Gecko G540 Red Led Issue

Hi All

I am in the process of rewiring a controller for Denford Easimill.
The machine came with a non-working controller that used a GECKO G540 to drive the existing Denford stepper motors.
I have been rewiring and checking the status with the led's on the G540 and up till now has been fine(Green).
I have just tried to plug in the axis and as soon as I plug in more than 1 the led turns red, it doesn't matter which axis I use. If I limit it to 1 it is fine.
The power supply I am using is 60v 10 amp but I have wound it down to 50v.
The G540 is not connected to the parallel port and I have disconnected limit/home switches etc.
Can anyone help? Electronics is not really my strong point so please give me simple answers if possible.

Many thanks.
Greg