Another late one, so I dropped out the mainboard and the control board checked and reflowed alot of joints, nothing jumped out as dry and there is no change. I have tried turning down the Recording Gain pots RT103 and RT203 just before that sony IC and when turned all the way down there is a buzz and very high pitch noise so that is obviously what the IC is amplifying, using my phone the high pitch nouse 14khz, I'll get the scope out tomorrow to have a better look.
Re. your early point about looking at ground points what do you mean?