Skip to main content
Tube Tinker — Electron Tube Database
Alternatives & variationsDownload PDF datasheet

Voltage Pentode ·Pentode

5A128B

Standard Telephones pentode with manufacturer-specified technical characteristics, ratings, and operating information. The available source establishes signal pentode service but does not provide sufficiently explicit application wording to justify a narrower functional classification.

Directly heatedCold cathodeCommon cathodeDissimilar
Sections
1
Base
-
Socket code
B5
Base pins
5
Nominal heater
4 V / -

Description

5A128B Pentode. Technical characteristics, ratings, and operating information are provided in the approved Standard Valves datasheet.

Socket description

European 5-pin base

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base
-
Socket code
B5
Base pins
5
Nominal heater voltage
4 V
Nominal heater current
-
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

Pentode

X-ray radiationInterelectrode capacitances
Max plate voltage
250 V
Max screen voltage
100 V

Ratings and characteristics extracted from 5A128B.pdf.

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

1946 Standard Telephone and Cables

Published operating points and test conditions from this source.

SECTION 1

Pentode

Other

  • Voltage

    4 v

  • Grid to anode

    0.007 pF

  • Inpu

    10.7 pF

  • Qutpu

    8 pF

  • Maximum direct screen voltage

    100 A

  • Maximum direct anode curren

    9 mA

  • Anode voltage 250 200

    150 volts

  • Control grid bias ... —1.5 —I1.5

    -1.5 volts

  • Screen grid voltage... 100 100

    100 volts

  • Anode current ... 3.9 38

    3.7 mA

  • Load 50,000 46,000

    30000 ohms

  • Output 0.315 0.258

    0.175 watts

  • April 1946

    5 A

  • April 1946

    5 A

  • April 1946

    5 A

Characteristic

  • Mutual conductance \Tge:s%(?e a:,\g _2_'22\\;

    3 mA