The EL505 is output pentode designed for TV line deflection circuits. The EL505 differs from the PL509 in not only having a 6.3 Volt heater but also that the anode dissipation is 25 Watts not 30. The PL505 has a 300 mA heater.
This was one of the last TV line timebase output pentode valves to be designed. These valves were designed for service in colour television receivers employing shadow mask tubes.
The normal anode voltage of 160 Volts is designed to be exceeded by pulses of up to 7,000 Volts and 1.4 Amps.
Radio amateurs also used such valves, known in America as 'sweep tubes' for short-wave transmitters, sometimes with the valves in parallel to increase the power available.
The construction is as a beam tetrode and the bright beam plate can be seen as can the inner grids. The heatsink on the top of the control grid supports is large.
Extra metal is present in the centre of the anode working face to aid heat radiation.
The wide glass tube envelope is 38 mm in diameter and excluding the B9D base pins, is 114 mm tall.