17ATP4A — Electrostatic-Focus Cathode Ray Picture Tube

The 17ATP4A is a direct-view, rectangular glass cathode ray picture tube designed for television applications. It features a nominal diagonal screen size of 17 inches, low-voltage electrostatic focusing, and magnetic deflection. The tube is identical to the 17ATP4 except for the addition of a metal-backed screen.

The 17ATP4A incorporates a spherical, grey-tinted filter faceplate with approximately 66% light transmission at the center, which improves picture contrast under ambient light. The screen utilizes a metal-backed, Sulfide-type P-4 phosphor that produces a white fluorescence and phosphorescence with short persistence. Additional features include an external conductive coating (which must be grounded to form a filter capacitor with the anode) and an external single-field ion trap.

Physical Specifications and Base Configuration

The 17ATP4A is constructed with a rectangular glass envelope. The physical dimensions and mounting requirements are as follows:

• Overall Length: 16 +1/4, -3/8 inches
• Bulb Dimensions: Diagonal 16 5/8 ± 1/8 inches, Width 15 3/8 ± 1/8 inches, Height 12 1/4 ± 1/8 inches
• Minimum Useful Screen Dimensions: Diagonal 15 1/4 inches, Width 14 1/4 inches, Height 11 1/16 inches
• Raster Size: 10 3/4 inches x 14 1/4 inches

Base and Socket Mounting

The tube uses a small shell duodecal 6-pin base (designation B6-63) with a 12L basing arrangement. The bulb contact is a recessed small cavity cap (J1-21), which aligns with pin position #6 within a tolerance of ±30 degrees.

To prevent mechanical stress on the glass envelope, the socket should not be rigidly mounted. Instead, flexible leads must be used to allow free movement of the socket.

Pinout (Basing 12L, Bottom View)

The electrical connections are distributed across the 6-pin base and the recessed anode cap:

Heater and Interelectrode Capacitances

The 17ATP4A utilizes a unipotential cathode with an indirectly heated filament.

• Heater Voltage: 6.3 V
• Heater Current: 0.6 A

Interelectrode Capacitances

The approximate capacitances between the electrodes are:

The capacitance between the external conductive coating and the internal anode serves as a high-voltage filter capacitor when the external coating is properly grounded.

Deflection and Electrostatic Focusing

The tube utilizes magnetic deflection with the following nominal deflection angles:

• Horizontal: 80°
• Vertical: 65°
• Diagonal: 90°

Focusing is achieved electrostatically via Grid #4, which operates at a relatively low voltage. This electrostatic focus design allows the focusing voltage to be adjusted to compensate for variations in anode voltage and beam current.

Operating Ratings and Conditions

The ratings of the 17ATP4A are established under the Design-Maximum system (design center values). Operating the tube within these limits ensures reliable performance and longevity.

Design-Maximum Ratings

• DC Anode, Grid #3, Grid #5 Voltage: Maximum 16,000 V. (Operation up to 17.6 kV absolute is permitted, but shielding for X-ray radiation may be required above 16 kV. The anode voltage should not be operated below 12,000 V to maintain adequate picture brilliance and definition).
• DC Grid #4 (Focusing) Voltage: Positive Maximum 1,000 V, Negative Maximum -500 V (applicable when AC voltage is provided for dynamic focusing).
• DC Grid #2 Voltage: Maximum 500 V.
• Grid #1 Voltage:
  • DC Negative-bias Maximum: 125 V
  • DC Positive-bias Maximum: 0 V
  • Positive-peak Maximum: 2 V
• DC Peak Heater-Cathode Voltage:
  • Heater negative with respect to cathode: Maximum 410 V during warm-up (first 15 seconds or less); Maximum 180 V after warm-up.
  • Heater positive with respect to cathode: Maximum 180 V.
• Grid #1 Circuit Resistance: Maximum 1.5 MΩ.

Typical Operating Conditions

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

An external single-field ion trap magnet adjusted to approximately 37 Gausses is required to prevent ion burn on the phosphor screen.

Technical Summary

The 17ATP4A is an 80-degree horizontal deflection, rectangular glass television picture tube featuring a 17-inch diagonal envelope, low-voltage electrostatic focusing, and a metal-backed Sulfide-type P-4 phosphor screen. It operates with a standard 6.3 V, 0.6 A heater and requires an external single-field ion trap magnet of 37 Gausses for proper operation. With a typical anode operating voltage of 14,000 V and a design-maximum limit of 16,000 V, the tube provides a bright, high-contrast display utilizing its grey filter faceplate. The external conductive coating provides a capacitance of 750 to 1500 μμF to the anode, serving as an integral part of the high-voltage filtering system when grounded.