102E Vacuum Tube
A triode vacuum tube designed for detector and amplifier service, featuring a high amplification constant and low-voltage filament operation.
Overview
The 102E (also designated as the 102-E) is a vacuum tube designed for use as a detector and an amplifier. It is engineered for compatibility with Western Electric Vacuum Tube Sockets Nos. 100-L or 100-R. The tube features a classic spherical bulb construction with a specialized four-pin bayonet base.
Physical Construction and Basing
The 102E is constructed with a glass envelope having a maximum bulb diameter of 2-3/8 inches and an overall height of 4-1/2 inches. The tube utilizes a cylindrical base equipped with a side-mounted locating pin (bayonet pin) to ensure correct orientation when inserted into its socket.
The base configuration consists of four pins on the bottom, arranged as follows:
- P: Plate (Anode)
- F+: Filament positive terminal
- F-: Filament negative terminal
- G: Control Grid
The locating pin is positioned on the side of the base adjacent to the filament-negative and grid pins.
Electrical Characteristics and Amplifier Operating Points
When operated as an amplifier, the 102E exhibits specific electrical parameters. The filament is designed for low-voltage, moderate-current operation, and the tube operates with relatively low plate currents and a high amplification factor.
Filament Ratings
- Normal Filament Voltage: 2 to 2.5 Volts
- Normal Filament Current: 0.95 Ampere
The filament current is a critical factor in determining the operating life of the tube. To ensure maximum useful life, the filament current should be maintained at the lowest possible level that still secures the desired output. Operating the filament above a current of 1.15 amperes will materially shorten the service life of the tube.
Amplifier Operating Parameters
Under normal operating conditions as an amplifier, the electrical characteristics are defined by the following ranges:
Circuit Applications and Variations
The 102E is versatile, serving as both a detector and an amplifier. While the standard electrical values and operating ranges listed above apply specifically to its use as an amplifier, these parameters are not rigid when the tube is employed in other roles.
When the 102E is configured as a detector or for alternative circuit applications, the applied voltages may be varied to suit the specific requirements of the circuit. Adjusting these applied voltages will result in corresponding variations in the other electrical values, such as plate current and plate-to-filament impedance, allowing the tube to be optimized for different operating conditions.
Technical Summary
The 102E is a detector and amplifier triode characterized by its physical dimensions of 2-3/8 inches in diameter and 4-1/2 inches in height, designed for Western Electric Nos. 100-L or 100-R sockets. It features a four-pin bayonet base with a locating pin. Electrically, it operates with a 2 to 2.5 V filament drawing 0.95 A normally, with a strict maximum limit of 1.15 A to prevent premature filament degradation. In amplifier service, it operates with plate voltages between 100 and 150 V (160 V maximum safe limit), grid bias of 0 to -3 V, and plate currents of 0.3 to 1.5 mA. It provides an amplification constant of 26 to 34 and a plate-to-filament impedance ranging from 40,000 to 100,000 ohms, with adaptable operating parameters when configured for detector applications.
