Novamill - Mach3

[m_c]

Are you using the original Sprint speed controller? If so do NOT try connecting the BoB 0-10v output to it as the controller is isolated from ground and its 0v floats at something round half mains voltage. An isolation circuit is needed. I've got a Novamill with a slightly different Bob but happy to share xml when I'm back home. Also can possibly help on the isolation.

The machine has been running, so I'm guessing there must already be some form of isolation.
Going by the photos, I'm guessing P17 is being used to control the SGR (Spindle Go Relay aka switches on power to the Sprint drive), and then the little red wire next to it from the P1-PWM terminal is being used to control the speed.

However to use that, I'm guessing there is another PCB mounted somewhere, because as far as I can remember, the Sprint drive only accepts a 0-10V supply, which must be isolated. Unless it happens to have an isolated Sprint drive, but AFAIK Denford didn't use isolated drives.


Just to be clear what we mean, due to the design, SCR motor controllers (which the Sprint is), the speed control voltage sits at roughly half mains voltage, which is why it needs to be treated with caution. You do risk giving yourself a tingle if you touch those pins/wiring with it powered, but the equipment risk is by connecting them to a non-isolated circuit, magic smoke will be released.

Can we get a full photo of the Sprint drive (lower right corner of your photo)?
And where does that little red wire go to?