16AMP7 — Electrostatic Deflection and Focus Oscilloscope Tube

Overview

The 16AMP7 is a 16-inch direct-viewed, round glass cathode-ray tube designed for oscilloscope applications. It features electrostatic deflection, electrostatic focus, post-deflection acceleration, and an aluminized screen. The tube is equipped with a P7 phosphor screen as standard, which provides blue-white fluorescence, yellow phosphorescence, and long persistence. However, it can also be supplied with other screen phosphors. The faceplate is constructed of gray filter glass with an approximate light transmittance of 76 percent.

Mechanical Design and Physical Dimensions

The 16AMP7 is a large-scale cathode-ray tube with a nominal bulb diameter of 16 inches (with a tolerance of ±1/8 inch) and a minimum useful screen diameter of 15 inches. The overall length of the tube is 22 3/4 inches (±3/8 inch). The tube weighs approximately 20 pounds.

Base and Contacts

The tube utilizes a Medium Shell Diheptal 12-Pin base (designation B12-37) with a 14Q basing arrangement. It features specific external contacts for high-voltage and deflection connections:

• Bulb Contact: A recessed small cavity cap (designation J1-21) is used for the Anode No. 3 (post-accelerator) connection.
• Neck Contacts: Small ball contacts (designation J1-25) are provided for the Anode No. 2 and deflection plate connections.

Alignment and Deflection Geometry

The physical alignment of the contacts and traces is tightly controlled:

• The J1-21 bulb contact aligns with the D3-D4 trace within ±10 degrees and aligns with Pin No. 11.
• The J1-25 neck contact (Anode No. 2) aligns with the D1-D2 trace within ±2 1/2 degrees.
• The D3-D4 trace aligns with Pin No. 11 within ±10 degrees.
• A positive voltage applied to deflecting plate D1 deflects the electron beam approximately toward Pin No. 8.
• A positive voltage applied to deflecting plate D3 deflects the beam approximately toward Pin No. 4.
• The angle between the D1-D2 and D3-D4 traces is 90 ± 1 degrees.

Electrical Characteristics and Interelectrode Capacitances

The 16AMP7 operates with a nominal heater voltage of 6.3 Volts and a heater current of 0.6 Amperes (with a tolerance of ±10%).

Direct Interelectrode Capacitances

The direct interelectrode capacitances of the tube are approximately as follows:

• Cathode to all other electrodes: 7 µµF
• Grid No. 1 to all other electrodes: 8 µµF
• Between deflecting plates 1-2: 4 µµF
• Between deflecting plates 3-4: 3 µµF
• Deflecting plate 1 to all other electrodes: 12.5 µµF
• Deflecting plate 2 to all other electrodes: 12.5 µµF
• Deflecting plate 3 to all other electrodes: 8.5 µµF
• Deflecting plate 4 to all other electrodes: 8.5 µµF

Absolute Maximum Ratings

The absolute maximum ratings define the operating limits beyond which the safety and performance of the 16AMP7 may be severely compromised:

Note: Anode input is defined as the product of the Anode No. 2 voltage and the average Anode No. 2 current.

Typical Operating Conditions

Under typical operating conditions, the 16AMP7 is configured with the following parameters:

• Anode No. 3 (Post Accelerator) Voltage: 12,000 Volts dc
• Anode No. 2 Voltage: 7,500 Volts dc
• Anode No. 1 Voltage for Focus: 1,760 to 2,670 Volts dc
• Grid No. 1 Voltage Required for Cutoff: -160 to -240 Volts dc (for visual extinction of an undeflected focused spot)
• Deflection Factors:
  • Deflecting Plates 1-2: 96 to 150 Volts dc/Inch
  • Deflecting Plates 3-4: 96 to 150 Volts dc/Inch
• Modulation: 37 Volts Max. (measured in accordance with MIL-E-1 specification at a post-accelerator current of 25 µA)
• Line Width 'A': 0.5 mm (measured at a post-accelerator current of 25 µA)
• Focus Electrode Current: -25 to +25 µA dc (measured at a post-accelerator current of 25 µA)
• Spot Position (Undeflected): Within a 20 mm square

Deflecting plates 1 and 2 are physically positioned nearer to the screen than plates 3 and 4.

Circuit Values

To ensure stable operation, the external circuit design must adhere to the following maximum resistance limits:

• Grid No. 1 Circuit Resistance: 1.5 Megohms maximum
• Resistance in Any Deflection Plate Circuit: 5.0 Megohms maximum

Safety and X-Ray Warning

When operating the 16AMP7, precautions must be taken regarding X-ray radiation. X-ray radiation shielding may be necessary to protect against possible danger of personal injury from prolonged exposure at close range if the tube is operated at voltages higher than the manufacturer's maximum anode voltage or 16,000 volts, whichever is less.

Technical Summary

The 16AMP7 is a specialized 16-inch round glass cathode-ray tube designed for high-performance oscilloscope applications. It integrates electrostatic focus and deflection with post-deflection acceleration to achieve precise beam control and high brightness on its aluminized screen. Standardized with a long-persistence P7 phosphor, it is well-suited for displaying slow-moving or transient waveforms. The electrical design is characterized by a 6.3 V, 0.6 A heater, moderate interelectrode capacitances, and strict operating limits, including a maximum post-accelerator voltage of 17,600 V and a maximum anode input of 6 W. Proper implementation requires adhering to specified grid and deflection circuit resistance limits and implementing adequate X-ray shielding when operating near high-voltage thresholds.