17CP4 — Rectangular Metal-Cone Cathode Ray Picture Tube

The 17CP4 is a 17-inch rectangular, metal-cone, direct-view cathode ray picture tube designed for television applications. It features magnetic focus and magnetic deflection, utilizing an external single-field ion-trap magnet to prevent screen damage. The tube incorporates a unipotential cathode and a high-efficiency sulfide-type phosphor screen that produces a white fluorescent and phosphorescent display.

Designations and Physical Construction

The 17CP4 family includes two closely related variants:

• 17CP4: Features a spherical, gray, frosted faceplate that reduces specular reflection of ambient light (limited to a maximum of 1.5%) and enhances picture contrast.
• 17CP4A: Identical to the 17CP4 but utilizes an unfrosted faceplate.

The physical envelope of the tube is constructed with a lightweight metal cone. Because the metal cone operates at high voltage, it must be properly insulated to withstand the maximum applied anode voltage. The faceplate is made of filter glass with a light transmission of approximately 65% to 66% at the center.

The mechanical dimensions of the tube are as follows:

• Overall Length: 19 inches
• Greatest Bulb Dimensions:
  • Diagonal: 16 13/16 ± 3/16 inches
  • Width: 15 15/16 ± 1/8 inches
  • Height: 12 1/4 ± 1/8 inches
• Minimum Useful Screen Dimensions:
  • Width: 14 5/8 inches (or 14 3/8 inches in some configurations)
  • Height: 11 inches (or 10 11/16 inches in some configurations)
  • Raster/Picture Size: 14 5/8" x 11" or 14 3/4" x 10 11/16"
• Net Weight: Approximately 10 lbs.

The tube provides wide deflection angles to cover the rectangular screen area:

• Horizontal Deflection Angle: 66°
• Vertical Deflection Angle: 50°
• Diagonal Deflection Angle: 70°

Electrical Specifications and Base Connections

The 17CP4 uses a small-shell Duodecal 5-pin base (JETEC No. B5-57) with a 12D basing designation. The electrical connections are made through the base pins and a metal shell lip, which serves as the anode contact. The anode and Grid No. 3 are connected internally.

Depending on the specific manufacturing standard, the base alignment is specified as either Pin No. 6 aligning with the horizontal picture axis within ±10 degrees, or Pin No. 3 aligning with the horizontal picture axis within ±30 degrees.

Pin Connections (Bottom View)

• Pin 1: Heater
• Pin 2: Grid No. 1
• Pin 10: Grid No. 2
• Pin 11: Cathode
• Pin 12: Heater
• Metal Shell Lip / Cone Lip: Anode

Interelectrode Capacitances

• Cathode to all other electrodes: Approximately 5 µµF
• Grid No. 1 to all other electrodes: Approximately 6 µµF

Absolute and Design-Center Ratings

The operating limits of the 17CP4 must be strictly observed to ensure reliable operation and prevent damage to the tube:

• Heater Voltage: 6.3 V
• Heater Current: 0.6 A (with a tolerance of ±10%)
• Maximum DC Anode Voltage: 16,000 V (The product of the anode voltage and the average anode current must be limited to 6 W)
• 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: 180 V
  • Heater positive with respect to cathode: 180 V
• Maximum Grid No. 1 Circuit Resistance: 1.5 Megohms

Typical Operating Conditions and Adjustments

The 17CP4 can be operated under slightly different typical conditions depending on the desired brightness and focus characteristics. Brilliance, focus quality, and definition decrease with decreasing anode voltage, and the anode voltage should not be operated below 12,000 V.

Operating Point Examples

Two typical operating configurations are documented:

Focusing and Ion-Trap Adjustments

For Configuration A, the focusing coil current of 96 ± 6% mA is specified for a standard focus coil No. 109 or equivalent. This is measured with the combined Grid No. 1 bias and video signal adjusted to produce a highlight brightness of 30 foot-lamberts on a 10 11/16" x 14 3/8" picture size, with the focus coil air gap center positioned 3.0 inches from the reference line. The ion-trap current is approximately 70 mA using a standard coil No. 111, establishing a field strength of 45 Gausses.

For Configuration B, the focusing coil current of 112 mA DC is specified for a RETMA focusing coil No. 109, with a 3 1/2" distance from the yoke reference line to the center of the air gap. The ion-trap field intensity of 37 Gausses is achieved by adjusting a single-field ion-trap magnet to its optimum position, which is equivalent to 37 mA through a RETMA magnet No. 117.

Technical Summary

The 17CP4 is a high-voltage, rectangular, metal-cone television picture tube featuring a 17-inch screen, magnetic focus, and magnetic deflection. It operates with a nominal 6.3 V, 0.6 A heater and is rated for a maximum DC anode voltage of 16,000 V. The tube utilizes a Sulfide Type No. 4 (P4) white phosphor screen with medium/short persistence. The 17CP4 variant features a frosted faceplate to minimize ambient reflections, while the 17CP4A variant uses an unfrosted faceplate. With its standard Duodecal 5-pin base and robust design-center ratings, the 17CP4 provides reliable direct-view imaging for vintage television applications.