19CAP4 — Rectangular Glass Picture Tube

The 19CAP4 is a direct-view rectangular glass picture tube designed for television receivers. It features a short straight electron gun that eliminates the need for an ion trap, a short neck, and a wide 110-degree diagonal deflection angle. The tube is constructed with a grey-tinted, flat compound faceplate, a tri-potential focus system, and a metal-backed (aluminized) screen.

Mechanical Design and Physical Characteristics

The 19CAP4 is built with a rectangular glass envelope and has the following approximate deflection angles:

• Diagonal: 110°
• Horizontal: 99°
• Vertical: 82°

The screen utilizes a P4 aluminized phosphor, which provides white fluorescence with medium persistence. The faceplate is made of grey filter glass with approximately 78% light transmission. The minimum useful screen dimensions are 15 1/8 by 12 inches, yielding a minimum useful screen area of 172 square inches.

The physical structure of the tube weighs approximately 13 1/2 lbs. It features a recessed small cavity cap (J1-21) bulb contact and a small wafer Eightar 7-pin base (B7-208) with an 8JR basing configuration. The anode contact is aligned such that the J1-21 contact aligns with Pin Position No. 4 within a tolerance of ±30°. During manufacturing, a bulge at the splice-line seal may increase the maximum envelope width, diagonal, and height by up to 1/4 inch, but this bulge will not protrude more than 1/8 inch beyond these dimensions at any point.

Electrical Connections and Pinout

The 19CAP4 is equipped with an indirectly heated cathode. The heater requires a nominal voltage of 6.3 Volts and a current of 0.6 Ampere ± 5%.

Pin Configuration (Basing 8JR)

The bottom view of the 8JR base provides the following pin connections:

Within the tube, Grid No. 5 and the collector are connected together and referred to as the anode, which terminates at the recessed small cavity cap.

Interelectrode Capacitances

The approximate capacitances of the tube's electrodes are:

• Cathode to all other electrodes: 5 uuf
• Grid No. 1 to all other electrodes: 6 uuf
• External conductive coating to anode capacitance: 1000 uuf (minimum) to 1500 uuf (maximum)

Operating Conditions and Circuit Design

The electrical ratings of the 19CAP4 are established under the Design-Maximum Rating System. Designers must adhere to these limits to ensure reliable operation.

Absolute Maximum Ratings

• Anode Voltage: 20,000 Volts dc
• Grid No. 4 Voltage (Focusing Electrode): -350 to +700 Volts dc
• Grid No. 2 Voltage: 600 Volts dc
• Grid No. 1 Voltage:
  • Negative bias value: 154 Volts dc
  • Positive bias value: 0 Volts dc
  • Positive peak value: 2 Volts
• Peak Heater-Cathode Voltage:
  • Heater negative with respect to cathode during warm-up (not to exceed 15 seconds): 450 Volts dc
  • Heater negative with respect to cathode after warm-up: 200 Volts dc
  • Heater positive with respect to cathode: 200 Volts dc

Recommended Operating Conditions

For typical operation, the following parameters are recommended:

• Anode Voltage: 16,000 Volts dc
• Grid No. 4 Voltage: 0 to +400 Volts dc (for focus with an anode current of 100 uA and a 15 1/8 x 12 inch raster; this electrode is listed as Grid No. 3 in some text)
• Grid No. 2 Voltage: 500 Volts dc
• Grid No. 1 Voltage: -43 to -78 Volts dc (for visual extinction of the focused raster; achieving extinction of a stationary focused spot requires approximately 5 Volts more negative values)

Circuit and Installation Requirements

• Grid No. 1 Circuit Resistance: Must not exceed a maximum value of 1.5 Megohms.
• Cathode Return: The cathode should be returned to one side or to the mid-tap of the heater transformer winding.
• Grounding: The external conductive coating (C) must be grounded.
• Anti-Corona Protection: An anti-corona coating is applied around the anode connector to prevent electrical discharge.

Technical Summary

The 19CAP4 is a 110° rectangular glass television picture tube featuring a short neck, a short straight electron gun, and a tri-potential focus system. Operating with a 6.3 V, 0.6 A heater, it delivers a 172 sq. in. viewing area on an aluminized P4 white phosphor screen. With a maximum anode voltage rating of 20,000 V dc and recommended operation at 16,000 V dc, the tube provides a reliable display solution when installed with proper grounding of its external conductive coating and appropriate cathode return configurations.