Okay... Seems its my system 3 board so I need a new breakout board and a pair of 2.5amp drivers... Anyone out there got these lying around? Have 2 SY60STH88-3008BF 3Nm nema 23 motors to trade, had about 100 hours of use each..?

Will post these on the classified section of the forum along with various spare bits I have if no-one comes forward...

Good to get to the source of the problem at last, I suppose having rechecked everything 3 times at least I can be pretty confident its all sound (except the board of course)...

Steve...