99 percent of the time it is the PLA chip (primary logic array). If that isn't it usually ram. Then the 74lxxxx chips. The traces and pads on this thing would have made me give the customer a straight replacement and then fix the board in question over time. Kudos for doing the DIAG and fix to the end. Somebody in the past had an unsteady hand and tooooooo much heat on their iron. Also, who replaces a chip without socketing....