AN/ARC-102 Radio Set, Operator's and Repair-Parts/Diagrams Manuals: $13
     294 pages in three manuals.
     Covers RT-698/ARC-102 Receiver-Transmitter (Collins 618T-3),
     C-3940/ARC-94 Radio Set Control (Collins 714E-3), and
     PP-3702/ARC-102 Power Inverter/Mounting (Collins 3905-2).
     Includes Operator's and Organizational Maintenance Manual, Operator's and
     Organizational Repair-Parts Manual, and Depot Repair-Parts (and diagrams) Manual,
     with exploded views and all board/component-layout diagrams and parts lists.
     No schematics. 

http://www.fullnet.com/u/tomg/manuals.htm

See also: http://www.qsl.net/vk4czt/618t.htm

Also see Letter on the 618 series