Hi RetroPin,
I got a bit keen tonite and wanted to see if replacing all the 4049's had worked. So, I scotchlocked the exposed G.I wires for bumpers & taped, double checked that nothing else was or could be exposed underneith then plugged display in & fired her up. To my surprise, all three are now working. I didn't run through the diagnostics as I didn't have enough hands but definately getting what appears to be correct on all!
Soo the good news is that it may look like the SRC's on CPU are healthy. I was still getting some 'flaming' on the top alpha display (not sure what the correct term is) but I would bet that it is caused by the unbalanced +100/-100.
So hopefully I can pickup my PinScore LED tomorrow & put that in. The better news is that this one survived and I've got a spare, or pick up a bargain somewhere (MarkC???!!) to put it in. Taxi maybe or F14???!! I've still got some plastics for one of those too!