I am facing a new problem tuning a set of 4 320 gecko drives. I am using the following system:

Software:  Mach3
computer:  Dell c640 2.o GHZ INTEL PROCESSOR
           1 mbyte ram
Interface; SoundLogic Combo Board, from Campbell Design

Servo:
  Power Supply: 65 VDC 10Amp
  x & y servos: 875 InOz
  z servo       1125 In0z

My problem is that regardless of the settings of the three pots, I get faulting.  I have reduced the speed, to 50 IPM and 15 sec acceleration. The Step and direction pulses are set at 5. 

I set up mach3 with a kernal speed of 25KHz.  I can function the jog but it will fault out every time.

Any help will be appreciated.  We scoped GECKO output and cannot get the dampening correct. The motors seem to be tuned correctly, they will hum when you attempt to over-power the servo.

What kind of encoders are you running?
You could be getting noise over the encoder lines or losing pulse count somehow. Remember to ground the encoder shield wire only at the drive end.

I am running USDIGITAL E Series encodes with 1000 count wheels.  I have just ordered differential transmittes and receivers to aliviate the potential noise problems.

All signals are run in shielded cable which is grounded at the gecko driver.

1000 COUNT encoders on a G3x0 drive!   Probably there lies your problem.   the Gecko's error trip is fixed at +/- 128 encoder counts, so at 4000 counts per rev of your encoder the drive will trip at +/- 11.52 deg of following error which is not a lot.

It could be that you could tune the gains to work but then you hit either current limits (limits Accel) or voltage (max velocity) which would be power supply rated.

I have used the G3x0 drives successfully with 500 line encoders with small motors with sufficient reserve power in the supply, I could not make them work AT ALL on my Hardinge with 300w motors and 2500 line encoders.  I went to cncteknix tek10 drives for that, and even they were fiddly to tune and I had to use 1024 count error trip.

Wayne.... 

Perhaps try increasing the pulse length in Mach.

Your encoders are too high count you need to use under 500 line.  On one setup I use 100 line encoders and can get 1000 IPM with a 90V motor at 80V's.