Quote Originally Posted by andy_con View Post
bit of a thread hijack sorry.

so when I got the machine it turned on and worked, but every time I started the spindle it tripped the RCD. I notice straight away the main fuse on the sprint drive card had been bridged, so assuming it was a known problem.

after many hours of faffing I took the top cover off the sem motor and it was filled with burnt carbon from the brushes. after a really really good clean and hoover, it worked and didn't trip the rcd.

I also replaced the brushes in the side of the sem motor just for piece of mind.

a problem since I had the machine is you start the spindle at say 3000rpm and it starts to jump around going up and down, by like 300-400rpm. so sent it away for a £500 refurb and it hasn't fixed the problem just changed the problem. now days when I set the motor to 3200rpm, it will go to that speed then after about 10 seconds jumps to 3800 where it will just sit until turned off. its not a big deal I have live spindle feed back so I can account for it, but it shouldn't be doing it.
I had similar issues. Brushes need to be clean and carbon free (And clearly not worn out). I stripped the motor down as far as I could and found that previously someone had put some putty on the wingdings. I Can only assume the motor had basically started to fail and this was a 'plaster' to keep it going.

I would only get around 30% of full current before the motor would stall. It would then overheat and start smoking from the brush area.

I triple checked the setup and verified with the supplier of the drive (they were really good) - KEITH SANSBY <[email protected]> . So clearly the motor was the problem. Symptoms also included 'hunting' around high speed and any loading would make it worse.