19BUP4 — Rectangular Glass Cathode Ray Tube

The 19BUP4 is a 19-inch direct-view rectangular glass cathode ray tube designed for television applications. It features a wide-angle diagonal deflection of 114 degrees, electrostatic focusing, and magnetic deflection. The tube is constructed with a straight electron gun that requires no ion trap, an aluminized P4 screen, and a low-power heater designed for rapid warm-up.

Design and Mechanical Construction

The 19BUP4 utilizes a J149A1 glass bulb envelope with a relatively flat compound-radius faceplate. To achieve its wide 114-degree deflection angle while remaining compatible with standard 110-degree components, the envelope features special internal contouring in the deflection yoke region. The neck of the tube is terminated in a hard lead stem, and it uses a short B7-208 base with an indexing lug. The electrical connections are arranged according to the 8HR basing configuration.

The anode contact is a recessed small cavity cap (J1-21 design), which is aligned with Pin #4 within a tolerance of ±30 degrees. The area surrounding the anode button is covered with an insulating coating to prevent electrical discharge.

Physical Dimensions

The physical specifications of the tube are as follows:

• Overall Length: 11-5/8 ± 3/16 inches
• Neck Length: 4-3/8 ± 1/8 inches
• Greatest Bulb Dimensions:
  • Diagonal: 18-5/8 ± 1/8 inches
  • Width: 16-13/32 ± 1/8 inches
  • Height: 13-11/32 ± 1/8 inches
• Minimum Useful Screen Dimensions:
  • Diagonal: 17-9/16 inches
  • Width: 15-1/8 inches
  • Height: 12 inches
  • Total Area: 172 square inches

For proper installation, the reference line of the tube is determined using a JEDEC #126 gauge. Additionally, the socket must not be rigidly mounted; it must have flexible leads and free movement to accommodate the tube.

Heater and Electrical Characteristics

The 19BUP4 is designed with a highly efficient, low-power heater that operates at less than 1/4 watt. This low power requirement enables rapid warm-up, allowing the screen to reach an acceptable level of brightness quickly.

Note: The heater power is calculated as 2.2 V multiplied by 0.102 A.

Direct Interelectrode Capacitances

The approximate capacitances of the tube electrodes are:

• Cathode to All Other Electrodes: 1.2 µµF
• Grid #1 to All Other Electrodes: 5.5 µµF
• External Coating Capacitance: 1300 µµF (minimum) to 1700 µµF (maximum)

Deflection Angles

The design of the envelope and yoke region supports the following approximate deflection angles:

• Diagonal: 114 degrees
• Horizontal: 102 degrees
• Vertical: 85 degrees

Optical Characteristics

The tube is equipped with an aluminized P4 phosphor screen, which produces a white fluorescence with medium-short persistence. The faceplate exhibits a light transmission of approximately 78% at the center.

Cathode Drive Service Ratings and Operating Conditions

All voltage values for cathode drive service are specified as positive with respect to Grid #1, unless otherwise noted.

Absolute Maximum Ratings

Operating the tube beyond these absolute maximum limits may cause permanent damage:

• Anode Voltage: 18,750 V DC maximum (Note: The Anode, Grid #3, and Grid #5 are internally connected)
• Grid #4 Voltage (Focusing Electrode): -200 V to +500 V DC
• Grid #2 Voltage: 250 V DC maximum
• Cathode Voltage:
  • Positive-Bias DC Value: 154 V maximum
  • Positive-Peak Value: 220 V maximum
  • Negative-Bias DC Value: 0 V maximum
  • Negative-Peak Value: 2 V maximum
• Peak Heater-Cathode Voltage:
  • Heater Negative to Cathode (during warm-up ≤ 15 seconds): 450 V maximum
  • Heater Negative to Cathode (after warm-up): 200 V maximum
  • Heater Positive to Cathode: 200 V maximum

Typical Operating Conditions

Under typical operating conditions, the tube is configured as follows:

• Anode Voltage: 14,000 V DC
• Grid #4 Voltage (Focus): 0 to 400 V DC
• Grid #2 Voltage: 100 V DC
• Grid #1 Voltage: 0 V DC
• Cathode Voltage (for visual extinction of focused raster): +45 V to +60 V DC

Note: For the cutoff of an undeflected focus spot, the absolute bias value increases by approximately 3 V.

Maximum Circuit Values

• Grid #1 Circuit Resistance: 1.5 Megohms maximum

Safety and Handling

Because the 19BUP4 operates at high voltages, safety precautions must be observed:

• X-ray Radiation: If the tube is operated at anode voltages exceeding 16,000 V, X-ray shielding may be necessary to protect personnel from injury during prolonged, close-range exposure.
• Mechanical Stress: To prevent damage to the glass neck and base, the socket must have flexible leads and be free to move rather than being rigidly mounted.