[Al Skierkiewicz]

Den,
This is one of those situations where you need to weigh the benefits against the hazards. For a few minutes of frustration you save the $1000+ price tag of a new controller. Seems like a no-brainer to me. There should not be any direct connection between the frame and the electronics but the welding process passes huge amounts of current through the frame. Current passing through a conductor induces a magnetic field (Huge currents=huge fields) and conductors in a magnetic field induce current flow.