17LP4 — Direct-View Cathode Ray Picture Tube

The 17LP4 is a 17-inch, direct-view, rectangular glass cathode ray picture tube designed primarily for television receiver applications. It features magnetic deflection, low-voltage electrostatic focusing, a cylindrical grey filter faceplate, and an external conductive envelope coating.

A closely related variant, the 17LP4A, is identical to the 17LP4 in all physical and electrical characteristics except that it incorporates an aluminized screen to enhance picture brightness, whereas the standard 17LP4 utilizes a non-aluminized screen.

Physical and Optical Characteristics

The 17LP4 is constructed with a rectangular glass bulb and a cylindrical grey filter faceplate. The faceplate is designed to improve picture contrast under ambient room lighting. Depending on the specification, the light transmission of this faceplate is rated at approximately 72%, or approximately 66% at the center.

Screen and Phosphor Specifications

The tube utilizes a sulfide-type Phosphor No. 4 (P4), which produces a white fluorescence and a white phosphorescence with medium persistence. The minimum useful screen dimensions and physical boundaries are:

• Minimum Useful Screen Diagonal: 15 5/16 inches
• Minimum Useful Screen Width: 14 1/4 inches
• Minimum Useful Screen Height: 10 3/4 inches (with a typical raster size of 14 1/4 inches x 10 3/8 inches)

Physical Dimensions

The envelope dimensions of the tube are as follows:

Deflection and External Components

The tube is designed for magnetic deflection with the following approximate deflection angles:

• Horizontal Deflection Angle: 65 degrees
• Diagonal Deflection Angle: 70 degrees

To prevent ion burn on the screen, the tube requires an external, single-field ion trap magnet (such as a RETMA #111 or equivalent) positioned on the neck. Additionally, the outer surface of the funnel is coated with an external conductive layer. This coating must be grounded and forms a high-voltage filter capacitor in conjunction with the internal conductive coating (collector).

Electrical Connections and Pinout

The 17LP4 uses a Small Shell Duodecal 6-Pin base (B6-63) with a 12L basing configuration. High-voltage connection to the anode (comprising Grid No. 3, Grid No. 5, and the collector) is made via a Recessed Small Cavity Cap (J1-21) located on the side of the bulb. The cavity cap is aligned with pin position No. 6 within a tolerance of ±30 degrees.

Heater Ratings

The heater is designed for AC or DC operation:

• Heater Voltage: 6.3 Volts
• Heater Current: Approximately 0.6 Ampere

Pin Assignment (Bottom View)

The electrical connections for the 12L basing arrangement are detailed below:

Interelectrode Capacitances

The direct interelectrode capacitances of the tube are approximately:

• Cathode to all other electrodes: 5 μμF (pF)
• Grid No. 1 to all other electrodes: 6 μμF (pF)
• External conductive coating to collector/anode: 750 μμF (minimum) to 1500 μμF (maximum)

Absolute and Design-Maximum Ratings

The following limits are established under the Design Center system and represent the maximum safe operating boundaries for the 17LP4:

Heater-Cathode Voltage Limits

To prevent insulation breakdown between the heater and cathode, the peak heater-cathode voltage must not exceed the following limits:

• Heater negative with respect to cathode during warm-up (≤ 15 seconds): 410 Volts DC
• Heater negative with respect to cathode after warm-up: 180 Volts DC
• Heater positive with respect to cathode: 180 Volts DC

Typical Operating Conditions and Characteristics

The 17LP4 can be operated under different anode voltage configurations. While typical characteristics are often specified at an anode potential of 12,000 V, a recommended operating point of 14,000 V is also documented. Operating the tube below 14,000 V may result in a decrease in picture brilliance and definition.

Operating Points Comparison

Focusing Voltage Calculations

The electrostatic focusing electrode (Grid No. 4) operates at a low voltage relative to the high-voltage collector. The focus range is designed to cover -0.4% to +2.2% of the collector voltage.

• Calculation at 12,000 V:
  • Minimum focus voltage: 12,000 V * (-0.004) = -48 V
  • Maximum focus voltage: 12,000 V * 0.022 = +264 V (specified as approximately +260 V)
• Calculation at 14,000 V:
  • Minimum focus voltage: 14,000 V * (-0.004) = -56 V
  • Maximum focus voltage: 14,000 V * 0.022 = +308 V (specified as approximately +310 V)

These calculations demonstrate how the focusing voltage scales proportionally with the overall anode potential to maintain a sharp, undeflected spot.

Safety Considerations

When operating the 17LP4, appropriate safety precautions must be observed regarding high voltages and potential radiation. If the tube is operated at or near its maximum rated anode voltage of 16,000 V, X-ray radiation shielding may be necessary to protect equipment operators and users. Adequate shielding should always be implemented if the operating anode voltage exceeds 16,000 V or the maximum rated voltage, whichever is less.

Technical Summary

The 17LP4 is a 17-inch rectangular glass television picture tube utilizing magnetic deflection (65° horizontal, 70° diagonal) and low-voltage electrostatic focusing. It is equipped with a 6.3 V, 0.6 A heater, a Small Shell Duodecal 6-Pin base (B6-63), and a recessed small cavity cap (J1-21) for the high-voltage anode.

The tube features a P4 white-emitting phosphor screen with medium persistence, which is non-aluminized in the standard 17LP4 and aluminized in the 17LP4A variant. With a maximum anode rating of 16,000 V, the tube is typically operated at 12,000 V to 14,000 V, requiring an external single-field ion trap magnet of approximately 35 Gausses and a grounded external conductive coating to complete its high-voltage filtering system.