Help with a 500w Spindle Controller

I'm in need of some help, I've purchased a 500w spindle controller from aliexpress.

I just need to know the correct polarity for it, I live in the UK so its 220v.

The one I have purchased is in the pic below, the glass fuse inside matches with polarity shown in the pic also.

But reading the DC voltage output for the spindle I'm getting a OL on my meter when I'm meter it set to 600vDC (The controller is 0-100vDC)

Looking online at loads of videos and pics they seem to have the polarity the other way round. I scared to do this just in case I cause damage.

Can anybody confirm please

Thanks
Paul
https://www.cnczone.com/forums/attac...d=452130&stc=1