17BP4C Television Picture Tube
The 17BP4C is a direct-view cathode ray picture tube designed specifically for television receiver applications. It features a rectangular glass construction, a unipotential cathode, magnetic focus and deflection systems, and requires an external single-field ion trap. To optimize picture quality, the tube is built with a frosted grey filter faceplate and an external conductive coating.
Mechanical and Physical Specifications
The 17BP4C is constructed with a rectangular glass bulb envelope. Its physical dimensions and screen characteristics are highly standardized to fit specific television chassis designs:
- Overall Length: 19-1/4 +/- 3/8 inches
- Greatest Bulb Dimensions:
- Diagonal: 16-5/8 +/- 1/8 inches
- Width: 15-3/8 +/- 1/8 inches
- Height: 12-1/4 +/- 1/8 inches
- Minimum Useful Screen Dimensions:
- Diagonal: 15-3/8 inches
- Width: 14-1/4 inches
- Height: 10-3/4 inches
- Standard Raster Size: 14-1/4 inches by 10-3/4 inches
The electrical connection to the high-voltage anode is made via a recessed small cavity cap (J1-21), which is aligned with pin position #6 +/- 30 degrees. The tube's base is a small shell duodecal 5-pin configuration (B5-57) utilizing the Basing 12N arrangement.
Electro-Optical and Deflection Characteristics
The 17BP4C utilizes magnetic deflection and magnetic focusing. The approximate deflection angles for scanning the screen are:
- Horizontal Deflection: 65 degrees
- Vertical Deflection: 50 degrees
- Diagonal Deflection: 70 degrees
The screen is coated with Phosphor No. 4 (sulfide type), which exhibits white fluorescence and white phosphorescence with medium persistence. The frosted grey filter faceplate is designed to improve contrast, providing a light transmission of approximately 66% at the center of the screen.
Pin Connections and Interelectrode Capacitances
The small shell duodecal base (Basing 12N) provides the following pin connections:
The interelectrode capacitances of the tube are approximately:
- Cathode to all other electrodes: 5 uuf
- Grid No. 1 to all other electrodes: 6.5 uuf
- External conductive coating to anode: 750 uuf (minimum) to 1500 uuf (maximum)
The external conductive coating must be properly grounded to serve as a high-voltage filter capacitor in conjunction with the internal anode.
Electrical Ratings and Operating Conditions
The operating limits and typical characteristics of the 17BP4C are specified under the Design Center system.
Maximum Ratings
- Heater Voltage: 6.3 V
- Heater Current: 0.6 A
- Maximum DC Anode (Grid No. 3) Voltage: 16,000 V
- Maximum DC Grid No. 2 Voltage: 410 V
- Maximum Grid No. 1 Voltage:
- DC Negative-Bias Value: 125 V
- DC Positive-Bias Value: 0 V
- Positive-Peak Value: 2 V
- Maximum DC Peak Heater-Cathode Voltage:
- Heater negative with respect to cathode (during warm-up <= 15 seconds): 410 V
- Heater negative with respect to cathode (after warm-up): 150 V
- Heater positive with respect to cathode: 150 V
- Maximum Grid No. 1 Circuit Resistance: 1.5 Megohms
Typical Operating Conditions
For standard operation, the following typical values are used:
- DC Anode (Grid No. 3) Voltage: 12,000 V (Note: Operating the anode below 12,000 V is not recommended, as brilliance and definition decrease below this level.)
- DC Grid No. 2 Voltage: 300 V
- DC Grid No. 1 Voltage: -33 V to -77 V (required for visual extinction of the undeflected focused spot)
- DC Focusing Coil Current: Approximately 92 +/- 10% mA. This value applies when using a standard focus coil #109 or equivalent, with the distance from the reference line to the center of the air gap on the focus coil set to 3.0 inches. This is measured with the combined Grid No. 1 bias and video signal adjusted to produce a highlight brightness of 30 foot-lamberts on the 14-1/4 inches by 10-3/4 inches picture area.
- DC Ion Trap Current: Approximately 70 mA when using a standard coil #111.
Technical Summary
The 17BP4C is a rectangular glass television picture tube featuring a 70-degree diagonal deflection angle, magnetic focus, and magnetic deflection. It operates with a standard 6.3 V, 0.6 A heater and is rated for a maximum anode voltage of 16,000 V, with a typical operating anode voltage of 12,000 V to maintain optimal brilliance and definition. Utilizing a No. 4 sulfide-type phosphor, a frosted grey filter faceplate with 66% light transmission, and an external conductive coating, the 17BP4C provides a reliable, medium-persistence white display for direct-view television receivers.
