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

903JB

Special-purpose cathode-ray display tube in the 903 family, intended for radar, monitor, or related visual-display service with phosphor characteristics designated by the JB suffix.

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

Description

Nine-inch radar display CRT with metal-backed screen, magnetic deflection and low-voltage electrostatic focus.

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base
B12A
Socket code
-
Base pins
-
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
15000 V

Promoted fields were populated only where the Ferranti sheet maps cleanly to the locked schema; additional ratings and operating values are retained in TUBE_SECTION_PARAMETER.

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

Other

  • First-anode voltage maximum

    500 V

  • First-anode voltage minimum

    200 V

  • Second-and-fourth-anode voltage minimum

    8000 V

  • Third-anode voltage minimum

    -500 V

  • Third-anode voltage maximum

    500 V

  • First-anode voltage

    300 V

  • Second-and-fourth-anode voltage

    12000 V

  • Third-anode focus voltage minimum

    -300 V

  • Third-anode focus voltage maximum

    300 V

  • Visual cutoff grid voltage minimum

    -70 V

  • Visual cutoff grid voltage maximum

    -30 V

Capacitance

  • Cathode-to-all capacitance maximum

    8 pF

  • Grid-to-all capacitance maximum

    8 pF

  • Anode-to-external-coating capacitance

    750 pF

    Approximate