Strange cut motor sound

Running a quick 5 min centerline carve, suddenly noticed the sound changed. Found machine running stopped in one place slightly above the board running at varying speeds. Slow and slower, no movement in any direction, approx 2/3 thru mpc. Would not stop with stop button, turned it off. Thought maybe the varying speed indicated a brush problem so I changed them. Found they were approx 1/2 length. Started same carve over again and all seemed well. Heard the machine slow down and run at a steady speed but not fast or under load. Found carve finished, truck homed but still running at low speed. Would not shut off with stop button. Used on/off switch to stop.
Removed board and did a second carve of the same mpc. Machine seemed ok, thought it sounded off but assumed it was just me being paranoid. Carve finished, went to remove the board and as I was cranking up the machine started running the cutter. Found that as I cranked up the cut motor would start in small spurts. Nothing when I cranked down.
Anybody have any ideas which wire could be pinched somewhere. Something has to be turning it on and I'm not familiar with the wiring/cabling to make an intelligent guess.
Appreciate any help,
Rick H

I see you joined in 2007. This was a common problem in 2008 with the "A" Series machines. A Vibrating QC would cause the C1 Capacitor on the X Termination Board to snap one leg. The leads would touch then not touch and this would cause the Q1 or Electronic Switch for the Cut Motor to start and stop without the CW Computer wanting it to run.

OR static electricity from your dust collector caused an arc on the X Termination Board burning some components.

This is a very good reason to not bypass the cover safety switch. When changing a bit it could get interesting....

Al,
You hit on the head. Capacitor C1 lead broken. It's a B machine but still had same problem. I had a spare board so back up and running. I agree, scared the hell out of me when I started to crank the machine up and the cutter started. Any chance you know the value of C1. I can't tell from the labeling. Have a variety from old radio/tv days.
Thanks a bunch. Didn't remember that problem, the one on the power supply comes to mind.
Rick H

I will check in the shop tomorrow. I bought a bag of them. They have a higher voltage rating but that does not matter. So they have a thicker lead.