The Type A from Siemens was developed from the French hard valve towards the end of 1917 after samples were captured. Like the earlier inefficient German valves (eg RJW) the workmanship is of high quality. Five basic designs were made: two designs from AEG, two designs from Telefunken and the Type A from Siemens and Halske.
The white logo on the two ends is the S with H of Siemens and Halske.
The construction has a single strand filament at one end with the grid and anode originating from the pinch at the other end. Note that in this example the glass separator has been broken. Probably due to an impact.
The anode and grid are partly in place, held by the metal connections, but the spacing is wrong due to the severed glass rod.
The anode/grid pinch stem.
The filament pinch stem.
The copper stranded wires from the glass are soldered to the spring connectors.
The metal parts are badly corroded.
The A and G are moulded into the base.
The moulded logo filled with white paint.
The corrosion looks like rust suggesting a compromised vacuum. The control grid is of the ladder form with individual wires fitted to flat end strips.
The corrosion on the grid wires is extensive.
Here the grid can be seen to have been punched from a flat sheet.
The filament is held in a fold on the support.
The anode to grid spacing is fixed by glass beads at the corners.
The wide glass tube envelope is 37 mm in diameter, and including the base pins is 107 mm tall.
References: Internet. Type Type A was first introduced in 1917. See also1917 adverts.
