This ECL80 is a British made triode, output pentode for audio use. The ECL80 is a low power device with the triode feeding the pentode for a compact single end audio stage.
The heater at 6.3 Volts and 300 mA makes this valve suitable for equipment with mains transformers and heater chains across the domestic mains.
Mullard describe the ECL80 as primarily designed for use in television receivers (VHF 405 line models) with the triode as a frame blocking oscillator and the pentode as a frame output valve. Other applications include the use of the triode as a line blocking oscillator, AF voltage amplifier or in multivibrator circuits and the operation of the pentode as an audio output valve or a synchronising pulse separator. This valve was also used in low cost record players with high output crystal pick-ups, normally with a metal rectifier. The latter being an early solid state device.
The ECL80 was not without faults in use and the above article gives details.
The triode is mounted above the pentode on the common cathode tube.
The suppressor grid is also wound on copper supports and can be seen to have a heat radiating fin positioned to the side of the triode. In this place it can also act as an electrostatic screen.
The ECL80 was popular for use in low cost record players and a typical circuit is shown.
The thin glass tube envelope is 20 mm in diameter and, excluding the B9A base pins, is 59 mm tall.
References: Data-sheet & 1040. Type ECL80 was first introduced in 1950.