15CP4 — Electromagnetic Cathode Ray Tube

The 15CP4 is an electromagnetic cathode ray tube (CRT) designed primarily for direct-view black-and-white television receivers. It features a glass bulb construction and produces a rectangular picture of approximately 9" x 12" with good definition. The tube utilizes magnetic deflection and magnetic focusing, and it requires an external ion-trap magnet to prevent the formation of ion-spot blemishes on the screen.

Optical and Screen Characteristics

The screen of the 15CP4 is designed to provide a clear, high-contrast display suitable for television viewing. Its primary characteristics include:

• Fluorescence and Phosphorescence: White
• Persistence: Medium
• Deflection and Focus: Magnetic
• Deflection Angle: Approximately 50 degrees
• Ion-Trap: Magnetic (requires an external ion-trap magnet)
• Bulb Contact: Recessed small cavity for the anode connection

Physical Dimensions and Mounting

The 15CP4 is a large-format television tube of its era. It can be operated in any mounting position. The physical dimensions of the glass envelope are specified as follows:

Heater and Base Connections

The tube incorporates a coated unipotential cathode. The heater is designed to operate on either alternating current (AC) or direct current (DC).

• Heater Voltage: 6.3 V
• Heater Current: 0.6 A

The 15CP4 uses a small shell duodecal 5-pin base (utilizing the 12D basing arrangement). The pin connections, viewed from the bottom of the base, are as follows:

Electrical Ratings

The maximum ratings for the 15CP4 are interpreted according to the RMA Standard M8-210 rating system. Operating the tube beyond these limits may impair performance or cause permanent damage.

Direct Interelectrode Capacitances

• Grid #1 to all other electrodes: 6.5 ΙΙF
• Cathode to all other electrodes: 5 ΙΙF

Typical Operating Conditions and Characteristics

Under typical operating conditions, the 15CP4 requires specific voltage and current levels to maintain optimal picture brilliance and definition.

Operating Considerations and Performance Notes

• Anode Voltage Limits: While the tube is rated for typical operation between 9,000 and 15,000 V, a decrease in anode voltage below 9,000 V results in a noticeable reduction in picture brilliance and definition. In general, the anode voltage should not be allowed to fall below this 9,000 V threshold.
• Grid #2 Voltage Limits: Similarly, the brilliance and definition of the display will decrease if the Grid #2 voltage is reduced. For satisfactory performance, the Grid #2 voltage should not be less than 125 V.

Technical Summary

The 15CP4 is a 15-inch class electromagnetic cathode ray tube designed for direct-view black-and-white television applications. It features a 50-degree deflection angle, medium-persistence white phosphor, and requires external magnetic focusing, deflection, and ion-trap components. Operating with a standard 6.3 V, 0.6 A heater, the tube is capable of handling anode potentials up to 15,000 V, delivering a clear 9" x 12" picture when operated within its recommended typical conditions.