Daniel re the sound board another check is as follows: on the CPU connector A1 J2 pin 24 is the reset line.  This should (I think, once again I dont have a Rock schematic) go to the sound board at A6 P1 - pin 9.  With the machine off do a continuity test between these two points.  Also check the wire colouring on these too confirm I am right in my thinking  I.e is it the same wire.