Hi John,
A long time after your request (only just seen it), but just in case you missed it - the info you are looking for is on my 1778 Yahoo group - Chapter 12. There's a colour pcb layout and colour annotated circuit diagram on there.
For other 1778 owners, the group contains both Service Manuals and the User Guide and can be downloaded either as individual chapters or (via a link) in 2 large chunks.
David, G4IRQ
http://groups.yahoo.com/group/RA1778/