You could try Organ Service Corporation <OrgSvcCorp@aol.com>, P O Box
372, Marengo IN 47140-0372; tel 1-800-457-4408.  They bought out the
Conn Organ and Strobe parts inventory.  I got an ST-11 strobe schematic
and owners book from them.

Note: the ST-6 models will drift as you use them.  You have to check
the calibration every 5 minutes or so, to be sure you are on the money.

Scott Olson
Missoula, Montana