Vintage Radio Service Manual - AIR CHIEF model 4-A-27 (Code No. 297-7-RN228) 5-tube Superheterodyne AM radio receiver. Manufactured by Firestone Tire & Rubber Company, of Akron, OH. Dated 1947. 4 pages. Original old Sams Photofact manual includes schematic, layout, alignment instructions, voltage & resistance test chart, repair parts list and description. This manual would make a sensational accompaniment to your retro audio equipment.