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

3RPA

Three-inch cathode-ray tube for oscilloscope and instrument display service, using electrostatic focusing and electrostatic deflection. Its specified screen designation identifies the phosphor variant within this compact oscillographic family.

Directly heatedCold cathodeCommon cathodeDissimilarSpecialized
Sections
1
Base
-
Socket code
B12A
Base pins
-
Nominal heater
6.3 V / 600 mA

Description

3-inch direct-view round electrostatic-focus, electrostatic-deflection CRT family for oscillographic display.

Socket description

Duodecal 12-contact

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base
-
Socket code
B12A
Base pins
-
Nominal heater voltage
6.3 V
Nominal heater current
600 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

1 physical section, each with unique specifications.

Section 1

Cathode Ray

X-ray radiationInterelectrode capacitances

No fixed ratings are recorded for this section.

CRT electron-gun/display section; CRT-specific electrical ratings, capacitances, focus and deflection data are stored 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

1965 Sylvania Electronic Tubes Vol3

Published operating points and test conditions from this source.

SECTION 1

Cathode Ray

Characteristics

  • Focusing method

    1 code

    Electrostatic

  • Deflection method

    1 code

    Electrostatic

  • Deflection factor D1-D2 minimum

    146 V/in

  • Deflection factor D1-D2 maximum

    198 V/in

  • Deflection factor D3-D4 minimum

    104 V/in

  • Deflection factor D3-D4 maximum

    140 V/in

  • Useful screen / scan

    1 code

    3-inch round direct-view screen

  • Phosphor designation

    1 code

    Family sheet: P1/P4 variants

Other

  • Anode No. 2 / accelerator voltage maximum

    2750 V

  • Anode No. 2 / accelerator voltage

    2000 V

  • Focusing electrode voltage maximum

    1100 V

  • Focusing electrode voltage minimum

    330 V

  • Focusing electrode voltage maximum

    620 V

  • Grid No. 1 cutoff voltage minimum

    -135 V

  • Grid No. 1 cutoff voltage maximum

    -45 V

  • Peak heater-to-cathode voltage

    140 V

  • Peak voltage between accelerator and any deflection plate

    550 V

  • Grid No. 1 negative bias maximum

    220 V