17DEP4 — Tri-Potential Electrostatic Focus Television Picture Tube

The 17DEP4 is a 17-inch direct-viewed rectangular glass television picture tube designed for use in television receivers. It features a spherical faceplate, an aluminized screen, and a short neck design. The tube utilizes tri-potential electrostatic focusing and 110-degree magnetic deflection, eliminating the need for an external ion trap. An external conductive coating is applied to the bulb to serve as a component of the high-voltage filter capacitor system.

Mechanical Design and Physical Dimensions

The 17DEP4 is constructed with a rectangular glass bulb, designated as either J132 1/2-A or J132 1/2-B. It has a nominal weight of approximately 10 pounds. The physical dimensions of the tube are optimized for compact receiver designs, featuring a short neck length of 3 5/16 ± 1/8 inches and an overall length of 10 7/16 ± 1/4 inches.

The screen is coated with an aluminized P4 phosphor that exhibits white fluorescence with short-to-medium persistence. The faceplate is made of gray filter glass with a light transmittance of approximately 77% to improve picture contrast under ambient light.

The minimum useful screen dimensions and area are:

• Height: 11 11/16 inches
• Width: 14 3/4 inches
• Diagonal: 15 3/4 inches
• Total Area: 155 square inches

The tube's design accommodates wide-angle deflection to minimize cabinet depth, with the following deflection angles:

• Horizontal: 105°
• Diagonal: 110°
• Vertical: 87°

Electrical connection to the high-voltage anode is made via a recessed small cavity cap (J1-21) located on the bulb cone. The tube uses a B7-208 base.

Heater and Electrical Characteristics

The 17DEP4 is equipped with an indirectly heated cathode designed for series or parallel heater strings. The heater has a controlled warm-up time to ensure compatibility with series-connected receiver designs.

The heater warm-up time is defined as the time required for the heater voltage to reach 80% of its rated value under a specified series resistance test condition.

Direct Interelectrode Capacitances

The direct interelectrode capacitances of the tube, measured without an external shield, are approximately:

• Cathode to all other electrodes: 3.5 µµf
• Grid No. 1 to all other electrodes: 4 µµf
• External conductive coating to anode: 1400 µµf maximum, 900 µµf minimum

The capacitance between the external conductive coating and the internal anode serves as a filter capacitor for the high-voltage power supply.

Pinout and Base Connections

The 17DEP4 uses the 8JN basing arrangement. The base pins are configured as follows:

• Pin 1: Grid No. 1 / Heater
• Pin 2: Grid No. 3 (Focusing Electrode)
• Pin 6: Internal Connection (IC)
• Pin 7: Cathode
• Pin 8: Heater

Pins 6 and 7 are located on the same side of the neck as the anode contact cap. The internal connection on Pin 6 should not be used for external circuit connections.

Typical Operating Conditions (Grid Drive Service)

Under typical operating conditions in grid drive service, the electrostatic focusing electrode (Grid No. 3) is operated at a low-to-moderate positive potential relative to the cathode, allowing for a wide range of focus voltage adjustment.

• Anode Voltage: 14,000 V dc
• Grid No. 3 Voltage for Focus: 0 to +400 V dc
• Grid No. 2 Voltage: 500 V dc (a minimum of 400 V is recommended to maintain adequate brightness and resolution)
• Grid No. 1 Voltage for Cutoff: −43 to −72 V dc

The cutoff voltage is defined as the value required for the visual extinction of a focused raster. For stationary spot extinction, a bias of approximately 5 V more negative is required.

Maximum Circuit Values

To prevent damage to the tube and maintain bias stability, the maximum resistance in the Grid No. 1 circuit must be limited:

• Grid No. 1 Circuit Resistance: 1.5 Megohms maximum

Absolute Maximum Ratings

The absolute maximum ratings represent the limiting values of operation beyond which the serviceability or safety of the tube may be impaired. All voltages are specified with respect to the cathode unless otherwise noted.

Electrode Voltages

• Anode Voltage: 17,600 V dc
• Grid No. 3 Voltage (Focusing Electrode): 700 V dc
• Grid No. 2 Voltage: 700 V dc
• Grid No. 1 Voltage:
  • Negative Bias: 154 V dc
  • Negative Peak: 220 V
  • Positive Bias: 0 V dc
  • Positive Peak: 2 V

Heater-Cathode Voltage Limits

The peak heater-cathode voltage ratings vary depending on the operating state and the polarity of the heater relative to the cathode:

• Heater negative to cathode:
  • During warm-up (≤ 15 seconds): 450 V peak
  • After warm-up: 200 V peak
• Heater positive to cathode:
  • 200 V peak

Technical Summary

The 17DEP4 is a 17-inch rectangular glass television picture tube featuring a short neck, 110-degree magnetic deflection, and tri-potential electrostatic focusing. Operating at a typical anode voltage of 14,000 V, it provides a bright, high-resolution display on its 155-square-inch aluminized P4 screen. Its low-voltage heater (2.35 V, 0.600 A) features a controlled 11-second warm-up time, making it suitable for series-string television chassis. With its integrated external conductive coating and electrostatic focus design, the 17DEP4 eliminates the need for external ion traps and complex focusing magnets, simplifying receiver circuitry and reducing cabinet depth.