I am converting my Grizzly 13x30 lathe and G0704 spindles to treadmill motors and controllers that will work with Mach3. I fianlly got it all working and here is the scoop.

Spindle components:

p/n 314571 treadmill motor 2.8 hp 130vdc intermittent 2.6 hp 110vdc constant duty 1940 watts 18 amps.
Amt102-v encoder
DG4s Driver

My problem getting this all to work was very simple, in the programming PID with the servo configuration software there is a setting they say never to touch unless you have no choice. Well I am sure with the factory servo motors with high mass and inertia that is probably true. With the treadmill motor it is not.

Anyway when first hooked up and turned on it growled loudly. I adjusted AP to 1 its lowest setting to make the system stable, no change.
I then AD lower, and lower till I got around 100 and the growling lessened a lot. Lower setting did not help so left it at 100
Lowered the AI, as it got lower and lower the growling turned into movement, When I got round 10 it was swinging 180, I should say oscillating back and forth 180 degrees per step.

I tried everything, no effect. I asked the manufacture, Arturo at CNC4PC where I bought the electronics and he had never seen it before. I search every forum to no avail.

Then I decided to change out all the components to see if it made a difference, no it did not.

Finally I decided to change one setting that the instructions say you should leave at max if at all possible. Well the setting was the Li setting and it was 65535. I dropped it 100 at a time, no effect. So then I set it down to 10….surprise the servo finally spun, huge error in position but it spun.

I adjusted the LI up and up while the errors decreased, then used the tuning instructions that came with the DG4S and 10 minutes later I had a spindle on my lathe that worked perfectly with a very small error showing up due to the mass of the drive system and now I will also move those settings to my Mill that is using the same motor, encoder and driver.

My hat is off to Hoss, Arturo @ CNC4PC.com, Al the man (helped with powersupply design) and John_100 (also powersupply design)
IT ALL WORKS GREAT !!!!!