According to Frank Hood, in his Tektronix, The Early Days, recollection:
We were having a great deal of trouble in getting dependable suppliers of some of our components. Gordon Sloat, who had had experience in winding transformers was hired to set up a department to make our own transformers.
We don't know the exact date of when the Transformer Department was formed, but likely around 1950. This November 1951 TekTalk article features the transformer employees who worked on swing shift so the department had grown considerably by this time.
This February 1952 TekTalk features a notice for Transformer School.
The 1952 Tektronix Catalog contains this information on the lifetime warranty for transformers. This warranty was rescinded in the early 1970s due to lack of replacement availability.
The 1955 Employee Photo Album lists 25 employees. Click on the image to view the PDF.
The 1958 Employee Photo Album shows the group has nearly doubled to 45 employees and the department name now includes "Coils". Click on the image to view the PDF.
The Transformers and Coils department was spun out of Tektronix as Multicomp Inc. in 1986.