The service manual for the 4016 / 4032 can be had from the redoubtable zimmers website here:-
https://www.zimmers.net/anonftp/pub/cbm/schematics/computers...s_4016-4032_Technical_Reference.pdf
However there are three distinct sets of diagrams in that manual so Colin, could you please remind us which set of diagrams in the manual applies to your mainboard?