Power supply to the SYS1 board is 35v, driver is a DRV50 set at 4A, Sonceboz 6600R174 motor 4.7A, at the motor end connection I checked the two pairs of two wires one pair make G & GW the second pair make R & RW, with no load 360 + & 360 - works well, under load (cutting) -360 loses steps, first pair of wires read 3.9 to 4 volts, second pair read 5.8 to 6 volts same readings whether clock wise or anti clock.
Have tried the motor on a different axis output and works as it should no problem, the problem has to be in the driver board, been in touch with Roy @ DIYCNC sending it back for him to check out and repair.
What i would like to find out is what voltage readings should I be seeing on the two pairs of wires should they be the same? should one pair be different? I know one is Step the other is Dir but that is as far as my electrical knowhow goes.

Thanks
Phill