Perhaps the PIA pin(s) itself were corroded not the socket, hence the problem going away when the chip was swapped...
You could be right Marty, when I swapped the chips the board booted, I then swapped them back to their original position and the fault re-occurred.
If the U10 socket was bad then it would have had trouble with the chip from U11, unless it is some weird combo of partly bad socket and partly bad chip???
The chip from U11 was newer so maybe the legs were cleaner than the older chip from U10.
Anyway I will definitely be writing this one down for future reference.
