16ATP4 — Cathode Ray Tube

An electrostatic-focus, magnetic-deflection glass picture tube featuring an integral plastic implosion barrier, designed for cathode-drive television receiver applications.

Overview

The 16ATP4 is a 16-inch rectangular glass cathode ray tube (CRT) designed for television display service. It features electrostatic focusing and magnetic deflection with a nominal diagonal deflection angle of 114 degrees. The tube is specifically engineered as a low Grid No. 2 voltage type optimized for cathode-drive operation.

Key design features of the 16ATP4 include lightweight glass construction, a short overall length, a small neck diameter, and a non-ion-trap gun. The fluorescent screen uses a P4 aluminized phosphor to maximize light output and minimize screen charging. Additionally, an external conductive coating is provided which, when grounded, acts as a filter capacitor in conjunction with the internal anode coating.

Mechanical Design and Physical Dimensions

The 16ATP4 is constructed with a rectangular glass bulb (JEDEC designation J125A1) and a spherical gray faceplate. It features an integrated plastic implosion barrier for safety.

The physical dimensions of the tube are highly compact, characterized by a short neck and overall length:

• Overall Length: 10 1/8 ± 1/4 inches
• Neck Length: 4 ± 1/8 inches
• Neck Diameter: 1 1/8 ± 1/8 inches
• Greatest Bulb Dimensions:
  • Diagonal: 15 11/16 + 5/32, - 1/8 inches
  • Width: 13 3/4 ± 1/8 inches
  • Height: 11 5/32 ± 1/8 inches
• Minimum Useful Screen Dimensions (Projected):
  • Diagonal: 14 7/8 inches
  • Horizontal Axis: 12 15/16 inches
  • Vertical Axis: 10 1/4 inches
  • Minimum Useful Area: 125 square inches

The tube utilizes a JEDEC No. J1-21 bulb contact for the high-voltage anode connection. The anode contact is aligned with base pin No. 4 within a tolerance of ± 30 degrees. The base is a JEDEC No. B7-237 or B7-208, which requires a non-rigidly mounted socket with flexible leads to prevent mechanical stress on the glass. The bottom circumference of the base wafer falls within a 1 3/4-inch diameter circle concentric with the bulb axis.

Electrical and Optical Characteristics

The 16ATP4 is designed with a low Grid No. 2 voltage configuration, making it highly suitable for cathode-drive circuitry.

Heater and Warm-Up

The tube is equipped with an indirectly heated cathode. The heater has the following specifications:

• Heater Voltage (Nominal): 6.3 V
• Heater Current: 450 ± 23 mA
• Heater Warm-Up Time: 11 seconds

Electrostatic and Deflection Parameters

• Focusing Method: Electrostatic (Grid No. 4)
• Deflection Method: Magnetic
• Approximate Deflection Angles:
  • Diagonal: 114 degrees
  • Horizontal: 102 degrees
  • Vertical: 84 degrees

Direct Interelectrode Capacitances

• Cathode to all other electrodes: Approximately 5 μμF
• Grid No. 1 to all other electrodes: Approximately 6 μμF
• External conductive coating to anode: 1000 μμF minimum to 1500 μμF maximum

Optical Specifications

• Phosphor: P4 (Aluminized)
• Light Transmittance at Center: Approximately 48%

Basing and Pin Connections

The 16ATP4 uses the 8HR basing diagram. The pin connections, viewed from the bottom of the base, are as follows:

Note that Grid No. 1 is internally connected to both Pin 2 and Pin 6. Pin 5 is omitted from the base configuration.

Ratings and Operating Conditions

The ratings of the 16ATP4 are defined under the Design Maximum System. Unless otherwise specified, all voltage values are positive and measured with respect to Grid No. 1.

Design Maximum Ratings

• Anode Voltage: 11,000 V minimum to 18,000 V maximum
• Grid No. 4 (Focusing Electrode) Voltage: -500 V to +1000 V
• Grid No. 2 Voltage: 40 V minimum to 100 V maximum
• Cathode Voltage:
  • Maximum Positive DC Value: 140 V
  • Maximum Positive Peak Value: 200 V
  • Maximum Negative DC Value: 0 V
  • Maximum Negative Peak Value: 2 V
• Heater Voltage: 5.7 V minimum to 6.9 V maximum
• Maximum Heater-Cathode Voltage:
  • Heater negative with respect to cathode:
    • During warm-up period (not to exceed 15 seconds): 410 V
    • After equipment warm-up period: 180 V
  • Heater positive with respect to cathode: 180 V

Typical Operating Conditions (Cathode-Drive Service)

Under typical cathode-drive operating conditions, the electrode potentials are set as follows:

• Anode Voltage: 15,000 V DC
• Grid No. 4 Voltage: 250 V DC (Individual tubes will achieve satisfactory focus at some value between 0 V and 500 V DC)
• Grid No. 2 Voltage: 50 V DC
• Cathode-to-Grid No. 1 Voltage for Cut-off: 31 V to 49 V DC (defined as visual extinction of the focused raster)

Note on Focus Voltage: The typical focusing electrode voltage is specified at 150 μA anode current on a 12 15/16-inch x 10 1/4-inch pattern (using an RCA 2F21 monoscope or equivalent) with the combined Grid No. 1 bias and video-signal voltage adjusted accordingly.

Maximum Circuit Values

To prevent damage to the tube, the external circuit resistances must be kept within the following limits:

• Maximum Grid No. 1 Circuit Resistance: 1.5 megohms
• Minimum Grid No. 2 Circuit Resistance: 0.1 megohms
• Minimum Focusing Electrode Circuit Resistance: 0.1 megohms

To prevent damage, it is advisable to incorporate protective resistance in both the Grid No. 2 and focusing electrical circuits. If applicable, a single common resistor may be shared between both of these circuits.

Technical Summary

The 16ATP4 is a specialized 16-inch rectangular glass cathode ray tube featuring electrostatic focusing, magnetic deflection, and a 114-degree diagonal deflection angle. Designed for cathode-drive television receiver service, it operates with a low Grid No. 2 voltage (typically 50 V DC) and features a short overall length of 10 1/8 inches. The tube incorporates an integral plastic implosion barrier, an aluminized P4 screen with 48% light transmittance, and an external conductive coating that functions as a filter capacitor. With its compact physical dimensions, small neck diameter, and standardized 8HR basing, the 16ATP4 provides a robust and efficient display solution for its class.