FWIW, here's a thermography (hope the link works) of the B-cache section
 of the KA-675 after being powered up for ca. 30 mins:
 
https://www.dropbox.com/s/2nsx1dfngp1jfq5/TH710065.BMP?dl=0
 Note that the rightmost chip just below the CPU heatsink has a pin that's
 ca. 2 degrees warmer than the others. I don't know if that says anything,
 but it *is* reproducible. Maybe I should start with that one.
 
I can't really make it out on the image but if it is just one pin that is
hot, maybe there is nothing more complicated wrong than a bad solder joint
at that pin, particularly if it is a power or ground pin.
Regards,
Peter Coghlan