19AJP4 — Television Picture Tube

The 19AJP4 is a 19-inch direct-viewed, rectangular glass television picture tube designed primarily for cathode-drive service. It features a low-voltage electrostatic focusing system, 114-degree magnetic deflection, and an aluminized screen. The tube operates with a low Grid No. 2 voltage and does not require an ion-trap magnet.

Mechanical and Physical Construction

The 19AJP4 is built using a rectangular glass bulb (J149A) and has a nominal weight of approximately 13.5 to 14 pounds.

Dimensions and Screen Area

• Overall Length: 11-3/8 ± 1/4 inches
• Neck Length: 4-1/8 ± 1/8 inches
• Neck Diameter: 1-1/8 inches
• Minimum Useful Screen Dimensions:
  • Height: 12 inches
  • Width: 15-1/8 to 15-5/8 inches
  • Diagonal: 17-9/16 inches
• Minimum Useful Screen Area: 172 square inches

Faceplate and Screen Characteristics

The tube features a spherical faceplate made of gray filter glass with a light transmittance of approximately 78% to 79%. The screen is coated with an aluminized P4-Sulfide Type phosphor, which exhibits white fluorescence and short-to-medium persistence.

To prevent electrostatic charge buildup, the tube is equipped with an external conductive coating that must be grounded. The grounding contact area is located near the Reference Line. The high-voltage connection is made via a recessed small cavity cap (JEDEC No. J1-21) on the bulb. The tube can be operated in any position.

Heater and Warm-Up Characteristics

The 19AJP4 utilizes an indirectly heated, coated unipotential cathode. The heater is designed with controlled warm-up characteristics to facilitate series-string operation in television receivers.

• Nominal Heater Voltage: 6.3 V
• Heater Voltage Range (Design-Maximum): 5.8 V to 7.0 V
• Heater Current: 450 mA (with a tolerance of ±5% to ±10%)
• Average Heater Warm-Up Time: 11 seconds

The heater warm-up time is defined as the time required for the heater voltage to reach 80% of its rated value when a voltage equal to four times the rated heater voltage (25.2 V) is applied in series with an external resistance equal to three times the rated heater voltage divided by the rated current. The maximum warm-up period under these conditions is 15 seconds.

Basing and Pin Connections

The 19AJP4 uses a special 6-pin base (JEDEC No. B6-214) with a 7FA basing designation (viewed from the bottom). Base Pin No. 7 aligns with the anode contact (J1-21) within an angular tolerance of 30 degrees.

Depending on the specific manufacturing variant, the pin connections for the 7FA basing are documented with the following configurations:

Configuration 1

• Pin 2: Cathode
• Pin 3: Heater
• Pin 4: Heater
• Pin 5: Grid No. 1
• Pin 6: Grid No. 4 (Focusing Electrode)
• Pin 7: Grid No. 2
• Recessed Cap: Ultor (Grid No. 3, Grid No. 5, Collector)
• External Coating: Grounding contact

Configuration 2

• Pin 1: Heater
• Pin 2: Cathode
• Pin 3: Grid No. 1
• Pin 4: Grid No. 4 / Focus
• Pin 6: Grid No. 4 / Focus
• Pin 7: Grid No. 2
• Pin 8: Heater
• Recessed Cap: Anode
• External Coating: Grounding contact

Configuration 3

• Pin 1: Heater
• Pin 2: Cathode
• Pin 3: Grid No. 1
• Pin 4: Heater
• Pin 5: Grid No. 1
• Pin 6: Grid No. 4 / Focusing Electrode
• Pin 7: Grid No. 2
• Recessed Cap: Anode
• External Coating: Grounding contact

Interelectrode Capacitances

The direct interelectrode capacitances of the tube are approximately:

• Grid No. 1 to all other electrodes: 6 µµF
• Cathode to all other electrodes: 5 µµF
• External conductive coating to anode/ultor: 1400 µµF minimum to 1900 µµF maximum

Electrical Ratings and Operating Limits

The following limits are specified under the Design-Maximum Rating System. Operating the tube beyond these limits can cause permanent damage or severely degrade performance.

• Anode (Ultor) Voltage: 12,000 V DC (minimum) to 19,800 V DC (maximum)
• Grid No. 4 (Focusing Electrode) Voltage: -500 V to +1100 V DC (or -550 V to +1100 V DC)
• Grid No. 2 Voltage: 40 V DC (minimum) to 70 V DC (maximum)
• Cathode Voltage (Positive Bias): 100 V DC (maximum)
• Cathode Voltage (Negative Peak): 0 V
• Grid No. 1 Circuit Resistance: 1.5 MΩ (maximum)

Peak Heater-Cathode Voltage Limits

• Heater negative with respect to cathode:
  • During equipment warm-up (≤ 15 seconds): 410 V maximum
  • After equipment warm-up (steady state): 180 V maximum
• Heater positive with respect to cathode: 180 V maximum

Typical Operating Conditions (Cathode-Drive Service)

In typical cathode-drive applications, all electrode voltages are specified as positive with respect to the Grid No. 1 voltage:

• Anode (Ultor) Voltage: 14,500 V DC
• Grid No. 2 Voltage: 50 V DC
• Grid No. 4 (Focusing) Voltage: 0 to +500 V DC
• Cathode Voltage for Cutoff (Visual Extinction of Focused Raster): 31 to 49 V DC (or 35 to 50 V DC)

Note: Visual extinction of a stationary focused spot requires an increase of approximately 5 V in the cathode voltage.

Focus Modulation

The focus electrode (Grid No. 4) may be modulated to improve overall focus across the entire screen area.

Safety and Operating Considerations

X-ray Radiation Warning

When operated at voltages above 16,000 volts or the maximum rated anode voltage (whichever is less), the 19AJP4 can produce X-rays. Adequate shielding may be necessary to protect against prolonged exposure at close range.

Grounding

The external conductive coating must be securely grounded to the chassis to prevent electrostatic charge buildup and ensure safe operation.