The tacho seems to be about 50 to a max of 100 rpm out compared to the vfd, but to be honest its an $30aud ebay tacho so I don't know how accurate it is, the vfd may be right or the tacho may be right. I don't think 50 or so rpm isn't going to make much difference, well I hope not anyway. Hoping to test today on some wood.
I did check the earth on the spindle, I had seen this while researching wiring up the vfd, looking at the pin schematic of the spindle I had to laugh because pin 4 was earth but... wait a minute theres not even a wire on the internal pin LOL! So I had to wire it up to the body and learnt how to check for continuity with that new skill checked wiring after cable was soldered and all was good. Should be able to get it running today and will report back.
I am now curious as to whether or not I should get it wired to the gecko 540 or leave it as is, any recommendations on that, is it worth it or not?