The LS5 is a triode designed in 1923 especially for driving a loudspeaker and featured many developments in valve design. The LS5 had, for its day, a high anode dissipation of 10 Watts.
The LS5 was of the early dull emitter valves to be introduced by M-OV who were the first manufacturer to introduce thoriated tungsten filaments. This introduction followed intensive research from 1919 onwards. The use of the V shaped filament with tension spring was new as was the flattening of the anode cylinder and grid helix.
Initially these valves had a metal base skirt. The plastic base indicate later production.
The balloon envelope with the Osram name on the glass.
The control grid is wound on a looped support. The filament is a single inverted V.
Here the filament tension spring with filament retaining hook is clearly seen. The control grid supports are insulated from the filament support by being embedded in a glass bead.
The balloon envelope is 56 mm in diameter and, excluding the B4 base pins, is 108 mm tall.
References: 4051 & 1004 Type LS5 was first introduced in 1923. See also1923 adverts.
