Unfortunately one of the issues of having purchased a 2nd hand machine that you haven't seen working and has been modified is not knowing why the modifications were done. At this point I'm trying to work out the wiring of the spindle to the VFD. The VFD is a HY01D523B and the spindle is a GDZ-65-800. The spindle has a 4 pin connector on it but the cable from the VFD looks to have been modified with only 3 wires coming out of it and wrapped around a ferrite choke. I'm not sure if that's all this spindle needs to run, but having never used these spindles and VFDs before I don't want to experiment by plugging it in as is without checking over everything first. I've got the checklist of settings for the VFD from another post so the wiring is all that is holding me up from powering it up.