The pictures in this article come from the BVWS DVD of the 1950s Mullard film.
To build the electrodes into the finished assembly took great dexterity, tweezers and a small support jig. The process started with the bottom mica into which was located the cathode. The grids were placed over the cathode in order from g1 to g3 before the anode was carefully placed in the bottom mica. The top mica was then placed and the electrodes moved about with the tweezers until all the protrusions passed through.
The cathode is inserted first followed by the three grids When the basic components are inserted between top and bottom micas the base and the electrodes are placed in a hand jig and the lid closed. The electrode supports are then spot welded to the support wires fixed into the base.
Views of the assembly jig
The jig has a set of holes for the pressed glass base to fit into. The top cavity is machined to hold and support the electrodes. When the top section is closed the operator pushes the base section into place to mate with the electrodes. Foot operated spot welding machines with specially shaped electrodes would then be introduced into the spaces in the jig to fix the components together.
Spot welding machines in use
The EF80 had the heater threaded through the cathode from the top after the main assembly was completed. After threading into place the heater wires would be spot welded to the base wire preformed to receive them.
Threading the EF80 heater into the cathode
Valve assembly in the 1950s was a very labour intensive process
Valve making originally was centred in the London area, but moved to other regions during WWII. As the textile manufacturing industries of Lancashire declined with foreign competition so the large skilled workforce of dextrous machinists formed a valuable pool of labour from which to recruit staff for the assembly processes of the electronics industries. The pictures of rows of valve assembly workers looks very similar to rows of garment machinists.