Here's the link: http://pictures.olsenstoy.com/library.htm
Unfortunately, I couldn't access the site this morning (not uncommon on weekends). When it's up, enter the library and look for the transformer listings.
IIRC, excessive hum is caused by a loose coil and laminated stack asssembly. The same problem was found with KW transformers. Both units were changed to riveted assemblies (the KW in 1957). Access the KW service section of the site for further information.