4HH Wiring Help

Hi All,
I have acquired a 4HH Sterling which has been somewhat abused by a previous owner, who fitted an aftermarket preamp and then attempted a rewiring job which went badly wrong (good news for me as I acquired it relatively cheaply). The issue i have is that i need to restore the wiring to standard but have been unable to find a suitable wiring diagram for a 4HH with a 5 position switch and 2 band preamp. Can anyone help?
Thanks