reseat all socketed chips first. if it works again, you're done. if it doesn't still, you will now need to pull the chips (work them out one side at a time as evenly as possible), if the legs of the chips look anything but shiny silver, you'll need to probably clean them up with fine sandpaper. you have to do this without breaking any of the legs off though.
this looks like a Z80 CPU thing though, I would start there first.
I would encourage testing voltage at one of the smaller ICs. (if you don't know how I have a picture that shows where to test in the PSU guide in my signature) if your +5 is morbidly low, then you'll probably need to focus on the fuse holders. the originals are made of galvanized steel and are 100 years old now, they're probably rusted or oxidized to oblivion.
also check that the edge connector isn't torched. the fuse issue will cause the edge to burn up. if you still have a filter board between the harness, remove it.