16UP4 — Cathode Ray Picture Tube

A direct-view, rectangular glass cathode ray tube designed for television display applications, featuring magnetic focus and deflection, a grey filter faceplate, and an external single-field ion trap.

Overview

The 16UP4 is a specialized rectangular glass-construction cathode ray tube (CRT) designed primarily for direct-view television receiver applications. It incorporates an indirectly heated unipotential cathode, magnetic focusing, and magnetic deflection. To optimize picture contrast under ambient room lighting, the tube is equipped with a grey filter faceplate. The design produces a nominal raster size of 10 1/8 inches by 13 1/2 inches and requires an external single-field ion trap magnet to prevent ion burn on the phosphor screen.

Mechanical Design and Physical Dimensions

The 16UP4 features a rectangular glass bulb envelope with a nominal screen diagonal of 15 inches. The physical dimensions and tolerances of the bulb structure are tightly defined to ensure proper mounting and alignment within television cabinets:

The bulb's high-voltage anode connection is made via a recessed small cavity cap (designated J1-21). This contact is aligned with pin position #3 on the base within a tolerance of ± 10 degrees. The neck of the tube includes a designated clear space of approximately 3 5/8 inches from the reference line to the anode terminal, which must be kept clear to accommodate the external single-field ion trap magnet.

Electrical Connections and Basing

The 16UP4 utilizes a small shell duodecal 5-pin base (designated B5-57) with a 12D basing configuration. The electrical connections, viewed from the bottom of the base, are assigned as follows:

The heater is designed to operate on either AC or DC power, with a nominal rating of 6.3 V and a current draw of 0.6 A.

Ratings and Design Center Values

The operating limits of the 16UP4 are specified under the design center system. Operating the tube beyond these limits can impair performance or cause permanent damage.

Heater-Cathode Voltage Limits

Because the heater and cathode are electrically insulated but physically close, specific peak voltage limits must be maintained to prevent insulation breakdown:

• Heater negative with respect to cathode:
  • During the initial warm-up period (not to exceed 15 seconds): 410 V maximum.
  • After the equipment warm-up period: 125 V maximum.
• Heater positive with respect to cathode: 125 V maximum.

Typical Operating Conditions and Characteristics

Under typical operating conditions, the 16UP4 is configured with the following electrical parameters to achieve standard focus and brightness:

• DC Anode Voltage: 12,000 V
• DC Grid No. 2 Voltage: 300 V
• DC Grid No. 1 Voltage: −27 V to −63 V (This range represents the bias required for visual extinction of the undeflected focused spot.)
• DC Focusing Coil Current: Approximately 100 mA. This value is specified for a standard focus coil (such as No. 109 or equivalent), with the combined Grid No. 1 bias voltage and video signal voltage adjusted to produce a highlight brightness of 20 foot-lamberts on a 10 1/8-inch by 13 1/2-inch picture. The focus coil must be positioned such that the distance from the reference line to the center of the coil's air gap is exactly 3 inches.
• Ion Trap Magnet Strength: 23 Gausses (rated strength of the external single-field magnet).

Optical and Deflection Characteristics

The 16UP4 is designed for magnetic deflection and magnetic focusing, utilizing wide-angle scanning to minimize the overall length of the cabinet. The approximate deflection angles are:

• Horizontal Deflection Angle: 65 degrees
• Vertical Deflection Angle: 50 degrees
• Diagonal Deflection Angle: 70 degrees

The screen utilizes Phosphor No. 4, which exhibits the following optical properties:

• Fluorescent Color: White
• Phosphorescent Color: White
• Persistence: Medium
• Faceplate Light Transmission: Approximately 70% at the center of the faceplate, achieved via the integrated grey filter glass to enhance contrast under ambient light.

Technical Summary

The 16UP4 is a 15-inch rectangular glass cathode ray tube designed for direct-view television receivers. It features a 6.3 V, 0.6 A heater, a small shell duodecal 5-pin base, and a J1-21 recessed anode cap. Operating with a typical anode voltage of 12,000 V (up to a maximum of 15,000 V), it utilizes magnetic focusing and magnetic deflection with a diagonal deflection angle of 70 degrees. The tube incorporates a No. 4 white phosphor screen with medium persistence and a 70% transmission grey filter faceplate to deliver high-contrast images. Proper operation requires an external single-field ion trap magnet rated at 23 Gausses and a standard focusing coil positioned 3 inches from the reference line.