16DP4A — Cathode-Ray Picture Tube

The 16DP4A is a 16-inch round, glass, direct-view cathode-ray picture tube designed primarily for television receiver applications. It features magnetic focusing and magnetic deflection with an approximate deflection angle of 60 degrees. The tube incorporates an electron gun designed for use with an external double-field ion-trap magnet and utilizes a unipotential cathode.

The 16DP4A is closely related to the standard 16DP4. The two types share identical electrical and mechanical dimensions, with the sole distinction residing in their faceplate construction:

• 16DP4: Features a clear glass faceplate.
• 16DP4A: Equipped with a gray filter faceplate designed to enhance picture contrast and detail under high ambient light conditions.

Mechanical Design and Physical Dimensions

The 16DP4A is constructed with a round glass bulb and a spherical faceplate. Its physical dimensions and mechanical characteristics are as follows:

• Overall Length: 20 3/4 ± 1/4 inches
• Greatest Diameter of Bulb: 15 7/8 ± 1/8 inches
• Minimum Useful Screen Diameter: 14 1/2 inches
• Neck Length: 7 5/8 inches
• Bulb Number (ASA Designation): J127B
• Bulb Contact: Recessed small cavity cap (JETEC No. J1-21)
• Base: Small-shell duodecal 5-pin (JETEC No. B5-57)
• Basing Designation: 12D
• Mounting Position: Any
• Net Weight (Approximate): 16 1/2 pounds
• Raster / Picture Size: Provides a picture size of approximately 10 1/4 by 14 1/2 inches (or 14 1/2 by 10 7/8 inches with rounded sides).

The alignment of the recessed bulb contact (anode terminal) is oriented such that it aligns with the position of pin number 3. The alignment tolerance is specified as ±10 degrees by some sources and ±30 degrees by others. The yoke reference line is determined by the plane of the upper edge of a standard reference-line gage (such as RETMA No. 112) when resting on the cone.

Electron Gun, Heater, and Basing Connections

The 16DP4A utilizes an indirectly heated, coated unipotential cathode. The electrical requirements for the heater and the interelectrode capacitances of the gun structure are:

The 12D duodecal base configuration provides the following pin connections, viewed from the bottom of the tube:

• Pin 1: Heater
• Pin 2: Grid No. 1
• Pin 10: Grid No. 2
• Pin 11: Cathode
• Pin 12: Heater
• Anode Cap: Recessed small cavity cap (J1-21), which connects internally to the anode and Grid No. 3.

Optical Characteristics

The tube utilizes a phosphor screen with the following properties:

• Phosphor Number: P4 (Sulfide Type)
• Fluorescent Color: White
• Phosphorescent Color: White
• Persistence: Short to Medium
• Faceplate Light Transmission: The gray filter faceplate of the 16DP4A has an approximate light transmission of 70% to 73% at the center.

Electrical Ratings and Operating Conditions

The operating limits and typical characteristics of the 16DP4A must be carefully observed to ensure proper performance and longevity.

Design-Center Maximum Ratings

These ratings represent the maximum permissible values under the standard design-center system for cathode-ray tubes:

• Maximum DC Anode Voltage: 15,000 V
• Maximum DC Grid No. 2 Voltage: 410 V
• Maximum Grid No. 1 Voltage:
  • DC Negative-Bias Value: 125 V
  • DC Positive-Bias Value: 0 V
  • Positive-Peak Value: 2 V
• Maximum DC Peak Heater-Cathode Voltage:
  • Heater Negative with Respect to Cathode: 125 V (During a warm-up period not exceeding 15 seconds, a transient peak of up to 410 V is permissible).
  • Heater Positive with Respect to Cathode: 125 V
• Maximum Grid No. 1 Circuit Resistance: 1.5 Megohms

Typical Operating Conditions

Under typical operating conditions, the tube is set up with the following parameters:

• DC Anode Voltage: 12,000 V (Note: Brilliance and focus quality decrease with decreasing anode voltage. In general, the anode voltage should not be operated below 9,000 V).
• DC Grid No. 2 Voltage: 250 V to 300 V
• DC Grid No. 1 Voltage (for visual extinction of the focused spot or raster): -27 V to -72 V (specifically -27 V to -63 V when Grid No. 2 is at 250 V, and -28 V to -72 V when Grid No. 2 is at 300 V).
• Focusing Coil Current (Approximate):
  • 101 mA DC when using a RETMA No. 109 focusing coil positioned with the center of its air gap at 4 1/8 inches from the yoke reference line.
  • 115 mA ± 15% DC when using a standard No. 109 focusing coil positioned with the center of its air gap at 3.25 inches from the reference line.
• Ion-Trap Magnet Adjustment:
  • Requires an external double-field ion-trap magnet.
  • The approximate field intensity is 35 Gausses, which is equivalent to an operating current of approximately 109 mA to 120 mA through a standard No. 108 ion-trap coil adjusted to the optimum position.

Technical Summary

The 16DP4A is an all-glass, 16-inch round cathode-ray picture tube designed for television display applications. It features a gray-tinted faceplate with 70% to 73% light transmission to improve contrast under ambient light, distinguishing it from the clear-faced 16DP4. Operating with a 6.3 V, 0.6 A heater, the tube utilizes magnetic focus and magnetic deflection (60-degree angle) and requires an external double-field ion-trap magnet. Under typical operating conditions, it runs at an anode voltage of 12,000 V (with a design-center maximum of 15,000 V) and a Grid No. 2 voltage of 250 V to 300 V, producing a high-quality white display on its P4 phosphor screen.