The PL84 frame output pentode was designed for use in television receivers. 110° deflection picture tubes required considerable power to the deflection coils and the PL84 was designed for this service.
The PL84 is based on the EL84 audio output valve but designed for lower HT voltages. The data-sheet gives values for both single ended and push-pull amplifiers.
Through the holes in the anode can be seen the three wire grids.
The copper supports of the control grid are topped with small radiating fins. Most of the connections at the base are copper or copper tape. The heater is coiled as can be seen below the end of the insulation.
The thin glass tube envelope is 21 mm in diameter and, excluding the B9A base pins, is 71 mm tall.
References: Data-sheet & 1040. Type PL84 was first introduced in 1956. See also1956 adverts.
