Original poster: "D.C. Cox by way of Terry Fritz <twftesla-at-qwest-dot-net>" <resonance-at-jvlnet-dot-com> With peak currents of over 500 Amperes you need a much better ground for your sec. At least 4 AWG fine stranded welding cable. The heat in the 12 AWG is indicating a lot of loss. Dr. Resonance