19DP4 — Direct-View Picture Tube

The 19DP4 is a direct-view, round glass picture tube designed primarily for television receiver applications. It features a unipotential cathode, magnetic focusing, and magnetic deflection. The tube is equipped with an external conductive coating and requires an external single-field ion trap for proper operation.

A closely related variant, the 19DP4A, shares the same electrical and mechanical characteristics but incorporates a grey filter faceplate providing approximately 70% light transmission at the center, whereas the standard 19DP4 features a clear glass faceplate.

Mechanical Specifications and Basing

The 19DP4 is constructed with a round glass bulb and a small shell duodecal 5-pin base (designation B5-57), utilizing the 12N basing arrangement. The high-voltage anode connection is made via a recessed small cavity cap (J1-21) located on the side of the bulb.

Physical Dimensions

• Overall Length: 21-1/2" ± 3/8"
• Greatest Bulb Diameter: 18-7/8" ± 1/8"
• Minimum Useful Screen Diameter: 17-3/8"
• Typical Raster Size: 11-3/4" x 15-3/4"
• Bulb Contact Alignment: The J1-21 anode contact aligns with pin position #3 within a tolerance of ±10 degrees.

Pin Connections

Viewed from the bottom of the base, the 12N pinout provides the following connections:

Optical and Electrical Characteristics

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

Deflection and Capacitance

• Focusing Method: Magnetic
• Deflecting Method: Magnetic
• Deflection Angle (Approximate): 56°
• Direct Interelectrode Capacitances: The capacitance from the external conductive coating to the anode ranges from a minimum of 750 µµF to a maximum of 2500 µµF.

Heater Ratings

The heater is designed for a nominal voltage of 6.3 V and draws a nominal current of 0.6 A. The calculated nominal power consumption of the heater is:

$\text{Power} = 6.3\text{ V} \times 0.6\text{ A} = 3.78\text{ W}$

Maximum Ratings (Design Center Values)

The operating limits of the 19DP4 must be maintained within the specified Design Center Values to ensure reliable performance and longevity:

• Maximum DC Anode Voltage: 17,000 V
• Maximum DC Grid No. 2 Voltage: 410 V
• Maximum Grid No. 1 Voltage:
  • DC negative-bias value: 125 V
  • DC positive-bias value: 0 V
  • Positive-peak value: 2 V
• Maximum DC Peak Heater-Cathode Voltage:
  • Heater negative with respect to cathode during warm-up (≤ 15 seconds): 410 V
  • Heater negative with respect to cathode after warm-up: 125 V
  • Heater positive with respect to cathode: 125 V

Typical Operating Conditions and Circuit Values

Under typical operating conditions, the tube is configured with the following parameters to achieve a highlight brightness of 25 foot-lamberts on the standard 11-3/4" x 15-3/4" raster:

• DC Anode Voltage: 13,000 V
• DC Grid No. 2 Voltage: 250 V
• DC Grid No. 1 Voltage (for visual extinction of undeflected focused spot): -26 V to -63 V
• DC Focusing Coil Current: Approximately 146 mA, using a standard focus coil (such as focus coil #109 or equivalent) positioned with the air gap center 3.25" from the reference line.
• DC Ion Trap Current: Approximately 75 mA when using a standard single-field ion trap coil. Based on the specified ±50% tolerance, the calculated operating range for the ion trap current is 37.5 mA to 112.5 mA.
• Maximum Grid No. 1 Circuit Resistance: 1.5 MΩ

Technical Summary

The 19DP4 is a 56-degree magnetic-deflection, magnetic-focus round glass television picture tube. It operates with a 6.3 V, 0.6 A heater and features a white-emitting Phosphor No. 4 screen. The tube is characterized by its 12N duodecal basing, requiring an external single-field ion trap and an external conductive coating that provides up to 2500 µµF of capacitance to the anode. With a maximum anode rating of 17,000 V and typical operation at 13,000 V, the 19DP4 and its grey-filtered counterpart, the 19DP4A, served as standard direct-view displays in early television receiver designs.