14Y4 — Full-Wave High-Vacuum Rectifier
The 14Y4 is a locking-in (Loctal) eight-pin, full-wave, high-vacuum rectifier tube designed for power supply applications in electronic equipment. It features a coated unipotential cathode and is designed to operate under a range of heater voltages, with a nominal rating of 14.0 V and typical operation at 12.6 V. The tube is capable of delivering a maximum DC output current of 70 mA and can withstand a maximum peak inverse voltage of 1250 V.
Physical Specifications and Basing
The 14Y4 is constructed in a T-9 glass bulb with a locking-in 8-pin base. Its physical dimensions are:
- Maximum Diameter: 1 3/16 inches
- Maximum Overall Length: 2 25/32 inches
- Maximum Seated Height: 2 1/4 inches
The tube is designed to be mounted in any position.
Pin Connections
The 14Y4 utilizes the RMA Basing No. 5AB-L-O (or 5AB) connection scheme. When viewed from the bottom of the base, the pin assignments are:
Heater Characteristics
The 14Y4 features a coated unipotential cathode. The heater can be operated from either an AC or DC supply. The tube has two sets of heater specifications depending on the operating context:
This dual-voltage capability allows the tube to be used in nominal 14.0 V electrical systems (such as automotive systems under charge) as well as standard 12.6 V heater circuits.
Maximum Ratings and Electrical Characteristics
The absolute maximum ratings for the 14Y4 under rectifier service are:
- Maximum Peak Inverse Voltage: 1250 V
- Maximum DC Heater-to-Cathode Potential: 450 V
- Maximum Steady-State Peak Plate Current (per plate): 210 mA
- Maximum DC Output Current: 70 mA
Tube Voltage Drop
The internal voltage drop of the 14Y4 is relatively low for a high-vacuum rectifier. Measured with an applied DC current of 70 mA per plate, the tube voltage drop is 22 V.
Typical Operating Conditions
The 14Y4 can be operated in full-wave rectifier circuits using either condenser-input (capacitor-input) or choke-input filter configurations.
Condenser Input to Filter
Under condenser-input conditions, the typical operating parameters are:
- Heater Voltage: 12.6 V
- Heater Current: 0.300 A
- AC Plate Voltage per Plate (RMS): 325 V (Maximum)
- DC Output Current: 70 mA (Maximum)
- Total Effective Plate Supply Impedance per Plate: 150 ̩ (Minimum)
Impedance Note: When filter condensers larger than 40 µF are used, it may be necessary to add additional plate supply impedance to limit peak currents and protect the tube.
Choke Input to Filter
Under choke-input conditions, the typical operating parameters are:
- Heater Voltage: 12.6 V
- Heater Current: 0.300 A
- AC Plate Voltage per Plate (RMS): 450 V (Maximum)
- DC Output Current: 70 mA (Maximum)
- Minimum Value of Input Choke: 8.0 H
By using a choke-input filter, the allowable maximum AC plate voltage per plate is increased from 325 V RMS to 450 V RMS, while maintaining the same maximum DC output current of 70 mA.
Technical Summary
The 14Y4 is a locking-in, full-wave high-vacuum rectifier tube featuring a coated unipotential cathode. With a nominal heater rating of 14.0 V / 0.320 A (and a typical operating point of 12.6 V / 0.300 A), it is well-suited for compact or mobile power supplies. It supports a maximum peak inverse voltage of 1250 V, a peak plate current of 210 mA per plate, and a continuous DC output of 70 mA. Its low voltage drop of 22 V at 70 mA ensures efficient power conversion in both condenser-input (up to 325 V RMS per plate) and choke-input (up to 450 V RMS per plate) filter configurations.
