Fine Jimpinder,
Well I have a card named breakoutbord  C1 from cnc4pc.  It is optoisolated yes.  Okey I now the eletronics behind the card -the VFD is from -80 
and possible not so fast  as a new one. But in this case this part was out of work becaurse the spindel is not moving.  
I have a brand new pc to drive Mach but I have this step fault even before I change the pc.
It was great if any other person how have the same card and is in same situation can verify this extra step.
I have just order a new card like C11 from cnc4pc but have not made any test yet.  I´m not very well on electronics, I most take the time to do 
all right becaurse I have only one chance  

Intressting to here about slow timing between the circuit.  In config/port and pins and about the Kernel speed.  Have this any thing to do with 
with the speed between the circuit. I think I drive the new pc at 60khz.   Ok, before I will start to change the card I like to read if any other have 
same experience.