How this mod came to be.
How to make your HW8 Talk DSB
DSB PSK Notes
Photo 1 of mod
Photo 2 of mod
Photo 3 of mod
Photo 4 of mod
Photo 5 of mod

FYI: There is a partial manual and schematic for HW8's at:
ftp://bama.sbc.edu/downloads/heath/hw-8/ (busy site - keep trying)