Oldtimer Cameras of Hatfield, England, should be able to provide you with a Pentacon Six camera and/or prism service manual.  Their website is www.oldtimercameras.com. 
e-mail sales@otcworld.co.uk
Tel +44 1707 273773 (9.30 to 5.00 Monday to Friday)
Even if you can’t find the manual on the website, you can order it.  (You can’t consult it online.)

The link provided in February 2010 to an on-line copy of the service manual unfortunately no longer works (March 2013).  However, Oldtimer Cameras of England (link above) do - to the best of my knowledge - still offer the full range of their publications.  (I regularly receive e-mails from them.)

You can see exploded diagrams of the camera and the TTL metering pentaprism here.  There are contact details for repairers here.