10QP7 — Magnetic Focus and Deflection Cathode Ray Tube
The 10QP7 is a specialized magnetic focus and magnetic deflection cathode ray tube (CRT) designed for applications requiring a high-intensity, finely focused spot. It features a 10.5-inch nominal diameter faceplate and is equipped with a long-persistence cascade fluorescent screen.
Overview
The 10QP7 is designed for precision display applications where image retention and high spot resolution are critical. The tube utilizes magnetic fields for both focusing the electron beam and deflecting it across the screen. A key performance feature of the 10QP7 is its ability to produce a small, high-intensity spot, making it suitable for detailed radar, medical, or industrial imaging systems. The tube operates with a relatively narrow deflection angle of 50 degrees, which helps minimize deflection distortion and maintain spot uniformity across the useful screen area.
Screen and Phosphor Characteristics
The tube is constructed with a #7 (P7) phosphor screen, which is a cascade-type screen designed for long persistence. This phosphor configuration exhibits the following characteristics:
- Fluorescence: Blue (initial excitation color)
- Phosphorescence: Yellow (afterglow color)
- Persistence: Long
The cascade structure of the P7 phosphor allows the initial high-energy electron impact to excite a short-persistence blue light, which in turn excites a secondary phosphor layer that emits a long-persistence yellow glow. This behavior is highly advantageous for displaying slow-scan or non-repetitive sweep information.
Mechanical Specifications and Physical Dimensions
The 10QP7 is housed in a glass envelope with specific physical dimensions and external treatments to ensure proper electrical insulation and mechanical fit:
- Maximum Bulb Diameter: 10 1/2 ± 1/16 inches
- Minimum Useful Screen Diameter: 9 inches
- Overall Length: 17 5/8 ± 3/8 inches
- Neck Diameter: 1 7/16 ± 1/16 inches
- Faceplate Curvature Radius: 42 inches
- Inner Cone Radius: 20 inches
- Face Corner Radius: 7/16 inch
- Deflection Angle: 50°
- Mounting Position: Any
Reference Line Determination
The reference line, which serves as the datum point for positioning external deflection and focusing components, is determined by the position where a ring gauge with an internal diameter of 1.5000 inches (+0.003", -0.000") and a length of 2 inches rests on the bulb cone.
External Coatings and Handling
The envelope incorporates specialized external coatings to manage electrical fields and prevent corona discharge:
- Dri-Film Coating: Dri-Film #9987 is applied to the bulb cone in the region between the faceplate and the reference line.
- Conductive Coating: A conductive coating is applied to the neck, extending 5 inches from the reference line toward the base.
- Handling Caution: Due to the delicate nature of the anti-corona treatment, the tube must not be handled by the portion of the bulb coated with the anti-corona material.
Base, Cap, and Terminal Connections
The 10QP7 utilizes a duodecal base configuration for low-voltage connections and a separate high-voltage cap for the collector.
- Base Type: Designated as a Small Shell Duodecal 6-Pin base in electrical specifications, and also identified as a Small Shell Duodecal 5-Pin Base (B5-57) in mechanical drawings.
- Anode/Collector Cap: A Recessed Small Cavity Cap (J1-21) is located on the side of the bulb cone to provide a secure, high-voltage connection.
Pinout Configuration
When viewed from the bottom of the base, the terminal connections are assigned as follows:
Electrical Characteristics and Ratings
The electrical parameters of the 10QP7 are divided into heater characteristics, interelectrode capacitances, and design-center maximum ratings.
Heater Characteristics
The tube's electron gun uses an indirectly heated cathode with the following heater specifications:
- Heater Voltage: 6.3 V
- Heater Current: 0.6 ± 10% A
- Maximum Peak Heater-Cathode Voltage:
- Heater negative with respect to cathode: 175 V DC
- Heater positive with respect to cathode: 175 V DC
Direct Interelectrode Capacitances
The approximate capacitances between the internal electrodes, measured without external shielding, are:
- Grid #1 to all other electrodes: 4.0 pF
- Cathode to all other electrodes: 3.5 pF
Design Center Maximum Ratings
These ratings represent the limiting values above which the serviceability and safety of the tube may be impaired:
- Collector Voltage (including Grid #2): 20,000 V DC
- Grid #1 Voltage:
- Negative-Bias Value: 350 V DC
- Positive-Bias Value: 0 V DC
- Positive-Peak Value: 2 V DC
- Maximum Grid #1 Circuit Resistance: 1.5 MΩ
Typical Operation and Focusing Setup
Under typical operating conditions, the 10QP7 is configured with a high collector voltage to maximize spot brightness and resolution.
- Collector Voltage (including Grid #2): 20,000 V DC
- Grid #1 Voltage (for visual extinction of deflected focus spot): -63 to -147 V DC
- Undeflected Spot Position: 0.590 inch maximum deviation from the physical center.
Focusing and Deflection Operation
To achieve the specified high-intensity small spot, the tube requires precise alignment of the external focusing coil:
- Focus Coil Specification: Designed for use with a standard focus coil #106 or an equivalent magnetic focusing assembly.
- Focus Coil Current: Approximately 190 mA DC.
- Focus Coil Position: The focus coil must be positioned such that the distance from its air gap to the bulb's reference line is exactly 3.25 inches.
- Calibration Condition: During setup, the Grid #1 bias voltage and the video signal voltage are adjusted to maintain an anode current of 100 microamperes.
Technical Summary
The 10QP7 is a 10.5-inch magnetic focus and magnetic deflection cathode ray tube featuring a long-persistence #7 cascade phosphor screen (emitting blue fluorescence and yellow phosphorescence). It operates with a 6.3 V, 0.6 A heater and is rated for a maximum collector voltage of 20,000 V DC. The tube is designed to produce a highly concentrated, high-intensity spot when paired with a standard focus coil #106 operating at approximately 190 mA DC. Its physical construction includes a Small Shell Duodecal base, a recessed small cavity anode cap, and specialized Dri-Film and conductive bulb coatings to ensure stable high-voltage operation.
