[Vintage Engr]

Thanks.
Have just looked into the link wires previously mentioned, not sure what they were for, but it's not an earthing fix, as the relevant pin numbers on IC 387/395 are inputs & outputs of gates etc.

Thanks Argus, for your info.

Have checked, and these two points are already linked, track-wise, and are at the same potential. I have tried a short wire link across the two points, just in case it might provide a better common grounding & eliminate sone of the noise, but sadly it didn't.

I will get there!