The ECL80 is a triode, output pentode for audio use. 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.
The ECL80 is a low power device with the triode feeding the pentode for a compact single end audio stage.
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 lower electrode structure is the beam tetrode, the triode is a 5 mm structure at the top of the valve.
The copper grid supports have cooling fins spot welded on.
Another ECL80 from Mullard
The triode at the top is clearly seen in this image. The grid extends beyond the anode and the copper rod is the connection to the triode anode.
The pentode electrodes are aligned at right angles to the triode section.
The thin glass tube envelope is 20 mm in diameter and, excluding the B9A base pins, is 58 mm tall.
References: Datasheet & 1040. Type ECL80 was first introduced in 1950.