19Y3 — Half-Wave High-Vacuum Rectifier

The 19Y3 is an indirectly heated half-wave high-vacuum rectifier designed primarily for series-connected heater strings in television and radio receivers. Housed in a miniature glass envelope with a nine-pin base, it provides reliable high-voltage rectification with moderate current capabilities.

Physical Construction and Basing

The 19Y3 features a miniature construction utilizing a T6½ glass bulb. It is designed to be mounted in any position. The physical dimensions of the tube are as follows:

The tube uses a small button noval 9-pin base with a JETEC 9BM basing designation. The pin connections, viewed from the underside of the base, are assigned as follows:

• Pin 1: Internal Connection (IC) / No Connection (NC)
• Pin 2: Internal Connection (IC) / No Connection (NC)
• Pin 3: Cathode
• Pin 4: Heater
• Pin 5: Heater
• Pin 6: Internal Connection (IC) / No Connection (NC)
• Pin 7: Internal Connection (IC) / No Connection (NC)
• Pin 8: Internal Connection (IC) / No Connection (NC)
• Pin 9: Plate (Anode)

Heater and Cathode Ratings

The 19Y3 is equipped with a coated unipotential cathode. The heater is specifically rated for series-string operation:

• Heater Voltage: 19 V
• Heater Current: 0.3 A (300 mA)

Due to its application in series-connected heater circuits, the tube is designed to withstand significant potential differences between the heater and the cathode. The maximum heater-cathode voltage ratings are defined as:

• Peak Heater-Cathode Voltage (cathode positive with respect to heater): 550 V
• Peak Heater-Cathode Voltage (heater negative): 550 V (applicable with a mains voltage of 220 V RMS or less, plus a maximum DC component of 250 V)
• DC Component of Heater-Cathode Voltage: 250 V
• AC Component of Heater-Cathode Voltage: 220 V (RMS)

Maximum Ratings and Operating Constraints

To ensure reliable operation and prevent damage to the tube, several limiting values must be observed during circuit design. These maximum ratings are specified for half-wave rectifier service:

• Maximum Peak Inverse Plate Voltage: 700 V
• Maximum RMS Supply Voltage: 250 V
• Maximum DC Output Current: 180 mA
• Maximum Filter Input (Reservoir) Capacitor: 60 µF

When two tubes are operated in parallel, the maximum reservoir capacitor limit may be increased to 100 µF, provided that each plate is connected with the minimum specified total effective supply impedance.

Minimum Supply Impedance Requirements

The tube requires a minimum total effective plate supply impedance (limiting resistance) to protect the cathode from excessive peak currents during turn-on and steady-state operation. This minimum resistance depends directly on the applied AC input voltage:

• 250 V RMS Input: 100 Ω minimum
• 240 V RMS Input: 80 Ω minimum
• 230 V RMS Input: 60 Ω minimum
• 220 V RMS Input: 40 Ω minimum
• 200 V RMS Input: 30 Ω minimum
• 127 V RMS Input: 0 Ω minimum

Typical Operating Conditions

The 19Y3 can be operated under several typical combinations of input voltage and supply impedance. In typical applications utilizing a 60 µF filter input capacitor, the tube delivers a highly consistent DC output voltage across a range of standard mains supplies:

At a standard DC output current of 180 mA, the typical tube voltage drop is 15 V.

Electrical Characteristics and Curves

The electrical behavior of the 19Y3 is characterized by its forward conduction and output regulation profiles.

Plate Conduction Characteristics

The plate current versus plate voltage relationship shows a typical diode forward conduction curve. Conduction begins immediately as voltage becomes positive:

• At 10 to 11 V of plate potential, the current reaches approximately 100 mA.
• At 18 V, the current rises to approximately 200 mA.
• At 20 V, the current is approximately 270 mA.
• At 25 V, the current reaches 300 mA.
• At 30 V, the current is approximately 470 mA, while reaching 400 mA at approximately 31 V.

Regulation and Output Performance

The DC output voltage versus DC output current curves demonstrate the regulation performance of the rectifier under load. As the output current increases from 0 to 200 mA, the output voltage exhibits a downward slope due to the internal resistance of the tube and the external supply impedance:

• With an AC input of 250 V RMS and a supply impedance of 125 Ω, the open-circuit output voltage starts at approximately 340 to 350 V at 0 mA.
• As the load increases, the voltage drops, converging to exactly 195 V at the rated 180 mA output current.
• Similar convergence behavior is observed across the 200 V to 240 V input range when paired with their respective recommended supply impedances, ensuring a stable 195 V output at full load.

Related Designations

The PY82 is a related rectifier type. In applications where two rectifiers are operated in parallel to achieve higher current capacity or larger reservoir capacitance (up to 100 µF), the operating guidelines and minimum limiting resistance per anode apply similarly to both the 19Y3 and the PY82.

Technical Summary

The 19Y3 is a miniature, indirectly heated half-wave high-vacuum rectifier featuring a 19 V, 0.3 A heater designed for series-connected operation. Housed in a T6½ bulb with a 9-pin noval (JETEC 9BM) base, it is capable of delivering up to 180 mA of DC output current with a maximum peak inverse plate voltage of 700 V. By adhering to the specified minimum plate supply impedance values (ranging from 0 Ω at 127 V to 100 Ω at 250 V), the tube provides reliable voltage rectification and stable output regulation in power supply applications.