16GP4C — Direct-View Television Picture Tube

A 16-inch class, round metal-cone cathode-ray tube featuring a clear glass, frosted faceplate, designed for television receiver applications.

Overview

The 16GP4C is a direct-view cathode-ray picture tube designed primarily for television display applications. It features a round metal-cone construction, magnetic focus, and magnetic deflection. The 16GP4C belongs to a family of four closely related picture tubes—comprising the 16GP4, 16GP4A, 16GP4B, and 16GP4C—which share identical electrical, mechanical, and basic optical characteristics.

The primary distinction among these four types lies in their faceplate treatments:

• 16GP4: Grey filter faceplate
• 16GP4A: Clear glass faceplate
• 16GP4B: Grey filter, frosted faceplate
• 16GP4C: Clear glass, frosted faceplate

The 16GP4C is specifically configured with a clear glass, frosted faceplate to reduce specular reflection of ambient light while maintaining high light transmission.

Optical and Mechanical Characteristics

The 16GP4C is designed to display a standard 10" x 13 1/4" television raster. Its optical and physical specifications are highly standardized to ensure compatibility with contemporary television chassis designs.

Optical Specifications

• Phosphor Number: No. 4
• Fluorescent Color: White
• Phosphorescent Color: White
• Persistence: Medium
• Faceplate Light Transmission at Center: Approximately 65%
• Specular Reflection of Ambient Light: While the frosted grey-filter variant (16GP4B) is rated at 2.5% specular reflection, the frosted clear-glass 16GP4C provides a balanced alternative that diffuses reflections through its frosted surface.

Mechanical Dimensions and Basing

• Overall Length: 17 11/16 inches maximum
• Greatest Diameter of Bulb: 15 7/8 ± 1/8 inches
• Minimum Useful Screen Diameter: 14 3/8 inches
• Bulb Contact: Metal shell lip, which serves as the electrical connection for the anode and Grid No. 3
• Base: Small shell duodecal 5-pin base (designation B5-57)
• Basing Configuration: 12D

The underside pin connections for the 12D basing arrangement are:

• Pin 1: Heater
• Pin 2: Grid No. 1
• Pin 10: Grid No. 2
• Pin 11: Cathode
• Pin 12: Heater
• Metal Shell Lip: Anode / Grid No. 3

A physical clearance of 4 inches along the neck must be kept entirely clear for the installation and adjustment of an external single-field ion trap magnet.

Electrical Ratings and Operating Conditions

The electrical design of the 16GP4C requires high-voltage anode operation and precise magnetic focusing and deflection fields.

Design Center Ratings

The following maximum ratings are established under the design center system:

• Heater Voltage: 6.3 Volts
• Heater Current: 0.6 Ampere
• Maximum DC Anode & Grid No. 3 Voltage: 14,000 Volts
• Maximum DC Grid No. 2 Voltage: 410 Volts
• Maximum Grid No. 1 Voltage:
  • DC Negative-bias value: 125 Volts
  • DC Positive-bias value: 0 Volts
  • Positive-peak value: 2 Volts
• Maximum DC Peak Heater-Cathode Voltage:
  • Heater negative with respect to cathode during warm-up (not to exceed 15 seconds): 410 Volts
  • Heater negative with respect to cathode after warm-up: 150 Volts
  • Heater positive with respect to cathode: 150 Volts

To prevent thermal damage and ensure safe operation, the product of the anode voltage and the average anode current must be limited to a maximum of 6 Watts.

Typical Operating Conditions

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

• DC Anode & Grid No. 3 Voltage: 12,000 Volts. (Note: Brilliance and definition decrease with decreasing anode voltage. In general, the anode voltage should not be operated below 10,000 Volts).
• DC Grid No. 2 Voltage: 300 Volts
• DC Grid No. 1 Voltage: -33 to -77 Volts (for visual extinction of an undeflected, focused spot)
• DC Focusing Coil Current: Approximately 100 mA when using a standard focus coil (such as No. 109 or equivalent). This current is specified with the combined Grid No. 1 bias and video signal voltage adjusted to produce a highlight brightness of 30 foot-lamberts on the standard 10" x 13 1/4" picture size. The distance from the reference line to the center of the focus coil's air gap must be maintained at 3 inches.
• Ion Trap Magnet Strength:
  • 23 Gausses for the 16GP4 and 16GP4C
  • 35 Gausses for the 16GP4A and 16GP4B

Circuit Values and Capacitances

• Maximum Grid No. 1 Circuit Resistance: 1.5 Megohms
• Direct Interelectrode Capacitances (Approximate):
  • Cathode to all other electrodes: 5 µµF (pF)
  • Grid No. 1 to all other electrodes: 6 µµF (pF)

Technical Summary

The 16GP4C is a 16-inch class, round metal-cone cathode-ray tube featuring a clear glass, frosted faceplate. It operates with a 6.3 V, 0.6 A heater and is designed for magnetic focus and deflection with a 70-degree deflection angle. Utilizing Phosphor No. 4 for a medium-persistence white display, it is capable of presenting a 10" x 13 1/4" television raster. The tube requires an external single-field ion trap magnet (rated at 23 Gausses for the 16GP4C) and operates typically at an anode voltage of 12,000 Volts (with a design center maximum of 14,000 Volts). Its physical interface is supported by a small shell duodecal 5-pin base (B5-57), with high-voltage anode connection made directly to the metal shell lip.