Check this : https://www.manualslib.com/manual/724874/Mackie-8-Bus.html#manual
there is also a thread on this on GR

I remember doing minor repairs on different Mackie mixers over the years. I'm not 100% sure about the 32•8 , but it was always my impression that disassembling one completely meant removing every knob and all the nuts on the stem of every pot (plus just a handful of screws). I think one of the ways they achieved the level of performance they got at that price point was by using monolithic circuit boards. (as opposed to every channel having its own) I wouldn't be surprised if the 32x8 had one big pcb for the master section (Mains and Subgroups) + channels 17-32, plus another one for channels 1-16 - or possibly in increments of 8. That way they could assemble either a 16•8, a 24•8, or 32•8 with the same 2 or 3 pcbs.