19CG3 — Half-Wave Vacuum Rectifier

The 19CG3 is a duodecar-type half-wave vacuum rectifier designed primarily for service as a damper diode in the horizontal-deflection circuits of both color and black-and-white television receivers. It features a single heater-cathode structure housed in a Compactron T-9 glass envelope. The 19CG3 is electrically identical to the 6CG3 and 25CG3, differing only in its heater ratings and characteristics.

Heater Characteristics and Warm-Up

The 19CG3 is designed for series-string heater applications. It incorporates a controlled warm-up time to ensure reliable operation in series-connected heater chains.

The average heater warm-up time is defined by a standardized test condition. This is the time required for the voltage across the heater to reach 80% of its nominal (bogey) value after applying four times the bogey heater voltage (76.0 V) to a circuit consisting of the tube heater in series with a resistance equal to three times the bogey heater voltage divided by the bogey heater current:

$\text{Series Resistance} = 3 \times \frac{19.0\text{ V}}{0.6\text{ A}} = 95\ \Omega$

Physical Construction and Basing Configurations

The 19CG3 is constructed in a Compactron T-9 glass envelope with a button 12-pin base (E12-70), requiring a standard duodecar 12-contact socket. The physical dimensions of the tube are:

• Maximum Diameter: 1.188 inches
• Maximum Seated Height: 3.000 inches
• Maximum Overall Height: 3.375 inches
• Outline Designations: Section 8F, Section 8G, or Outline 9-62

Pinout Variations

Depending on the manufacturing standard and historical documentation, three distinct pinout configurations (basing diagrams) are associated with the 19CG3. These are designated as 12FX (with two documented variations) and 12HF.

Note on Internal Connections (IC): Pins designated as Internal Connection (IC) must not be used for external circuit connections. Leaving these pins entirely free of external wiring is critical to maintaining physical and electrical interchangeability with other tubes.

Electrical Characteristics and Capacitances

The 19CG3 features a coated unipotential cathode. The direct interelectrode capacitances of the tube, measured without an external shield, are:

• Cathode to Plate and Heater: 16.0 pF
• Plate to Cathode and Heater: 13.0 pF
• Heater to Cathode: 4.0 pF

Tube Voltage Drop

The internal resistance of the diode is characterized by its instantaneous tube voltage drop under high-current conditions. Depending on the specific manufacturer's production run, the typical instantaneous voltage drop is documented as:

• 20 V at an instantaneous plate current ($I_b$) of 700 mA
• 25 V at an instantaneous plate current ($I_b$) of 700 mA

Maximum Ratings (Design-Maximum System)

The ratings of the 19CG3 are established under the Design-Maximum System for operation in a 525-line, 30-frame television system. These ratings represent the limits within which the tube can be operated safely without degrading its reliability or service life.

Damper Service Ratings

• Peak Inverse Plate Voltage: 5000 V (absolute maximum)
  • Pulse Duration Constraint: The peak inverse voltage pulse must not exceed 15% of one horizontal scanning cycle, or a maximum duration of 10 microseconds.
• Steady State Peak Plate Current: 2100 mA
• DC (Average) Plate Current: 350 mA
• Plate Dissipation: 6.5 W

Heater-Cathode Voltage Limits

Because the cathode of a damper diode experiences high pulse voltages during horizontal retrace, the insulation between the heater and cathode is subjected to severe electrical stress. The 19CG3 is rated to withstand the following heater-cathode potentials:

• Heater Negative with Respect to Cathode:
  • DC Limit: 900 V
  • Total DC and Peak (Pulse) Limit: 5000 V
• Heater Positive with Respect to Cathode:
  • DC Limit: 100 V
  • Total DC and Peak (Pulse) Limit: 300 V

Technical Summary

The 19CG3 is a specialized duodecar-type half-wave vacuum rectifier designed for demanding damper diode service in television horizontal-deflection circuits. Operating with a 19.0 V, 0.6 A heater featuring a controlled 11-second warm-up time, it is optimized for series-string heater configurations. The tube is capable of handling a peak inverse plate voltage of 5000 V and a steady-state peak plate current of 2100 mA, with a maximum plate dissipation of 6.5 W. Its physical construction in a Compactron T-9 envelope and its high heater-to-cathode insulation ratings make it a robust component for high-voltage pulse applications.