
100 V
Published handbook rating
Plate voltage
250 V
ClassA
Screen voltage
100 V
ClassA
Control-grid bias
3 V
ClassA
Plate current
3.5 mA
ClassA
Screen current
2.7 mA
ClassA
Oscillator plate supply
250 V
Converter Oscillator
Oscillator plate current
4 mA
Converter Oscillator
Oscillator grid resistor
53000 ohm
Converter Oscillator

Characteristic

Plate resistance
360000 ohm
Published handbook characteristic
Transconductance
550 µS
Published handbook characteristic
Heater voltage
12.6 V
Published heater rating
Heater current
150 mA
Published heater rating