Historic Transistor Photo Gallery

Photo Essay – Bell Labs Type A


Insulating Plug (Unbent leads)


.005 Phospor Bronze Point Contact Wires





Type A



Photo Courtesy Bob McGarrah


Photo Essay Commentary

Bell Labs developed model displays of the components of the Type A transistor, shown in the sequence of required manufacturing processes.  In the photo above, text has been added to label key components.  This particular model shows the insulating plug in two versions- with unbent leads (labeled in the photo) and also in a version with a bent right lead.  Here is a brief description from [2] describing the assembly process:  “…a slice of germanium cut from a high-back-voltage ingot is ground, copper plated and tinned on one side, and diced into small squares with a diamond wheel…..The .005 inch phosphor bronze wires, which previously had been pointed at one end by bevel-grinding and polishing, are spot welded to the end of these pins…..An additional .002 inch push compresses the springs enough to insure that the contact will be permanent under conditions of ordinary use….The cartridge then is wax-filled to improve its mechanical stability…..”  By any estimation, this is a mechanically intensive process and could be expected to yield devices with widely differing performance parameters.  


Go To PhotoGallery Type A Page 4



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