Vintage Radio Service Manual - AIR CHIEF model 4-C-5 (Code No. 291-7-574) AC-DC portable (battery-line operated) 4-tube AM radio receiver. Manufactured by Firestone Tire & Rubber Company, of Akron, OH. Dated 1948. 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.