14RP4A — Electrostatic-Focus Television Picture Tube

The 14RP4A is a 14-inch, direct-viewed, rectangular glass television picture tube. It features a spherical faceplate, magnetic deflection, electrostatic focusing, and an external conductive coating. The primary distinction between the 14RP4A and its sister designation, the 14RP4, lies in the screen construction: while the standard 14RP4 uses a conventional P4 phosphor screen, the 14RP4A is equipped with an aluminized P4 screen for enhanced brightness and performance.

Mechanical Construction and Physical Characteristics

The 14RP4A is designed with a rectangular glass envelope and a spherical faceplate made of gray filter glass. This filter glass provides a light transmittance of approximately 78%, which improves picture contrast under ambient room lighting.

Screen Dimensions and Area

• Minimum Useful Screen Dimensions: 12-1/16 x 9-1/2 inches
• Minimum Useful Screen Area: 104 square inches

Physical Connections and Alignment

• Bulb Contact: Recessed small cavity cap (J1-21)
• Base: Small shell duodecal 6-pin (B6-63)
• Basing Configuration: 12L
• Weight: Approximately 8.5 pounds

The tube's physical layout requires specific alignment during installation. The reference line of the tube is determined by the plane C-C' of a standard JETEC No. 116 reference line gauge when the gauge is resting on the glass cone. Base pin number 6 is aligned with the anode contact terminal (J1-21) within a tolerance of 30 degrees. Additionally, a 2" x 2" contact area for the external conductive coating is located 90 degrees counterclockwise from the anode contact, as viewed from the base end of the tube.

Electrical Specifications and Heater Characteristics

The 14RP4A utilizes an indirectly heated cathode. The heater is designed to operate under standard television receiver power conditions, featuring a controlled warm-up time to ensure compatibility with series-string heater circuits.

Heater Ratings

• Heater Voltage: 6.3 Volts
• Heater Current: 0.6 ± 5% Ampere
• Heater Warm-up Time: 11 seconds

The heater warm-up time is defined as the time required for the voltage across the heater terminals to increase to 5.0 volts when tested in a standard JETEC test circuit with a source voltage of 25 volts and a series resistance of 31.5 ohms.

Direct Interelectrode Capacitances

The direct interelectrode capacitances of the tube are approximately:

• Cathode to All Other Electrodes: 5 pF
• Grid No. 1 to All Other Electrodes: 6 pF
• External Conductive Coating to Anode: 1200 pF maximum, 800 pF minimum

The external conductive coating must be grounded during operation to serve as a high-voltage filter capacitor in conjunction with the internal anode coating.

Typical Operating Conditions and Focus Requirements

Under typical operating conditions, the 14RP4A operates with a nominal anode voltage of 12,000 Volts DC. The electrostatic focusing design allows the focus electrode (Grid No. 4) to be operated at or near ground potential, or adjusted within a range to achieve optimal spot sharpness.

Typical Operating Points

• Anode Voltage: 12,000 Volts DC
• Grid No. 4 Voltage (Focusing Electrode): -50 to +350 Volts DC
• Grid No. 2 Voltage: 300 Volts DC
• Grid No. 1 Voltage (for Cutoff): -26 to -70 Volts DC

Visual extinction of the focused raster occurs within the Grid No. 1 voltage range of -26 to -70 Volts. However, complete extinction of a stationary focused spot requires that the Grid No. 1 bias be made approximately 5 volts more negative than the raster cutoff value.

Ion Trap Magnet Requirements

The 14RP4A requires an external, single-field ion trap magnet to prevent ion burn on the phosphor screen.

• Electromagnetic Ion Trap: An average current of 35 mA DC is typical when using a JETEC Ion Trap Magnet No. 117, with its pole pieces centered over Grid No. 2 on the mount and rotated to achieve maximum screen brightness.
• Permanent Magnet (PM) Ion Trap: A permanent magnet ion trap must have a minimum field strength of 40 Gausses (assuming a typical PM ion trap magnet with a field strength tolerance of ±3 gausses).

Absolute Maximum Ratings and Safety

The operating limits of the 14RP4A are defined under the Absolute Maximum system. Operating the tube beyond these limits can result in permanent damage or severely degraded performance.

Maximum Voltage and Resistance Ratings

• Anode Voltage: 15,400 Volts DC
• Grid No. 4 Voltage (Focusing Electrode): -550 to +550 Volts DC
• Grid No. 2 Voltage: 440 Volts DC
• Grid No. 1 Voltage:
  • Negative Bias Value: 120 Volts DC
  • Negative Peak Value: 175 Volts
  • Positive Bias Value: 0 Volts DC
  • Positive Peak Value: 2 Volts
• Peak Heater-Cathode Voltage:
  • Heater Negative with Respect to Cathode: 200 Volts
  • Heater Positive with Respect to Cathode: 200 Volts
• Grid No. 1 Circuit Resistance: 1.5 Megohms maximum

X-ray Radiation Warning

Because the 14RP4A operates at high anode voltages, it is capable of generating X-rays. X-ray radiation shielding may be necessary to protect against the danger of personal injury from prolonged exposure at close range if the tube is operated at voltages higher than 16,000 volts or the maximum rated anode voltage of 15,400 Volts, whichever is less.

Technical Summary

The 14RP4A is a 14-inch rectangular television picture tube featuring electrostatic focusing, magnetic deflection (85-degree horizontal and 90-degree diagonal deflection angles), and an aluminized P4 white-emitting phosphor screen. Operating with a 6.3 V, 0.6 A heater, the tube is designed for reliable performance in television receivers. It requires an external single-field ion trap magnet and a grounded external conductive coating. With a maximum anode rating of 15,400 Volts DC and a typical operating anode voltage of 12,000 Volts DC, the 14RP4A provides a compact, high-contrast display solution, while incorporating safety considerations for high-voltage operation and potential X-ray emission.