Well I got the AC-3 RF demodulator working.
This unit will let me record a laserdisc's 5.1 mix straight into my PC without having to down mix into Stereo. I'll now be able to turn these mixes into DTS lossless files for my preservation projects.
I posted the solution to my problem over on my classic Bond laser preservation thread.
http://originaltrilogy.com/forum/topic.cfm/Bond-Laserdisc-Preservations-1962-1971/post/443970/#TopicPost443970
FF