14CP4 — Rectangular Cathode-Ray Picture Tube

The 14CP4 is an all-glass, direct-view cathode-ray picture tube designed primarily for television receiver applications. It features a space-saving rectangular bulb shape, a spherical gray neutral-density faceplate to enhance picture contrast and detail under high ambient light conditions, and an electron gun designed for use with an external single-field ion-trap magnet. The tube utilizes magnetic focusing and magnetic deflection.

Mechanical Specifications and Physical Dimensions

The 14CP4 is constructed with a rectangular glass bulb and a spherical gray faceplate. The faceplate has an approximate light transmission of 74 percent at its center.

The physical dimensions and mechanical characteristics of the tube include:

• Overall Length: 16-3/4 ± 3/8 inches
• Greatest Bulb Dimensions:
  • Diagonal: 13-11/16 ± 1/8 inches
  • Width: 12-5/8 ± 1/8 inches
  • Height: 9-3/4 ± 1/8 inches
• Minimum Useful Screen Dimensions:
  • Diagonal: 12-1/2 inches
  • Width: 11-3/8 inches (or a picture width of 11-1/2 inches in early specifications)
  • Height: 8-1/2 inches (or a picture height of 8-5/8 inches in early specifications)
• Neck Length: 7-1/2 inches
• Net Weight: Approximately 10-1/4 pounds
• Bulb Number (ASA Designation): J109-1/2-C1
• Bulb Contact: Recessed small-cavity cap (JETEC No. J1-21)
• Base: Small-shell Duodecal 5-Pin (JETEC No. B5-57)
• Basing Designation: JETEC 12N
• Mounting Position: Any
• Bulb Contact Alignment: The anode contact aligns with the Pin No. 6 position ± 30 degrees.

Electrical and Basing Connections

The 14CP4 features a coated unipotential cathode. The heater is designed for operation on either AC or DC.

The tube uses the 12N basing configuration. The pin connections, viewed from the bottom of the base, are as follows:

• Pin 1: Heater
• Pin 2: Grid No. 1
• Pin 10: Grid No. 2
• Pin 11: Cathode
• Pin 12: Heater
• Recessed Cap: Anode, Grid No. 3 (internally connected)

Optical and Screen Characteristics

The screen of the 14CP4 utilizes a sulfide-type P4 phosphor. Its optical properties are characterized by:

• Fluorescent Color: White
• Phosphorescent Color: White
• Persistence: Described as short to medium depending on the manufacturer's evaluation criteria.
• Faceplate Type: Spherical, gray neutral-density glass.

Electrostatic and Electromagnetic Characteristics

The 14CP4 employs magnetic methods for both focusing and deflection.

Deflection Angles

The approximate deflection angles of the electron beam are:

• Diagonal: 70 degrees
• Horizontal: 65 degrees
• Vertical: 50 degrees (with some early tentative specifications listing up to 70 degrees)

Direct Interelectrode Capacitances

• Grid No. 1 to All Other Electrodes: 6 µµF
• Cathode to All Other Electrodes: 5 µµF
• External Conductive Coating to Anode: Ranges from a minimum of 750 µµF to a maximum of 2000 µµF (typically around 1500 µµF). When grounded, this external conductive coating serves as a filter capacitor for the high-voltage supply.

Maximum Ratings (Design-Center Values)

The maximum ratings are interpreted according to the standard design-center system, which provides a ten-percent safety factor to withstand variations in line voltage and component tolerances.

Peak Heater-Cathode Voltage

• Heater Negative with Respect to Cathode:
  • During equipment warm-up period (not to exceed 15 seconds): 410 Max Volts
  • After equipment warm-up period: 150 Max Volts
• Heater Positive with Respect to Cathode: 150 Max Volts

Typical Operating Conditions

Under typical operating conditions, the 14CP4 is operated with the following parameters:

• Anode Voltage: 12,000 Volts DC
• Grid-No. 2 Voltage: 300 Volts DC
• Grid-No. 1 Voltage (for visual extinction of focused raster or undeflected spot): -28 to -72 Volts DC (with some operating points extending from -33 to -77 Volts DC)
• Focusing-Coil Current: Approximately 105 mA DC (using a JETEC No. 109 focusing coil positioned 3-1/4 inches from the yoke-reference-line to the center of the air gap) to 115 mA DC
• Ion-Trap Field Intensity: Approximately 23 to 32 Gausses (using a single-field ion-trap magnet adjusted to the optimum position, equivalent to 32 mA through a JETEC No. 117 ion-trap magnet)

Operating and Safety Precautions

X-ray Radiation Shield

If the 14CP4 is operated at voltages in excess of 16,000 volts, x-ray radiation shielding may be necessary to avert the danger of personal injury from prolonged exposure at close range. The protective face-viewing window of the television apparatus may provide a sufficient safeguard. If the radiation measured in contact with this window does not exceed 6.25 milliroentgens per hour, the window will normally provide adequate protection.

Cathode Connection

The cathode of the tube should be returned to one side or to the electrical midtap of the heater transformer winding.

Minimum Operating Voltage

To maintain acceptable brightness and focus quality, the anode voltage should generally not be operated below 10,000 volts.

Technical Summary

The 14CP4 is a 14-inch rectangular glass cathode-ray picture tube featuring magnetic focus and magnetic deflection, a 70-degree diagonal deflection angle, and a gray neutral-density faceplate. Operating typically at an anode voltage of 12,000 V and a Grid-No. 2 voltage of 300 V, it provides a clear, high-contrast white display using a P4 sulfide phosphor. The tube is designed for television receiver service, utilizing a standard 12N basing configuration on a small-shell duodecal 5-pin base, and requires an external single-field ion-trap magnet for proper operation.