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Specialized - Cathode Ray ·CathodeRay

19AP4C

P4 high-voltage cathode-ray picture-display tube with magnetic focusing and deflection; this 19AP4C variant differs principally in faceplate treatment, with manufacturer documentation warning about X-ray shielding above 16 kV.

Directly heatedCold cathodeCommon cathodeDissimilarSpecialized
Sections
1
Base
12D
Socket code
DUODECAL5
Base pins
5
Nominal heater
6.3 V / 600 mA

Description

19AP4C — Direct-View Metal-Shell Cathode Ray Tube

A direct-view, metal-shell picture tube designed for television receiver applications, featuring a grey filter faceplate and an aluminized screen.

Overview

The 19AP4C is a direct-view cathode ray tube (CRT) designed primarily for television receivers. It is a member of the 19AP4 family, which includes the 19AP4, 19AP4A, 19AP4B, and 19AP4D. While sharing the same electrical and physical dimensions as other members of its family, the 19AP4C is distinguished by its specific faceplate design, which features a grey filter faceplate and an aluminized screen to improve picture contrast and brightness.

The tube utilizes magnetic deflection and magnetic focusing, requiring an external single-field ion trap magnet to prevent ion burn on the phosphor screen. It provides a standard rectangular television raster with nominal dimensions of 11 3/4 inches by 15 3/4 inches.

Mechanical Specifications and Base Configuration

The 19AP4C features a round metal-cone construction with a unipotential cathode. The physical dimensions of the envelope are as follows:

  • Overall Length: 21 1/2 ± 1/2 inches
  • Greatest Diameter of Bulb: 18 5/8 ± 1/8 inches
  • Minimum Useful Screen Diameter: 17 3/8 inches

The electrical connection to the high-voltage anode and Grid No. 3 is made directly via the metal shell lip of the bulb. The remaining electrical connections are routed through a small shell duodecal 5-pin base (B5-57), which conforms to the 12D basing diagram.

Pinout Connections

The pin connections, viewed from the bottom of the tube base, are assigned as follows:

Pin NumberConnection
Pin 1Heater
Pin 2Grid No. 1 (Control Grid)
Pin 10Grid No. 2 (Screen Grid)
Pin 11Cathode
Pin 12Heater
Metal Shell LipGrid No. 3 and Anode

Optical and Deflection Characteristics

The 19AP4C is equipped with a No. 4 Phosphor, which produces a white fluorescent and white phosphorescent light with medium persistence. This phosphor is optimized for black-and-white television reproduction. The faceplate is constructed from a grey filter glass that provides approximately 66% light transmission at the center, reducing ambient light reflections and enhancing contrast.

Deflection and focusing are achieved magnetically:

  • Deflection Angle (Approximate): 66 degrees
  • Focusing Method: Magnetic, requiring an external focusing coil
  • Ion Trap: External single-field ion trap magnet

Electrical Ratings

The following limits are established under the Design Center rating system. Operating the tube beyond these limits may impair performance or cause permanent damage.

ParameterRating
Heater Voltage6.3 V
Heater Current0.6 A
Maximum DC Anode Voltage19,000 V
Maximum DC Grid No. 2 Voltage410 V
Maximum DC Grid No. 1 Negative-Bias Value125 V
Maximum DC Grid No. 1 Positive-Bias Value0 V
Maximum Grid No. 1 Positive-Peak Value2 V

Heater-Cathode Voltage Limits

  • Heater negative with respect to cathode: 410 V during the warm-up period (not to exceed 15 seconds); 150 V after the equipment has warmed up.
  • Heater positive with respect to cathode: 150 V.

Safety Note: X-ray radiation shielding may be necessary if the tube is operated at anode voltages exceeding 16,000 V.

Typical Operating Conditions

Under typical operating conditions in a television receiver, the 19AP4C is operated with the following parameters:

  • DC Anode Voltage: 12,000 V
  • DC Grid No. 2 Voltage: 300 V
  • DC Grid No. 1 Voltage (for visual extinction of undeflected focused spot): -33 V to -77 V
  • DC Focusing Coil Current (Approximate): 140 ± 20% mA
    • Condition: Measured using a standard focus coil (No. 106 or equivalent) positioned with the center of its air gap 3.0 inches from the reference line. The combined Grid No. 1 bias and video signal must be adjusted to produce a highlight brightness of 18 foot-lamberts on the 11 3/4" x 15 3/4" picture area.
  • DC Ion Trap Current (Approximate): 75 ± 50% mA (using a standard coil No. 111)

Circuit Design and Capacitances

To ensure stable operation and prevent grid emission or bias instability, the control grid circuit must not exceed a maximum resistance limit:

  • Maximum Grid No. 1 Circuit Resistance: 1.5 Megohms

The interelectrode capacitances of the tube are relatively low, minimizing loading on the video amplifier and drive circuits:

  • Cathode to all other electrodes (Approximate): 5 pF
  • Grid No. 1 to all other electrodes (Approximate): 7 pF

Technical Summary

The 19AP4C is a 66-degree magnetic deflection, magnetically focused cathode ray tube featuring a round metal-shell envelope. It operates with a standard 6.3 V, 0.6 A heater and is capable of handling anode voltages up to 19,000 V. Its grey filter faceplate (66% transmission) and aluminized screen distinguish it from other members of the 19AP4 family, providing improved contrast and brightness for direct-view television applications. With its standard duodecal 5-pin base, external single-field ion trap, and typical anode operating potential of 12,000 V, the 19AP4C represents a classic implementation of mid-century metal-cone television display technology.

