17CEP4 — Rectangular Television Picture Tube

A short-neck, rectangular glass picture tube featuring electrostatic focus, magnetic deflection, and an aluminized screen, designed for direct-view television receiver applications.

Overview

The 17CEP4 (also written as 17CE P4) is a rectangular glass, direct-view picture tube manufactured by Thomas Electronics, Inc. and introduced in early 1957. It features a short neck, a spherical lightweight face, and a short straight electron gun that does not require an external ion trap magnet. The tube utilizes electrostatic focusing and magnetic deflection, and incorporates a metal-backed (aluminized) screen to enhance brightness and contrast.

Physical and Optical Characteristics

The 17CEP4 is constructed with a gray filter glass faceplate having approximately 79% light transmission, which improves picture contrast under ambient light. The screen uses a P4 aluminized phosphor, which exhibits white fluorescence and medium persistence.

The physical dimensions and deflection angles of the tube are optimized for compact television cabinet designs:

• Deflection Angles (Approximate): Diagonal 90°, Horizontal 85°, Vertical 68°
• Minimum Useful Screen Dimensions: 14-3/4 inches by 11-11/16 inches
• Minimum Useful Screen Area: 155 square inches

The envelope features a Recessed Small Cavity Cap (J1-21) for the anode connection, which is aligned with Pin Position No. 6 within a tolerance of ±30 degrees.

Electrical Connections and Pinout

The tube uses a Small Shell Duodecal 6-pin base (JETEC B6-63) with a 12L electrostatic basing designation. The pin connections, viewed from the bottom of the base, are as follows:

Heater Ratings

The heater is designed for a nominal supply voltage of 6.3 Volts and draws a nominal current of 0.45 Ampere (450 mA) with a tolerance of ±10%.

Interelectrode Capacitances

The approximate capacitances between the electrodes are:

• Cathode to all other electrodes: 5 pF
• Grid No. 1 to all other electrodes: 6 pF
• External conductive coating to anode: 1500 pF maximum, 1200 pF minimum

Operating Conditions and Electrical Characteristics

The 17CEP4 is designed to operate under specific recommended conditions to achieve optimal focus and raster quality.

Recommended Operating Points

• Anode Voltage: 14,000 Volts DC
• Grid No. 4 (Focusing Electrode) Voltage: -50 to +350 Volts DC (for focus with an anode current of 100 µA and a 14-3/4" x 11-11/16" raster)
• Grid No. 2 Voltage: 300 Volts DC
• Grid No. 1 Voltage (for visual extinction of focused raster): -28 to -72 Volts DC (extinction of a stationary focused spot requires approximately 5 Volts more negative bias)

Circuit Values

• Grid No. 1 Circuit Resistance: 1.5 Megohms maximum

Absolute Maximum Ratings

The following design-center maximum ratings represent the absolute limits within which the tube must be operated to ensure reliability and safety:

• Anode Voltage: 16,000 Volts DC maximum
• Grid No. 4 Voltage (Focusing Electrode): -500 to +1000 Volts DC maximum
• Grid No. 2 Voltage: 500 Volts DC maximum
• Grid No. 1 Voltage:
  • Negative Bias Value: 140 Volts DC maximum
  • Positive Bias Value: 0 Volts DC maximum
  • Positive Peak Value: 2 Volts maximum
• Peak Heater-Cathode Voltage:
  • Heater negative with respect to cathode (during warm-up ≤ 15 seconds): 410 Volts DC maximum
  • Heater negative with respect to cathode (after warm-up): 180 Volts DC maximum
  • Heater positive with respect to cathode: 180 Volts DC maximum

Operational and Safety Considerations

When integrating the 17CEP4 into television receiver circuits, several operational guidelines must be followed:

Cathode Return

The cathode should be returned directly to one side of the heater transformer winding or to its center tap.

X-Ray Radiation Warning

If the tube is operated at voltages exceeding the design-center maximum of 16,000 Volts, X-ray shielding may be necessary to protect users from harmful radiation. Adequate protection is maintained if the radiation level in contact with the viewing window remains below 6.25 mR/hr.

Technical Summary

The 17CEP4 is a 90-degree magnetic deflection, electrostatic-focus rectangular picture tube featuring a lightweight spherical faceplate and an aluminized P4 screen. It operates with a 6.3 V, 450 mA heater and does not require an ion trap magnet due to its short straight electron gun design. With a recommended anode operating voltage of 14,000 V and a maximum rating of 16,000 V, it provides a minimum useful screen area of 155 square inches. The tube's design-center ratings and electrostatic focus range (-50 to +350 V) make it a highly standardized component for mid-1950s television receivers.