10AKP7 — High-Resolution Cathode Ray Tube
The 10AKP7 is a 10-inch round glass, magnetic-focus and magnetic-deflection cathode ray tube designed for applications requiring high resolution, a small spot size, excellent depth of focus, and a long-persistence display. It is primarily employed in radar indicators and oscillographs. The tube features a spherical faceplate made of gray glass and an aluminized screen utilizing the P7 phosphor.
Overview
The 10AKP7 is characterized by its high-resolution electron gun capabilities, which provide a smaller spot size and superior depth of focus. It is documented by manufacturers such as Raytheon and Sylvania. Sylvania notes that the tube can also be supplied with alternative screen phosphors under the broader 10AKP- designation.
Construction and Mechanical Specifications
The 10AKP7 is constructed with a round glass bulb designated as J84C (ASA designation) and features a gray glass faceplate with an approximate light transmission of 76% to 77% at the center. The screen is aluminized and utilizes a P7 phosphor, which provides a long-persistence characteristic. The fluorescence of this phosphor is blue-white, and its phosphorescence is yellow.
Physical Dimensions
The physical envelope of the tube is defined by the following dimensions:
- Overall Length: Sylvania specifies a nominal length of 17 13/16 ± 3/16 inches, while Raytheon lists 17 5/8 ± 3/8 inches.
- Bulb Diameter: 10 1/2 ± 1/16 inches maximum, with a minimum useful screen diameter of 9 inches.
- Neck Diameter: 1 7/16 ± 1/16 inches.
- Deflection Angle: Approximately 50 degrees.
The reference line of the tube is determined by the plane where a standard JEDEC No. 112 reference-line gauge seats against the bulb cone. The distance from this reference line to the seal line is 9 7/16 ± 3/16 inches. The distance from the reference line to the base is specified as 8 3/16 ± 3/16 inches by Raytheon and 8 3/8 inches nominal by Sylvania.
Base and Terminal Connections
The tube uses a Small-shell Duodecal 5-pin base (JEDEC No. B5-57) or a Small-shell Duodecal 7-pin base (JEDEC No. B7-51), with a 12D JEDEC basing designation. The high-voltage anode connection is made via a recessed small-cavity cap (JEDEC No. J1-21) located on the cone of the bulb. This anode contact is aligned with the vacant pin position No. 3 within ±10 degrees.
The terminal connections are assigned as follows:
The tube can be mounted in any position.
Heater and Electrical Ratings
The 10AKP7 operates with an indirectly heated cathode. The heater requirements and electrical limits are defined under two rating systems: Raytheon's Design Center Maximum Ratings and Sylvania's Absolute Maximum Ratings.
Heater Characteristics
- Heater Voltage: 6.3 Volts
- Heater Current: 0.6 ± 10% Ampere
- Cathode Connection: The cathode should be returned to the center tap or to one side of the heater transformer winding.
Direct Interelectrode Capacitances
The approximate direct interelectrode capacitances of the tube are:
- Cathode to all other electrodes: 5 µµf (pF)
- Grid No. 1 to all other electrodes: 8 µµf (pF)
Maximum Ratings Comparison
The maximum ratings differ depending on the rating system applied by the manufacturer:
Raytheon notes that its Design Center ratings incorporate a 10% safety factor. Under this system, if the maximum design-center values are not exceeded by more than 10%, the tube can sustain the combined effects of line voltage and component variation.
Typical Operating Conditions and Characteristics
For typical operation, both manufacturers specify an anode voltage of 8,000 Volts DC and a Grid No. 2 voltage of 700 Volts DC. Under these conditions, the operating parameters are:
- Anode Voltage: 8,000 Volts DC. In general, the anode voltage should not be less than 5,000 Volts, as decreasing anode voltage results in a reduction of both brightness and focus quality.
- Grid No. 2 Voltage: 700 Volts DC.
- Grid No. 1 Voltage Required for Cutoff: Raytheon lists this range as -20 to -80 Volts DC, while Sylvania lists it as -35 to -80 Volts DC (for visual extinction of an undeflected focused spot).
- Focusing Coil Current: Approximately 105 mA DC when using a JEDEC/RETMA No. 106 focusing coil positioned such that the distance from the yoke reference line to the center of the air gap is 3 1/4 inches.
- Line Width: 0.30 mm maximum, measured in accordance with MIL-E-1, paragraph 4.12.6.2, at an anode current of 200 µA.
- Spot Position (Undeflected): Raytheon specifies that the center of the unfocused, undeflected spot will fall within an 18 mm circle concentric with the tube face. Sylvania specifies that it will fall within a circle of 18 mm radius concentric with the tube face.
- Maximum Grid No. 1 Circuit Resistance: 1.5 Megohms.
Operational Precautions and Safety
Because the 10AKP7 operates at high voltages, Sylvania provides an explicit warning regarding X-ray radiation.
X-Ray Radiation Warning
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 Rated Anode Voltage or 16,000 volts, whichever is less.
Technical Summary
The 10AKP7 is a high-resolution, 10-inch round glass cathode ray tube featuring magnetic focus, magnetic deflection (50-degree deflection angle), and a long-persistence P7 aluminized screen. Operating with a standard 6.3 V, 0.6 A heater, it is optimized for radar indicators and oscillographs where high resolution, small spot size, and deep focus are critical. Typical operating conditions utilize an anode voltage of 8,000 V DC and a Grid No. 2 voltage of 700 V DC, with a Grid No. 1 cutoff voltage ranging from -20 V to -80 V DC (or -35 V to -80 V DC depending on the specification standard). The tube is housed in a J84C bulb with a small-shell Duodecal base and a J1-21 anode cap, and it can be operated in any mounting position.
