17BP4B — Direct-View Cathode Ray Picture Tube
The 17BP4B is a direct-view, rectangular glass cathode ray picture tube designed primarily for television receiver applications. It features a reflective metal-backed (aluminized) screen, magnetic focus, and magnetic deflection. The tube incorporates an electron gun designed for use with an external single-field ion-trap magnet, and its external conductive coating serves as a high-voltage filter capacitor when connected to ground.
Construction and Physical Characteristics
The 17BP4B is constructed with a rectangular glass envelope and a neutral-density grey filter faceplate that provides approximately 66% light transmission at the center, improving picture contrast under ambient light. The screen utilizes Phosphor No. 4 (Sulfide Type), which exhibits white fluorescence and white phosphorescence with medium persistence.
Mechanical Dimensions
The physical dimensions of the tube are as follows:
- Overall Length: 19 1/4 ± 3/8 inches
- Greatest Bulb Diagonal: 16 5/8 ± 1/8 inches
- Greatest Bulb Width: 15 3/8 ± 1/8 inches
- Greatest Bulb Height: 12 1/4 ± 1/8 inches
- Minimum Useful Screen Diagonal: 15 3/8 to 15 1/2 inches
- Minimum Useful Screen Width: 14 1/4 inches
- Minimum Useful Screen Height: 10 3/4 to 11 1/16 inches
- Standard Raster Size (3x4 Aspect Ratio): 14 1/4 inches x 10 3/4 inches
Deflection and Focus
The tube utilizes magnetic deflection and magnetic focus. The approximate deflection angles are:
- Horizontal: 65°
- Vertical: 50°
- Diagonal: 70°
An external single-field ion-trap magnet is required to prevent ion burn on the phosphor screen.
Electrical Specifications and Pin Connections
The 17BP4B uses a small-shell duodecal 5-pin base (designation B5-57) and is compatible with both 12N and 12D basing configurations. High voltage is applied via a recessed small cavity cap (designation J1-21) located on the bulb side. The anode contact aligns with vacant pin position No. 6 within a tolerance of ±30 degrees.
Pinout Configuration (Basing 12N / 12D)
- Pin 1: Heater
- Pin 2: Grid No. 1
- Pin 10: Grid No. 2
- Pin 11: Cathode
- Pin 12: Heater
- Anode Cap: Grid No. 3 / Anode (connected internally)
Heater Ratings
- Heater Voltage: 6.3 Volts
- Heater Current: 0.6 Ampere (with a tolerance of ±10%)
Interelectrode Capacitances
- Cathode to all other electrodes: Approximately 5 µµF
- Grid No. 1 to all other electrodes: 6 to 6.5 µµF
- External conductive coating to anode: Minimum 750 µµF, maximum 1500 to 2000 µµF
Maximum Ratings (Design Center Values)
The following maximum ratings must be observed to ensure reliable operation and prevent damage to the tube:
Operating Conditions and Characteristics
The 17BP4B can be operated under standard comparative conditions or optimized recommended conditions. Brilliance and definition decrease if the anode voltage is reduced; therefore, the anode voltage should not be operated below 12,000 Volts.
JETEC Comparative Operating Conditions
- DC Anode (Grid No. 3) Voltage: 12,000 Volts
- DC Grid No. 2 Voltage: 300 Volts
- DC Grid No. 1 Voltage (for visual extinction of undeflected focused spot): -33 to -77 Volts
- DC Focusing Coil Current: 92 mA (with a tolerance of ±10% to ±20% depending on the specific focus coil setup, assuming a standard focus coil No. 109 or equivalent, with the air gap center positioned 3.0 inches from the reference line, and the combined Grid No. 1 bias and video signal adjusted for 30 to 35 foot-lamberts highlight brightness)
- DC Ion-Trap Current: 70 to 75 mA (using standard single-field ion-trap magnet coil No. 111 or equivalent, positioned 5 1/2 inches from the yoke reference line; or 75 ± 50% mA)
Recommended Operating Conditions
- DC Anode (Grid No. 3) Voltage (at average brightness of 20 foot-lamberts): 14,000 Volts
- DC Grid No. 2 Voltage: 300 Volts
- DC Grid No. 1 Voltage (for visual extinction of undeflected focused spot): -33 to -77 Volts
- DC Focusing Coil Current: Approximately 115 mA (using standard coil No. 109 positioned at 3 3/4 inches)
- Ion-Trap Field Intensity: Approximately 35 gausses (using a single-field magnet adjusted to optimum)
Performance and Drive Characteristics
Under typical operating conditions with a heater voltage of 6.3V, Grid No. 2 voltage of 250V, anode voltage of 14,000V, and a focused 525-line raster (10 3/4" x 14 1/4"):
- Highlight Brightness: Rises from approximately 0 foot-lamberts at 10V drive to approximately 62 foot-lamberts at 28V drive.
- Anode Current: Rises from approximately 0 µA at 10V drive to approximately 820 µA at 45V drive.
Related Designations
The 17BP4B belongs to a family of closely related cathode ray tubes, which includes the 17BP4, 17BP4A, and 17BP4C. The primary distinguishing feature of the 17BP4B is its aluminized (reflective metal-backed) screen, which enhances light output and picture brightness compared to non-aluminized variants. It shares the external conductive coating feature with the 17BP4A and 17BP4C models.
