Well very disappointed, same thing as the other chips, I monitored DC voltage to 30 volts and was ok. Turned variac up to 90% and bang..chips went again and blew fuse. I verified before firing it up yesterday the Kerathium wafers were isolating the back of the chip from the chassis. The hold down clips were not touching anything. So therefore I cannot believe there are 4 bad chips. I think there might of been a flaw on the board causing this. I did verify I was getting continuity to the B+, B- pins.I have attached some pix of the entire build.