Here is a collection of PDF manuals, various mods, both military and civilian, and a collection of e-mail archives on the Hammarlund SP-600, both -JX and VLF-31 versions.

1) SP-600 Maintenance Manual

2) SP-600 Overhaul Manual

3) SP-600 Parts Manual

4) SP-600 Service Manual

5) SP-600 VLF-31 Manual

More later...