16GP4B — Direct-View Television Picture Tube

The 16GP4B is a round, metal-shell direct-view cathode ray picture tube designed primarily for television receiver applications. It features magnetic focus and deflection, a unipotential cathode, and requires an external single-field ion trap magnet. The tube is part of a family of closely related designations, including the 16GP4, 16GP4A, and 16GP4C, sharing identical electrical and mechanical structures but differing in faceplate treatment.

Optical and Faceplate Characteristics

The 16GP4B is specifically distinguished from other members of its family by its faceplate construction, which consists of a frosted grey filter glass. This configuration is designed to control reflections and enhance contrast under ambient lighting conditions. In comparison:

• 16GP4: Grey filter faceplate (non-frosted)
• 16GP4A: Clear glass faceplate (non-frosted)
• 16GP4B: Grey filter, frosted faceplate
• 16GP4C: Clear glass, frosted faceplate

The faceplate of the 16GP4B provides a light transmission of approximately 65 percent at the center. Due to its frosted grey filter treatment, the specular reflection of ambient light is limited to 2.5 percent.

The tube utilizes Phosphor No. 4, which produces a white fluorescence and a white phosphorescence with medium persistence. The standard raster size produced on the screen is 10 inches by 13 1/4 inches.

Mechanical Construction and Basing

The 16GP4B features a round metal cone construction with a metal shell lip serving as the anode terminal. The physical dimensions and mechanical characteristics of the tube include:

The neck of the tube requires a clear space of 4 inches to accommodate the external ion trap magnet.

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

• 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

Electrical Ratings and Operating Conditions

The electrical design of the 16GP4B operates under specified design center maximum ratings and typical operating conditions.

Heater and Interelectrode Capacitances

The tube is equipped with an indirectly heated unipotential cathode. The nominal heater requirements and approximate direct interelectrode capacitances are:

• Heater Voltage: 6.3 Volts
• Heater Current: 0.6 Ampere
• Cathode to all other electrodes: 5 µµF
• Grid No. 1 to all other electrodes: 6 µµF

Design Center Maximum Ratings

To ensure reliable operation, the following maximum limits must not be exceeded:

• Maximum DC Anode and 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 period not exceeding 15 seconds): 410 Volts
  • Heater negative with respect to cathode (after equipment warm-up): 150 Volts
  • Heater positive with respect to cathode: 150 Volts
• Anode Power Limit: 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 and Grid No. 3 Voltage: 12,000 Volts (Brilliance and definition decrease with decreasing anode voltage; the anode voltage should generally 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 the undeflected focused spot).
• DC Focusing Coil Current: Approximately 100 mA when using a standard focus coil (such as focus coil #109 or equivalent). This is specified with the combined Grid No. 1 bias voltage and video signal voltage adjusted to produce a highlight brightness of 30 foot-lamberts on a 10-inch by 13-1/4-inch picture size, with the distance from the reference line to the center of the air gap on the focus coil set to 3 inches.
• Ion Trap Magnet: The 16GP4B (along with the 16GP4A) requires a rated strength of 35 Gausses for its external single-field ion trap magnet, whereas the 16GP4 and 16GP4C require 23 Gausses.
• Maximum Grid No. 1 Circuit Resistance: 1.5 Megohms.

Technical Summary

The 16GP4B is a 70-degree magnetic deflection, magnetically focused television picture tube featuring a round metal construction and a frosted grey filter faceplate. Operating with a 6.3 V, 0.6 A heater, it provides a 10-inch by 13-1/4-inch raster with a medium-persistence white Phosphor No. 4. It is characterized by its 12,000 V typical anode operating potential, a 35 Gauss ion trap magnet requirement, and a duodecal 5-pin base. The frosted grey faceplate reduces specular reflection of ambient light to 2.5% while maintaining a center light transmission of 65%, making it optimized for high-contrast television displays.