Vintage Radio Service Manual - KNIGHT model 4D-450  4-tube portable (battery operated) Superheterodyne AM radio receiver. Manufactured by Allied Radio Corp., of Chicago, IL. Dated 1948. 4 pages. Original old Sams Photofact manual includes schematic, layout, alignment instructions, dial cord drive, voltage & resistance test chart, repair parts list and description. This manual would make a sensational accompaniment to your retro audio equipment.