I highly doubt you will find one.
I contacted Audio Control about 4 years ago trying to find diagrams so I could repair a SA-3050A RTA I had picked up, they would not release the diagrams for it (they were helpful in other ways though), I ended up reverse engineering the relevant parts myself (along with some photos provided by others of different versions and their reverse engineering also), I did a couple of videos about it, but that is obviously not relevent to your unit.