Socket description

Small-shell Duodecal 5-contact CRT base

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base
12D
Socket code
DUODECAL5
Base pins
5
Nominal heater voltage
6.3 V
Nominal heater current
600 mA
Parallel heater voltage
-
Parallel heater current
-
Series capable
No

12D - 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
19000 V
Max screen voltage
410 V

CRT-specific electrode, focusing and deflection data retained as parameters.

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

1961 Tung Sol

Published operating points and test conditions from this source.

SECTION 1

Cathode Ray

Other

  • Maximum Anode Voltage

    19000 V

  • Typical Anode Voltage

    12000 V

  • Maximum Grid2 Voltage

    410 V

  • Typical Grid2 Voltage

    300 V

Characteristic

  • DeflectionAngleApproximate

    66 degree

  • FocusingMethod

    Magnetic

  • DeflectingMethod

    Magnetic

  • PhosphorNumber

    4

  • FluorescentColor

    White

  • Persistence

    Medium

  • FaceplateVariant

    Grey filter faceplate; aluminized screen

Data set 02

1966 Tung Sol Electronic Tubes 4 of 4

Published operating points and test conditions from this source.

SECTION 1

Cathode Ray

Characteristics

  • DEFLECTION ANGLE (APPROX.)

    66 degrees

    Published CRT datasheet value; multiple values on a row correspond to separate source-table conditions or limits.

  • FACEPLATE LIGHT TRANSMISSION

    66 percent

    Published CRT datasheet value; multiple values on a row correspond to separate source-table conditions or limits.

  • HEATER

    6.3 V

    Published CRT datasheet value; multiple values on a row correspond to separate source-table conditions or limits.

  • A IF THIS TUBE IS OPERATED AT VOLTAGES IX E%LESS OF 16,000 VOLTS %—RAY RADIATION SHIELD LNG MAY — value 1

    16 V

    Published CRT datasheet value; multiple values on a row correspond to separate source-table conditions or limits.

  • A IF THIS TUBE IS OPERATED AT VOLTAGES IX E%LESS OF 16,000 VOLTS %—RAY RADIATION SHIELD LNG MAY — value 2

    0 V

    Published CRT datasheet value; multiple values on a row correspond to separate source-table conditions or limits.

  • DC ANODE

    12 V

    Published CRT datasheet value; multiple values on a row correspond to separate source-table conditions or limits.

  • DC GRID #2 VOLTAGE — value 1

    2 V

    Published CRT datasheet value; multiple values on a row correspond to separate source-table conditions or limits.

  • DC GRID #2 VOLTAGE — value 2

    300 V

    Published CRT datasheet value; multiple values on a row correspond to separate source-table conditions or limits.

  • DC FOCUSING COIL CURRENTC (APPROX.) — value 1

    140 mA

    Published CRT datasheet value; multiple values on a row correspond to separate source-table conditions or limits.

  • DC FOCUSING COIL CURRENTC (APPROX.) — value 2

    20 mA

    Published CRT datasheet value; multiple values on a row correspond to separate source-table conditions or limits.

  • G FOR STANDARD FOCUS COIL 4106, OR EQUIVALENT S WITH THE COMBINED GRID N1 BIAS VOLTAGE AMD

    4106 V

    Published CRT datasheet value; multiple values on a row correspond to separate source-table conditions or limits.

  • VIDEO SIGNAL VOLTAGE ADJUSTED TO PRODUCE A XiGnL IGnT BRIGHTNESS OF 18 F00T LANBERTS ON A

    18 V

    Published CRT datasheet value; multiple values on a row correspond to separate source-table conditions or limits.

  • 11 j/4" % 15 j/R" PICTURE SIZE. DISTANCE FROM REFERENCE LINE TO CENTER OF 41R GAP ON FOCUS — value 1

    4

    Published CRT datasheet value; multiple values on a row correspond to separate source-table conditions or limits.

  • 11 j/4" % 15 j/R" PICTURE SIZE. DISTANCE FROM REFERENCE LINE TO CENTER OF 41R GAP ON FOCUS — value 2

    15

    Published CRT datasheet value; multiple values on a row correspond to separate source-table conditions or limits.

  • 11 j/4" % 15 j/R" PICTURE SIZE. DISTANCE FROM REFERENCE LINE TO CENTER OF 41R GAP ON FOCUS — value 3

    41

    Published CRT datasheet value; multiple values on a row correspond to separate source-table conditions or limits.

Other

  • MAXIMUM DC ANODE

    19000 V

    Published CRT datasheet value; multiple values on a row correspond to separate source-table conditions or limits.

  • MAXIMUM DC GRID #2 VOLTAGE — value 1

    2 V

    Published CRT datasheet value; multiple values on a row correspond to separate source-table conditions or limits.

  • MAXIMUM DC GRID #2 VOLTAGE — value 2

    410 V

    Published CRT datasheet value; multiple values on a row correspond to separate source-table conditions or limits.

  • MAXIMUM GRID #1 VOLTAGE

    1 V

    Published CRT datasheet value; multiple values on a row correspond to separate source-table conditions or limits.

  • MAXIMUM GRID #1 CIRCUIT RESISTANCE — value 1

    1 mA

    Published CRT datasheet value; multiple values on a row correspond to separate source-table conditions or limits.

  • MAXIMUM GRID #1 CIRCUIT RESISTANCE — value 2

    1.5 mA

    Published CRT datasheet value; multiple values on a row correspond to separate source-table conditions or limits.