The Ediswan R-Type is the first production valve of the Great British Valve Project from Brimar Thermionic Products.
The valve was made using genuine original Ediswan equipment in 2025 over 100 years after the first production of Ediswan R Types. The vertical electrode assembly in the original valve was a step in the development of the tubular R Type known as the AR.
The serial number G20. The test certificate is below.
The electrodes are held in a pinch. The filament is a single strand tungsten wire that is clamped in folds of the supports - the tungsten melting point being too high to spot weld. There is no filament tension spring. The ring cup on the left is the getter holder.
Three spot welds close the folded anode and attach the rod support.
The control grid wire is fixed to a single support rod. The loops are held by notch and peen with the ends spot welded to the support.
The single filament wire with the top held in the support running outside the anode.
Simple brass split bins on the B4 base with wires soldered at the top. The base skirt is copper.
The lower end of the cylindrical anode showing the filament and grid loops.
The base and pinch.
The folded anode is spot welded to the support that also carries the getter holder.
The sequence of supports in the pinch.
The getter holder and the top of both filament and control grid.
The certificate of authenticity.
The balloon envelope is 55 mm in diameter, and excluding the B4 base pins, is 91 mm tall.
Reference: Data-sheet Type R Type was first introduced in 1916. See also1916 adverts.
