19DEP4 — Electrostatic Focus Cathode Ray Tube
The 19DEP4 is a 19-inch rectangular glass cathode ray tube (picture tube) designed for television display applications. It features electrostatic focusing and magnetic deflection, utilizing a short-neck design to minimize overall cabinet depth. The tube incorporates an aluminized fluorescent screen to maximize light output and prevent screen charging, alongside a non-ion trap gun design.
Physical Construction and Envelope
The 19DEP4 is constructed using a J149-A1 glass bulb envelope. The faceplate is made of spherical gray glass with approximately 78% light transmittance at the center, which helps improve picture contrast under ambient light.
The physical dimensions and alignment specifications are as follows:
- Overall Length: 11 7/8 ± 1/4 inches
- Neck Length: 4 5/8 ± 1/8 inches
- Deflection Angles (Approximate): Diagonal 114°, Horizontal 102°, Vertical 87°
- Bulb Contact: JEDEC No. J1-21 recessed cavity contact (Anode terminal)
- Bulb Contact Alignment: The anode contact aligns with Pin No. 4 within ± 30 degrees.
- Base: JEDEC No. B7-237 or B7-208
- Basing Configuration: 8HR
The tube is equipped with an external conductive coating. When properly grounded, this coating serves as a filter capacitor in conjunction with the internal anode.
Heater Ratings and Pinout
The 19DEP4 is designed with an indirectly heated cathode. The heater is engineered with a controlled warm-up time for use in series-string or parallel receiver designs.
The 8HR basing diagram provides the following pin connections, viewed from the bottom of the base:
Interelectrode Capacitances
The direct interelectrode capacitances of the 19DEP4 are approximately:
- Cathode to all other electrodes: ~5 μμf
- Grid No. 1 to all other electrodes: ~6 μμf
- External conductive coating to Anode: 1000 pF (μμf) minimum / 1500 pF (μμf) maximum
Absolute and Design-Maximum Ratings
The following ratings are established under the Design Maximum System. All voltages are measured with respect to the cathode unless otherwise specified.
Heater-Cathode Voltage Limits
- Heater negative with respect to cathode:
- During the equipment warm-up period (less than or equal to 15 seconds): 410 V maximum.
- After equipment warm-up is complete: 300 V maximum.
- Heater positive with respect to cathode: 180 V maximum.
Typical Operating Conditions (Cathode Drive Service)
Under typical operating conditions in cathode drive service, the operating parameters are defined as follows:
- Anode Voltage: 18,000 V DC
- Grid No. 4 Voltage (Focusing Electrode): 250 V DC (Individual tubes focus satisfactorily within a range of 0 V to 500 V DC)
- Grid No. 2 Voltage: 300 V DC
- Cathode to Grid No. 1 Voltage: 36 V to 54 V DC (required for visual extinction of the focused raster)
Maximum Circuit Values
To ensure safe operation and protect the tube from internal arcing or damage, the following circuit resistance limits and recommendations must be observed:
- Grid No. 1 Circuit Resistance: 1.5 MΩ maximum
- Grid No. 2 Circuit Resistance: 0.1 MΩ minimum
- Focusing Electrode Circuit Resistance: 0.1 MΩ minimum
Note: It is recommended to include protective resistance in the Grid No. 2 and focusing electrode circuits to prevent damage during transient conditions.
Related Designations
The 19DEP4 is closely related to the 19CKP4. The 19CKP4 is identical to the 19DEP4 except that the 19DEP4 is designed with higher Grid No. 2 and cut-off voltage ratings.
Technical Summary
The 19DEP4 is a 19-inch rectangular glass cathode ray tube utilizing electrostatic focus and a 114-degree magnetic deflection angle. It features a short-neck design (overall length of 11 7/8 inches), an aluminized screen, and a non-ion trap gun. Operating at a nominal heater voltage of 6.3 V, it is rated for anode voltages up to 22,000 V. The tube is optimized for cathode drive service, requiring a cathode-to-grid voltage of 36 V to 54 V for raster extinction under typical operating conditions.
