A big thank you captain bonkers, I know this thread is seriously old but I am facing the issue of having to build a PSU for this unit. I have a 9-0-9 transformer and understand nearly all of your explanations but I would like to ask if you could clarify the pin connections from the secondary, if I am understading you correctly you are saying that the:
1st phase output from the secondary 0v goes to pins 1,2
1st phase output from the secondary 9v goes to ping 3,4
2nd phase output from the secondary 0v goes to pins 5,6
2nd phase output from the secondary 9v goes to ping 7,8

Im hoping you or someone more enlightened can point me in the right direction.