The PCL86 was designed for the audio stage of a television receiver and offered a quality output.
In 1961 Mullard had developed a combination of an ECC83 triode and an EL84 output pentode in a single envelope and this was the ECL86. The PCL86 was the series heater chain version of that work.
The separate triode section would provide the first audio amplification, and the output pentode would drive the loudspeaker.
The PCL86 as a single ended audio amplifier would have a cathode resistor of 125 Ω and an anode load of 5,100 Ω and under these conditions would produce an output power of 4.1 Watts at a distortion of 10%.
The triode at the front with the electrostatic screen between it and the pentode.
The pentode with the screen continuing above the top mica.
The thin glass tube envelope is 21 mm in diameter and, excluding the B9A base pins, is 68 mm tall.
References: Data-sheet & 1040. Type PCL86 was first introduced in 1961.