17JP4 — Rectangular Television Picture Tube

The 17JP4 is a 17-inch direct-view rectangular glass cathode ray tube designed specifically for television receiver applications. It features a unipotential cathode, magnetic deflection, magnetic focusing, and an external single-field ion trap. To improve picture contrast under ambient light, the tube is constructed with a neutral density gray filter glass faceplate. It also incorporates an external conductive coating that must be grounded during operation.

Mechanical and Optical Specifications

The 17JP4 is built with a rectangular glass envelope that maximizes the useful screen area relative to its overall physical size.

Physical Dimensions

• Overall Length: 19 3/16 ± 3/8 inches
• Greatest Bulb Dimensions:
  • Diagonal: 16 5/8 ± 1/8 inches
  • Width: 15 3/8 ± 1/8 inches
  • Height: 12 9/32 inches (with a tolerance of +1/8 to -7/32 inches)
• Minimum Useful Screen Dimensions:
  • Diagonal: 15 1/2 inches
  • Width: 14 1/4 inches
  • Height: 10 3/4 inches
• Raster Size: Nominally 10 3/8 x 14 1/8 inches to 10 3/4 x 14 1/4 inches

Optical Characteristics

The screen utilizes a No. 4 (P4) sulfide-type phosphor which produces a white fluorescence and white phosphorescence with medium persistence. The faceplate is made of gray filter glass, providing approximately 66% light transmission at the center to enhance contrast by reducing the reflection of ambient room light.

Deflection Angles

The tube's electron gun and bulb shape are designed for the following approximate deflection angles:

• Horizontal: 65° to 66°
• Vertical: 50°
• Diagonal: 70°

Electrical Connections and Basing

The 17JP4 uses a small shell duodecal 5-pin base (B5-57) with a 12N basing arrangement. High voltage is supplied to the anode via a recessed small cavity cap (J1-21) located on the bulb cone. The anode contact is aligned with pin position No. 6 within a tolerance of ± 30 degrees.

Pinout Configuration

The electrical connections viewed from the bottom of the base are as follows:

Interelectrode Capacitances

The approximate direct interelectrode capacitances of the tube are:

• Cathode to all other electrodes: 5 μμf
• Grid No. 1 to all other electrodes: 6 μμf
• External conductive coating to collector (anode): 500 μμf (minimum) to 750 μμf (maximum)

The external conductive coating must be connected to a reliable electrical ground to complete the high-voltage return path and minimize electrical noise.

Electrical Ratings and Operating Conditions

The operating limits and typical parameters of the 17JP4 are specified under the Design Center rating system.

Maximum Ratings

These ratings represent the absolute limits within which the tube must be operated to ensure reliability and longevity:

• Heater Voltage: 6.3 V
• Heater Current: 0.6 A
• Maximum DC Grid No. 3 & Collector (Anode) Voltage: 18,000 V
• Maximum DC Grid No. 2 Voltage: 410 V
• Maximum Grid No. 1 Voltage:
  • DC Negative-Bias Value: 125 V
  • DC Positive-Bias Value: 0 V
  • Positive-Peak Value: 2 V
• Maximum DC 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): 150 V
  • Heater positive with respect to cathode: 150 V

Typical Operating Conditions

For optimal performance, including adequate picture brilliance and focus definition, the following typical operating conditions are recommended:

• DC Grid No. 3 & Collector (Anode) Voltage: 16,000 V (Operation below this value is generally not recommended as brilliance and definition decrease)
• DC Grid No. 2 Voltage: 300 V
• DC Grid No. 1 Voltage (for visual extinction of undeflected focused spot): -33 V to -77 V
• DC Focusing Coil Current: 100 mA to 110 mA (with a tolerance of ± 10%). This is measured using a standard JETEC focusing coil No. 109 or equivalent, positioned 3.0 inches from the reference line to the center of the coil's air gap. The Grid No. 1 bias and video signal are adjusted to achieve a highlight brightness of 20 to 30 foot-lamberts on a 10 3/4 x 14 1/4 inch picture area.
• Ion Trap Magnet Field Strength: 45 to 50 Gausses (using standard single-field magnet coil No. 111 or equivalent).

Circuit Values

• Maximum Grid No. 1 Circuit Resistance: 1.5 Megohms

Safety and Radiation Considerations

When operating the 17JP4, safety precautions must be observed regarding high voltage and potential radiation. If the tube is operated at or near its maximum rated anode voltage, or above 16,000 V (whichever is less), it can produce X-rays. Adequate shielding may be necessary in the receiver cabinet design to protect users from prolonged exposure at close range.

Technical Summary

The 17JP4 is a specialized 17-inch rectangular glass television picture tube utilizing magnetic deflection and focus. Operating with a nominal 6.3 V, 0.6 A heater, it provides a high-resolution monochrome display on a white-emitting P4 phosphor screen. Its design incorporates a neutral density faceplate with 66% light transmission to maintain contrast under ambient light, and an external conductive coating that acts as a filter capacitor when grounded. With a maximum anode rating of 18,000 V and a typical operating point of 16,000 V, the 17JP4 delivers bright, sharply focused television images when paired with a standard 109 focusing coil and a 45 to 50 Gauss single-field ion trap magnet.