After many hours going over this board with the DMM checking continuity, i have finally found the problem, as i originally thought, it was a broken trace where the previous repairer had changed a chip and put in a socket.
There were 4 re socketed chips all up.

I went through the schematics with both sound boards, and compared the findings with the working board.

Hooray  i have repaired the trace and the board works 100% 

thanks too those who offered help with this problem

Ian