Original poster: "bob by way of Terry Fritz <twftesla-at-qwest-dot-net>" <yubba-at-clara-dot-net> hi terry, this oltc stuff reminds me of the early days of mmc's. i cant wait to see what happens when you build the secondary and see what happens to the sparks, if any. Maybe even flames like from a vttc even. I cant seem to find any reference to the igbt's you are using?? keep up the good work. bob golding