I say, we are now on the home straight here with the final episode in our tale of a globetrotting 1950s newspaper reporter's visit to Mullard Blackburn: -
In the Grid Department, the grid backbones were being fed through a machine from reels and the tungsten wire, fitted on to a spool was wound around these backbones. The grids, up to now all bound together in one continuous strip, were later cut into single units and connections welded to them in readiness for assembly in the valve base.
The next part of the tour included the Glass Factory where I wished I had discarded my scarf as the furnaces were blazing away at 1200 degrees Centigrade. From the furnaces emerged glass tubing of varying diameter which was fed vertically in an unending cylindrical shape up through two floors to the cutting machines.
After seeing the tubes disappear through the "grill room' ceiling we then followed them to a part of the factory where the traditional art of glass blowing by power of lungs and skill of eye was neither welcome nor respected. Indeed, I should have pitied the consciencious craftsman who would have the awesome task of keeping pace with the relentless flow of tube from the furnaces below.
Two methds of cutting the tube were in use with the first using a thin band of heat and a cold wheel to effect a break which was then smoothed by application of a flame. A mechanical pair of hands sealed off the end and heated air blew it into the desired size and shape. The second saw a diamond doing the preliminary work finished off by a fire jet. Bases were also being rolled off an assembly line at this factory, the capacitoy of one base pressing machine alone being 2000 an hour.
At last to the assembly unit or Valve Making Department. Here assemblers fit together a 40 or 50 piece jigsaw in a foot operated jig. Some of the jigsaw parts are so small that they have to be lifted from their racks by magnets which the assemblers wear on their hands like rings. The bench layout is so constructed such that left and right hands are kept fully employed. Not an instant is wasted. An electric spark welds on the base in a twinkling of the eye.
On the "ageing rack" tests are carried out under much more severe conditions than the valve would ever experience in Mr & Mrs Smith's TV set. The valves are now ready for packing and loaded on the long bay at the rear of the factory where a van fleet is kept busy throughout the day. I took leave of my hosts as one of Mullard's 200 internal telephones summoned them to some distant part of the factory.