19BHP4 Cathode Ray Tube
The 19BHP4 is a 19-inch rectangular glass picture tube designed for television display applications. It features electrostatic focusing and magnetic deflection, utilizing an aluminized fluorescent screen with a P4 phosphor and a spherical gray faceplate. The tube incorporates a non-ion trap gun and an external conductive coating that serves as a filter capacitor when properly grounded.
Mechanical Specifications and Construction
The 19BHP4 is constructed with a J149-A1 glass bulb and has a rectangular screen profile. The faceplate is a spherical gray glass with approximately 76% light transmittance at the center. The screen is aluminized to enhance brightness and efficiency.
Physical Dimensions
The physical envelope of the tube has the following dimensional specifications:
- Overall Length: 11 3/4 ± 5/16 inches
- Neck Length: 4 1/2 ± 3/16 inches
- Greatest Diagonal Dimension: 18 5/8 ± 1/8 inches
- Greatest Width: 16 13/32 ± 1/8 inches
- Greatest Height: 13 11/32 ± 1/8 inches
Screen Dimensions (Projected Minimum Useful)
- Diagonal: 17 9/16 inches
- Horizontal Axis: 15 1/8 inches
- Vertical Axis: 12 inches
- Total Area: 172 square inches
Deflection Angles (Approximate)
- Diagonal: 114 degrees
- Horizontal: 102 degrees
- Vertical: 87 degrees
Bulb and Base Connections
The tube uses a JETEC No. J1-21 (or J1-J2) bulb contact for the high-voltage anode connection, which is aligned with Pin No. 4 within a tolerance of ± 30 degrees. The base is a JETEC No. B7-237 or B7-208, utilizing the 8HR basing configuration.
Heater and Basing Configuration
The 19BHP4 is equipped with an indirectly heated cathode. The heater is designed for a nominal voltage of 6.3 V and a current of 600 mA.
Heater Characteristics
- Nominal Heater Voltage: 6.3 V
- Nominal Heater Current: 600 ± 10% mA
- Heater Warm-Up Time: 11 seconds
- Calculated Heater Power: 6.3 V × 0.6 A = 3.78 W
Basing Diagram (8HR)
The 8HR base configuration provides the following pin connections, viewed from the bottom of the tube:
Electrical Characteristics and Capacitances
The direct interelectrode capacitances of the 19BHP4 are approximately:
- Cathode to all other electrodes: 5 pF
- Grid No. 1 to all other electrodes: 6 pF
- External conductive coating to anode: 1000 pF minimum, 1500 pF maximum
The external conductive coating, when connected to a system ground, forms a filter capacitor with the internal anode coating to assist in high-voltage ripple filtering.
Operating Conditions and Ratings
The ratings of the 19BHP4 are established under the Design Maximum System. All voltages are positive and measured with respect to the cathode unless otherwise specified.
Design Maximum Ratings
- Anode Voltage: 15,000 minimum to 22,000 maximum volts
- Grid No. 4 (Focusing Electrode) Voltage: -500 to +1000 volts
- Grid No. 2 Voltage: 400 minimum to 700 maximum volts
- Grid No. 1 Voltage:
- Maximum Negative DC Value: 140 volts
- Maximum Negative Peak Value: 200 volts
- Maximum Positive DC Value: 0 volts
- Maximum Positive Peak Value: 2 volts
- Heater Voltage: 5.7 minimum to 6.9 maximum volts
- Maximum Heater-Cathode Voltage:
- Heater negative with respect to cathode (during warm-up ≤ 15 seconds): 410 volts
- Heater negative with respect to cathode (after warm-up): 180 volts
- Heater positive with respect to cathode: 180 volts
Typical Operating Conditions
Under typical operating conditions, the tube is set to the following parameters:
- Anode Voltage: 18,500 volts DC
- Grid No. 4 Voltage: 250 volts DC (individual tubes focus within a range of 0 to 500 volts)
- Grid No. 2 Voltage: 450 volts DC
- Grid No. 1 Voltage (for visual extinction of focused raster): -28 to -61 volts DC
Circuit Design and Maximum Values
To ensure reliable operation and protect the tube from internal arc damage, specific circuit resistance limits must be observed:
- Maximum Grid No. 1 Circuit Resistance: 1.5 megohms
- Minimum Grid No. 2 Circuit Resistance: 0.1 megohms
- Minimum Focusing Electrode (Grid No. 4) Circuit Resistance: 0.1 megohms
The inclusion of protective resistance in the Grid No. 2 and focusing electrode circuits is highly advisable to prevent damage from transient discharges.
Technical Summary
The 19BHP4 is a 19-inch rectangular glass cathode ray tube utilizing electrostatic focus and magnetic deflection (114-degree diagonal deflection angle). It features a P4 aluminized screen, a spherical gray faceplate with 76% light transmittance, and a non-ion trap gun. Operating at a typical anode voltage of 18,500 V, it requires a 6.3 V heater and uses the 8HR basing configuration. Proper circuit design requires adhering to the minimum protective resistances on Grid No. 2 and Grid No. 4, as well as staying within the Design Maximum System limits.
