Right ive replaced the Pot and we have had some success the sound works for a while then cuts out reboot the machine and the sound comes back on for a little while then cuts out again.  When the test button is pressed it plays the constant tone but doesnt cut out   

  Where should i look now ive replaced all the caps on the board and it also has new CPU \ Rom \Pia \Crystal

 Cant wait to finish this one so i can get it out of my shed