Sprint/micromill/BOB problem

[robertjenkins]

I am replacing all the Baldor board electronics in my Micromill 2000, having fried the original board. I am pretty sure the Sprint spindle driver is OK so I don't want to replace it, but I am having some difficulty with it. I'm not sure of the version and can't find a manual but it's the same as this one

I am using a generic Chinese BOB to send it 0-10V (which is working), but the DC output from the Sprint to the spindle never gets above about 25V which means the spindle turns slowly. I'm wondering whether it's a grounding issue. The BOB is getting its 5V DC from an isolated PSU and its 24V from another PSU; these two don't share a ground. And I don't think they share a ground with the spindle -ve terminal. But I could be barking up the wrong tree here

[TDIPower]

so you see the 0-10v change on the output from the bob but the sprint isn't responding to the level change?
Have you put a pot on the 3 terminals for speed control on the sprint and tried it that way? 0v wiper 10v
If both of those check out then it might be something to do with some issue I have read about the sprint 0v being at mains level or something odd like that. so you can't connect the 0v from the bob to the 0v on the sprint (i'm not 100% as I've not done this myself just what i have read in the past)

I posted up a sprint manual in the starturn section, it might be the same. viewtopic.php?f=46&t=4778

Pete