Original poster: "Jim Mitchell" <Wrenchead-at-starband-dot-net> I got some large 600v triacs, and would like to try to make an sstc vttc hybrid by driving the grid of a large power tube with a variable frequency from a TL494 or a 555 timer. Any idea how I should wire this up, As the grid needs around 400v to interupt the flow, instead of a grid coil, this would be used, any suggestions?