16ABP4 — Electrostatic-Focus Television Picture Tube

The 16ABP4 is a direct-view cathode-ray picture tube designed specifically for television receiver applications. It features a rectangular glass construction, electrostatic focusing, and magnetic deflection. The design incorporates a grey filter faceplate to enhance picture contrast under ambient illumination, an external conductive bulb coating, and requires an external single-field ion trap magnet for proper operation.

Mechanical Design and Physical Dimensions

The 16ABP4 is constructed with a rectangular glass bulb envelope. Its physical dimensions and screen characteristics are highly specified to ensure proper mounting and alignment within television cabinets:

• Overall Length: 18 3/4 ± 3/8 inches
• Greatest Bulb Dimensions:
  • Diagonal: 16 1/8 ± 1/8 inches
  • Width: 14 3/4 ± 1/8 inches
  • Height: 11 1/8 ± 1/8 inches
• Minimum Useful Screen Dimensions:
  • Diagonal: 14 7/8 inches
  • Width: 13 1/2 inches
  • Height: 10 1/2 inches
• Raster Size: 13 1/2 x 10 1/2 inches

Bulb Connections and Alignment

The electrical connection to the high-voltage anode is made via a recessed small cavity cap (designated J1-21). The tube base is a small shell duodecal 5-pin base (designated B5-57), which conforms to the 12N basing arrangement.

To ensure proper orientation of the internal electron gun relative to the external deflection yoke and ion trap magnet, the J1-21 anode contact is aligned with pin position #6 on the base within a tolerance of ±10 degrees. A specific region on the neck must be kept clear for the installation of the external ion trap magnet.

Electrical and Optical Characteristics

The 16ABP4 utilizes a unipotential cathode with an indirectly heated filament.

Heater and Cathode Requirements

The heater is designed to operate under standard television receiver power supply conditions:

The cathode must be electrically returned to one side or to the center-tap of the heater transformer winding to minimize hum and potential differences.

Interelectrode Capacitances

The tube exhibits the following approximate direct interelectrode capacitances:

• Cathode to all other electrodes: 5.0 µµF
• Grid No. 1 to all other electrodes: 6.5 µµF
• External conductive coating to anode: 750 µµF (minimum) to 1,500 µµF (maximum)

The external conductive coating acts as a capacitor in conjunction with the internal anode coating, which can be utilized as a high-voltage filter capacitor when the external coating is grounded.

Optical Specifications

The faceplate of the 16ABP4 is designed to optimize image quality:

• Phosphor Type: No. 4
• Fluorescent Color: White
• Phosphorescent Color: White
• Persistence: Medium
• Faceplate Light Transmission: Approximately 66% at the center, achieved via a grey filter glass to reduce reflections and enhance contrast.

Ratings and Operating Conditions

The ratings for the 16ABP4 are established under the Design Center system. Operating the tube beyond these limits may impair performance or cause permanent damage.

Maximum Ratings

• DC Anode, Grid No. 3, and Grid No. 5 Voltage: 16,000 V
• DC Grid No. 2 Voltage: 500 V
• Grid No. 1 Voltage:
  • DC Negative-Bias Value: 125 V
  • DC Positive-Bias Value: 0 V
  • Positive-Peak Value: 2 V
• 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): 180 V
  • Heater positive with respect to cathode: 180 V

Typical Operating Conditions

Under typical operating conditions, the tube is set up with the following parameters:

• DC Anode, Grid No. 3, and Grid No. 5 Voltage: 14,000 V
• DC Grid No. 2 Voltage: 300 V
• DC Grid No. 1 Voltage (for visual extinction of an undeflected focused spot): -33 V to -77 V
• DC Ion Trap Current (using standard coil #111): Approximately 75 mA (with a tolerance of ±50%)

Circuit Constraints

To prevent grid emission and bias instability, the maximum resistance in the Grid No. 1 circuit must not exceed 1.5 Megohms.

Pinout and Electrode Connections

The 12N basing diagram, viewed from the bottom of the tube base, provides the following pin connections:

The electrostatic focusing is achieved internally, with Grid No. 3 and Grid No. 5 connected to the high-voltage anode terminal (recessed small cavity cap). Magnetic deflection is applied externally via a yoke around the neck of the tube, providing an approximate diagonal deflection angle of 70 degrees.