Vintage Amplifier Service Manual - THORDARSON model T-31W10A 7-tube public address audio amplifier. Manufactured by Thordarson Electronics Manufacturing, div of Maguire Industries, Inc., of Chicago, IL. Dated 1947. 4 pages. Original old Sams Photofact manual includes schematic, layout, voltage & resistance test chart, repair parts list and description. This manual would make a sensational accompaniment to your retro audio equipment.