MANUFACTURING THE 300B VACUUM TUBE



Making the 300B. Making History.

Electron Valve offers an inside look at the manufacturing of 300B Vacuum Tubes at Western Electric in Kansas City.


It all started here a long time ago. These are some of the original Western Electric Drawings from the Western Electric engineers. These date back to the early 1940's when they made the 300A!


Today, many of the processes are the same and many have been updated. All parts are cleaned, heat treated and stored until needed. In the case where very low conductive water is needed for cleaning, de-ionized water is used. Click here to see a picture of the polishing pumps under the Kansas City Works. These pumps effectively remove all conductivity from the water.


Some of the parts require cleaning at very high temperatures in the "Hydrogen Atmosphere Furnace".


The process of assembling the many parts of the tube then begins. The grid is wound using one of the original winders built in 1943. This particular unit was made by RCA for Western Electric.


Here the grid is cut into three separate grids. Each one, if it passes inspection, will go into the 300B tube.


Each grid is hand inspected before being placed into the grid tray. Immense experience is necessary for precise and reliable grids. The man operating this grid winder has over 30 years with Western Electric grid windings.


All of the glass parts needed to make the Western Electric 300B are made right here at the plant. Here we see tubing as it is extruded into the flaring machine. The glass is heated to melting point and the machine spins the flare out. This flare, along with stem and other glass parts, will eventually become the base of the mount (More on that later).


Most of the metal parts of a tube have to be welded to the stem. A tweezer weld, made for Western Electric, is used to do this. Notice the Western Electric placard on the side of the welder.


Now, we are ready to form the mount. The mount is the part in the Vacuum Tube that actually does the work. It is the electronics of the tube. Here we see a skilled, long-time Western Electric worker begin assembly of the mount. The first step is to add the bottom mica.


The filament production is a very special and secretive process that gives Western Electric tubes their long life and reliability; therefore we could not photograph any of that process. The filament is coated with a proprietary chemical via a special system and taken up onto a large reel. To the stem, this filament is welded. The grid is then carefully tack welded into place and the plate is placed over the grid and welded into place.


The top mica is placed on and the final welds are made.


We now have a completed mount that is ready to be placed into mount trays.


Completed mounts are placed into trays and stored until they are ready to be joined with the envelope.


The mount and raw envelope are joined together to form the un-evacuated tube. Here we see Charles Whitener, CEO of Western Electric Export Corporation, on the line assisting a long-time Western Electric glassworker.


Here is where art meets science. The mount and envelope are placed into the machine. The glass is slowly heated as the tube is continually turned. As you can see in frames 1 through 6, the glass slowly melts and forms a perfect seal around the mount.


After the mount has been sealed to the envelope, it is placed into a tray to await the next step in the process. Again, there are alot of Western Electric secrets in this process, so we were not allowed to photograph this process either. The un-evacuated tube is placed into proprietary induction furnaces to heat the internal parts to several hundred degrees. The gas is evacuated from the envelope. The tube is tipped off (the evacuation tube is sealed). Western Electric vacuums are higher than any other 300B on the planet. This process not only removes the gas from the envelope, but also activates the filament so that it may begin to emit electrons.


Here we see the evacuated tube being "flashed". This is an induction process by which RF is run through the coils around the tube. The getter ring is excited and releases its material onto the inside of the envelope to form the silver getter.


This is the tube after it has been flashed.


The bases are pre-glued and readied for the insertion of the leads. This process forms the base / envelope shape we all know.


The wire leads from the tube are inserted into the pre-glued base and the tube is placed into the basing oven where the envelope and base are permanently joined.


Solder is applied to the pins to make the electrical connections secure.


The tube is now complete. The last step, before the electrical tests, is the final visual inspection. A long-time Western Electric employee performs this inspection. If there are any visual faults at all, the tube is rejected.


The tube is now ready to be aged to further activate the cathode. They are placed into ageing racks, where the filaments are brought to voltage and B+ voltage is applied to the anode (plate).


The light bulbs you see behind the tubes indicate tube healthiness. If a lamp is low or not on at all, the tube is immediately rejected. From here, the tube is fully analyzed by proprietary testing equipment. Once quality testing is complete, the tube is assigned a serial number, packaged and ready to be shipped.


The amount of care and attention to detail found at this plant is absolutely amazing. These tubes are actually built better than the older 300Bs. To my surprise, some of the manufacturing processes are greatly improved, making for a more consistent product. The upcoming tubes from Western Electric are the 274B, KT88 (GOLD LION), and 308A among others.


Charles G. Whitener has not only maintained the tradition of quality at Western Electric, but has improved upon it. There is no better 300B anywhere.