17ATP4 — Electrostatic-Focus Television Picture Tube

The 17ATP4 is a 17-inch, direct-view, rectangular glass cathode ray tube designed primarily for television receiver applications. It features low-voltage electrostatic focusing and magnetic deflection. The tube is closely related to several variants: the 17ATP4A is identical except for its metal-backed (aluminized) screen, while the 17AVP4 and 17AVP4A represent corresponding non-aluminized and aluminized models sharing similar electrical and physical profiles.

Construction and Optical Characteristics

The 17ATP4 is constructed with a rectangular glass envelope and a spherical faceplate. The faceplate is made of grey filter glass to improve picture contrast, providing a light transmission of approximately 66% to 71% at the center.

The screen utilizes a P-4 sulfide-type phosphor that produces a white fluorescence and phosphorescence with a short to short-to-medium persistence. While the base 17ATP4 and 17AVP4 models feature a non-metal-backed screen, the "A" suffix variants (17ATP4A and 17AVP4A) incorporate a metal-backed (aluminized) screen to enhance brightness and performance.

To prevent ion-burn damage to the screen, the tube requires an external, single-field ion trap magnet. Additionally, the outer surface of the bulb is treated with an external conductive coating that must be grounded during operation.

Mechanical Specifications and Basing

The tube has a nominal weight of approximately 13.5 lbs. Its physical dimensions and installation requirements are highly specific:

• Overall Length: 16 +1/4 -3/8 inches
• Greatest Bulb Dimensions: Diagonal of 16-5/8" ± 1/8", width of 15-3/8" ± 1/8", and height of 12-1/4" ± 1/8"
• Minimum Useful Screen Dimensions: Diagonal of 15-1/4", width of 14-1/4" to 14-5/16", height of 11-1/16" to 11-1/8", yielding a minimum useful screen area of approximately 149 square inches
• Raster Size: Approximately 10-3/8" x 13-7/8" to 10-3/4" x 14-1/4"
• Deflection Angles: Horizontal deflection of 80° to 85°, vertical deflection of 65°, and diagonal deflection of 90°

Electrical connections are made through a small shell duodecal 6-pin base (designation B6-63), conforming to the 12L basing diagram. The high-voltage anode connection is made via a recessed small cavity cap (J1-21) located on the bulb cone, which aligns with pin position #6 within a tolerance of ±30 degrees. Because of the physical tolerances of the glass envelope, the socket must not be rigidly mounted; it must have flexible leads to permit free movement.

Pin Connection Configuration

The bottom view of the 12L base provides the following pinout:

Electrical Ratings and Operating Conditions

The 17ATP4 operates with a unipotential cathode heated by a nominal 6.3-volt filament. The heater draws 0.6 Ampere (with a ±5% tolerance). Under standard JETEC test conditions (using a 25 V source and a 31.5-ohm series resistor), the heater warm-up time to reach 5.0 Volts is approximately 11 seconds.

Interelectrode Capacitances

• Cathode to all other electrodes: Approximately 5 µµf
• Grid No. 1 to all other electrodes: Approximately 6 µµf
• External conductive coating to anode: 750 µµf minimum to 1,500 µµf maximum (some specifications list a minimum of 1,200 µµf)

Operating Voltages and Limits

The tube's performance is highly dependent on maintaining adequate anode potential; brilliance and definition decrease significantly below 12,000 Volts. The operating limits are defined under both Design Center and Absolute Maximum rating systems:

Note on Grid No. 4: The negative limit on Grid No. 4 applies specifically when an AC voltage is provided for dynamic focusing. The typical operating range of -55 to +300 Volts (or -56 to +310 Volts) is specified at an anode current of 100 µA. Note on Grid No. 1 Cutoff: Visual extinction of an undeflected focused spot requires a bias of -33 to -77 Volts, while visual extinction of a focused raster requires -28 to -72 Volts. Extinction of a stationary focused spot requires approximately 5 Volts more negative bias than raster extinction.

Heater-Cathode Voltage Limits

• Heater negative with respect to cathode (during warm-up ≤ 15s): Max 410 V (Design Center) / 450 V (Absolute)
• Heater negative with respect to cathode (after warm-up): Max 180 V (Design Center) / 200 V (Absolute)
• Heater positive with respect to cathode: Max 180 V (Design Center) / 200 V (Absolute)

Circuit Parameters and Ion Trap

• Maximum Grid No. 1 Circuit Resistance: 1.5 Megohms
• Ion Trap Magnet: Requires a magnetic field strength of 31 Gausses minimum (for a typical PM magnet with a ±3 Gauss tolerance) or a nominal 37 Gausses. Alternatively, when using a JETEC No. 117 electromagnet with pole pieces centered over Grid No. 2 and rotated for maximum brightness, the average current is 28 mA DC.

Safety and X-Ray Shielding

When operating the 17ATP4, safety precautions regarding X-ray radiation must be observed. The tube is rated to permit operation at absolute anode voltages up to 17.6 Kilovolts. However, if the operating voltage exceeds 16,000 Volts or the manufacturer's maximum rated anode voltage (whichever is less), appropriate shielding may be necessary to protect personnel against potential X-ray exposure during prolonged close-range contact.