SO I messaged Gary and we talked over the issues, I noted that there was a brake on the stepper with 24v supply that might cause issue - she he said get rid of it and try again.

Removed the brake, ran the standard ZPA profile for mach and the stepper motor jittered so violently that it nearly jumped off the desk!! Not the 24v supply I am guessing. . . . .

I'm totally confused now so heres the rundown of trials to date -

It has worked with the pro tune and with the direct parallel connection ( I wired up a parallel to stepper driver cable and it worked a treat) so there can't be any issue from the stepper-drivers to the steppers, or in fact the computer outputting signals.

It has not worked in and out of the case, I initially tried it out of the case and thought the problem was as a result of it not being grounded properly. It did exactly the same when I put it in the case - so it can't be something isolated to its assembly and orientation in the case.

. . . . . So, I am going to put the Zpa unit in my other machine to see if somehow I have lunched it. I bloody hope I haven't because it was doing the same thing with both the ZPA boards I have - so I would have knackered both!!

Whatever is going on is happening on the ZPA board. I will wire up the board to my other machine tonight (GEKKO 203V's - worked a treat with them) but if it doesn't work I am seriously considering getting another board to try. Annoying though - £20 for the ZPA is a good price for a punt, but any more serious board will require more dollar. ... . . . and it still might not work!!!

Anyone got any suggestions for a cheap driver board that will do the job?

Chris