19AHP4 — Television Picture Tube

The 19AHP4 is a rectangular glass television picture tube designed for cathode-drive service. It features a short-neck construction, low-voltage electrostatic focusing, and 114-degree magnetic deflection. The tube incorporates an aluminized P4 phosphor screen, a spherical gray filter glass faceplate, and an external conductive coating that acts as a supplementary filter capacitor when grounded. It operates without an ion trap.

Mechanical and Physical Design

The 19AHP4 is built using the J149 bulb envelope with a short neck, minimizing the overall depth of the television receiver. The physical dimensions and mechanical limits of the tube are detailed below:

Screen and Optical Characteristics

The tube features a spherical faceplate made of gray filter glass with a light transmittance of approximately 78% at the center. The screen uses aluminized P4 phosphor. The minimum useful projected screen dimensions are:

• Diagonal: 17-9/16 inches
• Horizontal: 15-1/8 inches
• Vertical: 12 inches
• Total Area: 172 square inches

Deflection Angles

The magnetic deflection system provides wide-angle scanning to cover the rectangular screen area:

• Horizontal Deflection: 103 degrees
• Vertical Deflection: 86 degrees
• Diagonal Deflection: 114 degrees

Base and Mounting Considerations

The tube is equipped with a B7-208 base and uses the 8HR basing configuration. The perimeter of the base wafer is designed to fit inside a 1-3/4 inch diameter circle concentric with the tube axis. To prevent damage to the tube, lateral strains on the base pins must be avoided, and the socket must be connected using flexible leads.

The anode connection is made via a J1-21 recessed small cavity cap. The angular alignment of the anode terminal with respect to pin 4 has a tolerance of 30 degrees.

The yoke reference line is determined by the plane surface of the flared end of a JEDEC Reference-Line Gauge No. 126 when seated on the funnel. For tubes with minimum neck length, a permanent magnet (PM) centering magnet providing 0 to 8 gauss should extend no more than 2-1/8 inches from this reference line.

Heater Ratings and Warm-up

The 19AHP4 has an indirectly heated cathode with the following nominal heater ratings:

• Heater Voltage: 6.3 Volts
• Heater Current (at 6.3 V): 450  5% mA
• Heater Warm-up Time: 11 seconds

The heater warm-up time is specifically defined as the time required for the heater voltage to reach 80% of its rated value when four times the rated voltage (25.2 V) is applied to the heater in series with an external resistance. This series resistance is calculated as three times the rated voltage divided by the rated current:

$\text{Series Resistance} = \frac{3 \times 6.3\text{ V}}{0.45\text{ A}} = 42\ \Omega$

Electrical Connections and Pinout

The 19AHP4 uses the 8HR basing diagram. The pin assignments, viewed from the bottom of the base, are as follows:

Grid No. 1 is internally connected to both Pin 2 and Pin 6.

Interelectrode Capacitances

The internal and external capacitances of the tube are:

• Cathode to all other electrodes (approximate): 5 f
• Grid No. 1 to all other electrodes (approximate): 6 f
• External conductive coating to anode:
  • Maximum: 1500 f
  • Minimum: 1000 f

The external conductive coating forms a supplementary high-voltage filter capacitor with the internal anode coating. This external coating must be properly grounded in the receiver chassis.

Design Maximum System Ratings

The following absolute and design-maximum ratings are established to ensure reliable operation. All voltage values are positive with respect to Grid No. 1 unless otherwise specified.

Electrode Voltages

• Anode Voltage:
  • Maximum: 17,600 Volts
  • Minimum: 12,000 Volts
• Grid No. 4 Voltage (Focusing Electrode): +1100 to -550 Volts
• Grid No. 2 Voltage: 650 Volts
• Cathode Voltage:
  • Maximum Negative DC Value: 0 Volts
  • Maximum Negative Peak Value: 2 Volts
  • Maximum Positive DC Value: 154 Volts
  • Maximum Positive Peak Value: 220 Volts

Note: Operation of the anode below the minimum limit of 12,000 Volts is not recommended, as it causes a significant decrease in picture brilliance and definition.

Heater-Cathode Voltage Limits

• Heater negative with respect to cathode during warm-up ($\le$ 15 seconds): 450 Volts maximum
• Heater negative with respect to cathode after warm-up: 200 Volts maximum
• Heater positive with respect to cathode: 200 Volts maximum

Typical Operating Conditions

Under typical cathode drive service conditions, where voltages are referenced positive with respect to Grid No. 1, the operating parameters are:

Limiting Circuit Values and Safety

To protect the tube from damage due to internal arcing or excessive current, the following circuit resistance limits must be observed:

• Maximum Grid No. 1 Circuit Resistance: 1.5 Megohms
• Minimum Grid No. 2 and Grid No. 4 Circuit Resistance: 10,000 Ohms

The inclusion of a protective series resistance of at least 10,000 Ohms in both the Grid No. 2 and Grid No. 4 circuits is strongly advised to prevent damage to the electrode structures.

X-Ray Radiation Warning

When the 19AHP4 is operated at anode voltages exceeding 16,000 Volts, it can produce very soft X-rays. Depending on the installation and operating voltage, appropriate shielding may be required to limit radiation exposure to safe levels.

Technical Summary

The 19AHP4 is a short-neck, 114-degree magnetic deflection television picture tube featuring low-voltage electrostatic focusing and an aluminized P4 screen. Operating with a nominal 6.3 V, 450 mA heater, the tube is designed for cathode-drive service without an ion trap. Its physical construction utilizes a J149 bulb, a B7-208 base with an 8HR pinout, and an external conductive coating that provides supplementary anode filtering when grounded. With design-maximum ratings supporting anode voltages up to 17,600 V and typical operation at 14,000 V, the 19AHP4 provides a compact, high-performance display solution for television receivers, provided that appropriate protective grid resistances and X-ray shielding are implemented.