Hi John,

So I checked all that and all seems t check out ok so pretty confident it's isolated.

I have a attached an image of the terminals on the motor controller.

The board I have is a cheap USB board

https://buildyourcnc.com/item/electr...ach3-USB-Board

I'm not at all sure of how the board will connect to the spindle controller. In the description of the spindle controller it states:

7. the given signal mode (V / mA): the default potentiometer, 0-5V, 0-10V, 4-20mA, PWM, button type


Click image for larger version. 

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Be very grateful for any ideas!

Cheers