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Tube Tinker — Electron Tube Database
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Specialized - Cathode Ray ·CathodeRay

321AM

Three-inch high-resolution cathode-ray display tube with magnetic focusing and deflection and an optically flat metal-backed screen. Approximately 1000-line-per-inch center resolution supports detailed precision display applications.

Directly heatedCold cathodeCommon cathodeDissimilarSpecialized
Sections
1
Base
B12A
Socket code
-
Base pins
12
Nominal heater
6.3 V / 300 mA

Description

Three-inch high-resolution magnetic-focus, magnetic-deflection cathode-ray display tube with optically flat metal-backed screen.

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base
B12A
Socket code
-
Base pins
12
Nominal heater voltage
6.3 V
Nominal heater current
300 mA
Parallel heater voltage
-
Parallel heater current
-
Series capable
No

B12A - 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

Cathode Ray

X-ray radiationInterelectrode capacitances
Max plate voltage
25000 V

Ratings, characteristics, typical operating points, and capacitances were extracted from the supplied Ferranti datasheet.

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

1963 Ferranti

Published operating points and test conditions from this source.

SECTION 1

Cathode Ray

Characteristic

  • HeaterOrFilamentVoltage

    6.3 V

  • HeaterOrFilamentCurrent

    300 mA

  • FocusingMethod

    Magnetic

  • DeflectionMethod

    Magnetic

  • Deflection Angle

    60 degree

  • ScreenConstruction

    Metal-backed

  • UsefulScreenDiameterMinimum

    85 mm

  • GridVoltageForVisualCutoff

    AnodeVoltage/210

  • CathodeToAllCapacitanceMaximum

    8 pF

  • GridToAllCapacitanceMaximum

    8 pF

Other

  • HeaterCathodeVoltageMaximum

    200 V

    HeaterNegative

  • HeaterCathodeVoltageMaximum

    200 V

    HeaterPositive

  • GridCathodeResistanceMaximum

    1.5 Mohm

  • AnodeVoltageTypical

    -

  • GridVoltageForVisualCutoff

    -90 V

  • ScreenResolution

    1000 lines/in

    ScreenCentre