The ESW20 from Ediswan was described as replacing the Taylor Tubes T20 and having the same characteristics. In the absence of the correct data, the above is copied from the T20.
These valves were used for Class C RF amplifiers and (in pairs) also Class B modulators.
An extract from an advert in Short Wave Magazine (May 1938) reads: From May the 1st Taylor T20 and TZ20 will be increased in price to I7/6.
The new Ediswan British-made ESW20 which supersedes the above tube, with identical characteristics, now available at 17/6.
Webb: intend to support British Manufacturers catering for the Amateur.
The anode from the side. The ceramic insulators point to high anode voltages. The filament spring at the top is the remaining one of a pair. The broken filament was M shaped.
The anode is carbonised for better heat radiating efficiency and ribbed for rigidity of the thin nickel plate.
A closer view: the remains of the filament can be seen. This would have been thoriated tungsten wire. The filament support spring has a hook at the lower end to hold the filament.
The balloon envelope is 58 mm in diameter and, excluding the UX4 base pins, is 146 mm tall.
Reference: Television Magazine, May 1938. Type ESW20 was first introduced in 1938. See also1938 adverts.
