Re: "> I have acquired a ART-13 via a trade. I am seeking sources of > information on modification, operation, etc. i.e. how can I run the > auto-tune." All it takes is 24-28 vdc for heaters and autotune. It doesn't need any 400 cycles. The ART-13 doesn't need any modification, just some capacitance on the output connection for proper loading. Richard Brunner, AA1P