19CS4 — Efficiency Diode

The 19CS4 is an indirectly heated efficiency diode designed primarily for series-heater operation in AC/DC television receivers. It is electrically equivalent to the U191 and is engineered to withstand the high-voltage pulses typical of television line-scan circuits.

Physical Characteristics and Base Connections

The 19CS4 features a clear glass bulb with a top cap connection and is mounted on an International Octal (IO5) base. The tube can be operated in any mounting position.

Physical Dimensions and Weight

• Maximum Overall Length: 90 mm
• Maximum Seated Height: 77 mm
• Maximum Diameter: 32 mm
• Approximate Net Weight: 1.25 oz
• Approximate Packed Weight: 2.25 oz

Pin Configuration

The base connections utilize the International Octal configuration, with the cathode brought out to a top cap (CT1) to maximize insulation against high-voltage pulses.

Note: When the anode is subjected to pulsed operation, it is recommended to remove contacts 1 and 6 from the valve holder to prevent voltage breakdown or unwanted coupling.

Heater and Interelectrode Capacitances

The heater is designed for series-string operation in television receivers, drawing a constant current.

• Heater Voltage ($V_h$): 19.0 V
• Heater Current ($I_h$): 0.3 A

Interelectrode Capacitances

The capacitive coupling between electrodes is kept low to ensure stable operation in high-frequency scanning environments:

• Anode to Heater plus Cathode ($C_{a-h,k}$): 7.7 pF
• Cathode to Heater plus Anode ($C_{k-h,a}$): 9.0 pF

Operating Ratings and Limits

The 19CS4 is rated under the Design Centre System, with specific absolute maximum limits defined for television line-scan service (defined by a duty cycle of 15% or less and a pulse duration not exceeding 15 \mu s).

Voltage Ratings

• Maximum Peak Inverse Anode Voltage (P.I.V. max): 4.5 kV (Design Centre Rating) / 5.3 kV (Absolute Maximum Limit under TV Line Scan conditions).
• Maximum Heater-Cathode Voltage ($V_{h-k(\max)}$) (heater negative, DC + Peak AC): 900 V, measured with respect to the higher potential heater pin. The DC component of this voltage must not exceed 600 V.
• Maximum Heater-Cathode Voltage ($V_{h-k(pk)\max}$) (heater negative, pulse): 4.5 kV (Design Centre Rating) / 5.3 kV (Absolute Maximum Limit under TV Line Scan conditions).
• Maximum Heater to Anode Voltage ($V_{a-h(\max)}$) (heater positive pulse): 3 kV (Absolute Maximum Limit under TV Line Scan conditions).

Current Ratings

The tube's current-carrying capacity is specified in paired combinations of mean and peak anode currents:

• Option 1: Maximum mean anode current of 120 mA paired with a maximum peak anode current of 600 mA.
• Option 2: Maximum mean anode current of 150 mA paired with a maximum peak anode current of 450 mA.

Electrical Characteristics and Curves

The forward conduction characteristics of the 19CS4 show low internal resistance, allowing high current flow with minimal anode voltage drop. The relationship between anode voltage ($V_a$) and anode current ($I_a$) is characterized by the following typical operating points:

• At an anode voltage of 10 V, the anode current is approximately 150 mA.
• At an anode voltage of 20 V, the anode current rises to approximately 380 mA.
• At an anode voltage of 30 V, the anode current reaches approximately 640 mA.
• At an anode voltage of 40 V, the anode current is approximately 920 mA.

Technical Summary

The 19CS4 is a specialized efficiency diode (equivalent to the U191) designed for series-string television receivers. Operating with a 19.0 V, 0.3 A heater, it features an International Octal base with a top-cap cathode connection to handle high pulse voltages. It supports peak inverse voltages up to 5.3 kV and peak anode currents up to 600 mA under pulsed line-scan conditions. Its low forward impedance ensures highly efficient operation in television horizontal deflection circuits.