16EP4B — Cathode Ray Picture Tube

The 16EP4B is a direct-view cathode ray picture tube designed primarily for television receiver applications. It features a round metal-cone construction, magnetic focus, and magnetic deflection. The tube is designed to display a standard 10" x 13 1/4" television raster.

The 16EP4B belongs to a family of closely related tubes, including the 16EP4 and 16EP4A. These three types are electrically and mechanically identical, with the exception of their faceplate treatments. The 16EP4 has a standard clear faceplate, while both the 16EP4A and 16EP4B incorporate a grey filter faceplate to enhance contrast under ambient light. The 16EP4B is further treated to reduce specular reflection of ambient light.

Construction and Physical Characteristics

The 16EP4B is constructed with a round metal cone body and a glass faceplate. The physical dimensions and mechanical specifications of the tube include:

• Overall Length: 19 5/16 ± 3/8 inches
• Greatest Diameter of Bulb: 15 7/8 ± 1/8 inches
• Minimum Useful Screen Diameter: 14 3/8 inches
• Neck Diameter: 1 7/16 ± 1/16 inches
• Bulb Contact: Metal cone lip
• Base: Small shell duodecal 5-pin (B5-57)
• Basing Configuration: 12D

The metal cone lip serves as the electrical contact for the anode and Grid No. 3. For proper operation, an external single-field ion trap magnet must be positioned on the neck, requiring a cleared space of 3 3/4 inches along the neck.

Optical Specifications

The tube utilizes Phosphor No. 4, which provides a white fluorescent color, a white phosphorescent color, and medium persistence.

The grey filter faceplate of the 16EP4B provides an approximate light transmission of 66 percent at the center of the screen. The anti-reflection treatment on the 16EP4B faceplate reduces the specular reflection of ambient light to approximately 2.5 percent.

Electrical Specifications and Pin Connections

The 16EP4B utilizes an indirectly heated, coated unipotential cathode. The bottom-view pin connections for the 12D basing arrangement are defined as follows:

Direct Interelectrode Capacitances

The approximate direct interelectrode capacitances of the tube structure are:

• Cathode to all other electrodes: 5 µµF
• Grid No. 1 to all other electrodes: 6 µµF

Maximum Ratings (Design Center Values)

The operating limits for the 16EP4B are established under the Design Center rating system:

Heater-Cathode Voltage Limits

To prevent breakdown between the heater and cathode, the peak heater-cathode voltage must not exceed the following limits:

• Heater negative with respect to cathode:
  • During equipment warm-up period (not to exceed 15 seconds): 410 V
  • After equipment warm-up period: 140 V
• Heater positive with respect to cathode: 140 V

The cathode must be returned electrically to one side or to the center-tap of the heater transformer winding.

Typical Operating Conditions and Characteristics

Under typical operating conditions, the 16EP4B is configured with the following electrical parameters:

• DC Anode & Grid No. 3 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): 105 ± 20% mA
• DC Ion Trap Current (approximate, using Standard Coil #111): 80 ± 50% mA

Focusing and Deflection Setup

The 16EP4B utilizes magnetic deflection with an approximate deflection angle of 60 degrees. Focusing is also achieved magnetically.

The typical focusing coil current of 105 ± 20% mA is specified when using a standard focus coil (such as #109 or an equivalent). This current rating is valid when the combined Grid No. 1 bias voltage and video signal voltage are adjusted to produce a highlight brightness of 30 foot-lamberts on a 10" x 13 1/4" picture size. For this operating point, the focus coil must be positioned such that the distance from the reference line to the center of the air gap on the focus coil is exactly 2.75 inches.

Technical Summary

The 16EP4B is a 60-degree magnetic deflection and focus cathode ray picture tube featuring a round metal-cone envelope and a small shell duodecal 5-pin base. Operating with a standard 6.3 V, 0.6 A heater, the tube is designed for an anode operating voltage of 12,000 V (with a design center maximum of 14,000 V). It is distinguished by its grey filter faceplate with an anti-reflection treatment that limits specular reflection of ambient light to 2.5% while maintaining a center light transmission of 66%. Utilizing Phosphor No. 4 for a medium-persistence white display, the tube requires an external single-field ion trap magnet and standard magnetic focusing components to produce a 10" x 13 1/4" television raster.