17EAP4 — Electrostatic Focus Picture Tube

The 17EAP4 is a rectangular glass cathode-ray picture tube designed for television receiver applications. It features automatic electrostatic focusing, magnetic deflection, and an aluminized screen. The tube is designed to eliminate ion spot blemishes through the use of a single external magnetic field ion trap.

Physical and Mechanical Construction

The 17EAP4 is constructed with a rectangular glass envelope (Bulb No. J133B1/D1) and an aluminized screen utilizing No. 4 phosphor. The screen provides a minimum useful projected area of 150 square inches, with a center light transmittance of approximately 74%.

Mechanical Dimensions

The physical dimensions of the tube are characterized by the following measurements:

• Overall Length: 19 1/4 ± 3/8 inches
• Neck Length: 7 1/2 ± 3/16 inches
• Greatest Diagonal Dimension: 16 5/8 ± 1/8 inches
• Greatest Width: 15 3/8 ± 1/8 inches
• Greatest Height: 12 1/4 ± 1/8 inches
• Minimum Useful Screen Diagonal (Projected): 15 9/16 inches
• Minimum Useful Screen Horizontal Axis (Projected): 14 5/16 inches
• Minimum Useful Screen Vertical Axis (Projected): 11 1/8 inches

Deflection and Focusing

The tube operates with magnetic deflection, offering the following approximate deflection angles:

• Horizontal: 65 degrees
• Vertical: 50 degrees
• Diagonal: 70 degrees

Focusing is achieved automatically via an electrostatic focus design. The Grid No. 4 ($G_4$) focus electrode is internally connected to the filament lead on Pin 1, which eliminates the requirement for an external focus voltage connection.

Heater, Base, and Pinout

The 17EAP4 utilizes an indirectly heated filament and a standard base configuration. The external conductive coating of the bulb must be grounded during operation.

Heater Ratings

• Nominal Heater Voltage: 6.3 V
• Nominal Heater Current: 0.6 A (subject to a ±10% tolerance)

Base and Basing Configuration

The tube features a B5-57 Small Shell Duodecal 5-Pin Base and utilizes the 12AT basing arrangement. The high-voltage anode connection is made via a J1-21 anode cavity cap located on the bulb envelope.

Electrical Characteristics and Capacitances

The electrical interface of the 17EAP4 includes capacitance between the external conductive coating and the internal anode structure:

• External Conductive Coating to Anode Capacitance (Maximum): 1500 µµF (pF)
• External Conductive Coating to Anode Capacitance (Minimum): 1000 µµF (pF)

Operating Conditions and Ratings

The operating limits of the 17EAP4 are defined under the Design Maximum System. All voltages are positive and measured with respect to the cathode unless otherwise specified.

Design-Maximum Ratings

• Anode Voltage: 17,600 V max.
• Grid No. 2 Voltage: 550 V max.
• Grid No. 1 Voltage:
  • Maximum Negative DC Value: 155 V
  • Maximum Negative Peak Value: 220 V
  • Maximum Positive DC Value: 0 V
  • Maximum Positive Peak Value: 2 V
• Heater Voltage Range: 5.6 V to 7.0 V
• Maximum 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 (Grid Drive Service)

Under typical grid drive operating conditions, the tube is configured with the following parameters:

• Anode Voltage: 12,000 V DC
• Grid No. 2 Voltage: 300 V DC
• Grid No. 1 Voltage (for visual extinction of focused raster): -28 V to -72 V DC
• Ion Trap Current: 40 ± 50% mA DC (using JEDEC Coil #RMA111)

To achieve proper ion trap alignment and maximum screen brightness, the external ion trap magnet must be positioned with the trailing edge of its pole pieces directly over the gap between Grid No. 1 and Grid No. 2.

Operating and Safety Notes

Socket Mounting

The socket for the 17EAP4 must not be rigidly mounted. To prevent mechanical strain on the glass neck and base pins, the socket must be connected via flexible leads and allowed to move freely.

X-ray Radiation Warning

When the 17EAP4 is operated at anode voltages exceeding 16,000 Volts, it can produce X-rays. Personal safety may require the installation of appropriate radiation shielding around the tube.

Technical Summary

The 17EAP4 is a 17-inch class rectangular television picture tube featuring automatic electrostatic focusing ($G_4$ tied internally to Pin 1) and magnetic deflection (70-degree diagonal). It operates with a 6.3 V, 0.6 A heater and is housed in a J133B1/D1 glass envelope with a B5-57 Small Shell Duodecal 5-pin base. Under typical grid drive service, it operates at an anode voltage of 12,000 V DC (with a design-maximum limit of 17,600 V) and requires an external single-field ion trap magnet for proper raster alignment and blemish prevention.