John, "David, The triode config. is fine but may limit the spark length. In a test I did, I installed an 803 into the same schematic design TC that I sent you, and obtained a 5 to 6" spark, by connecting a 15k resistor from the plate supply to the screen grid, and then connecting a 45k resistor from the screen grid to the suppressor grid. It was just a quick test and I didn't measure any voltages or try different resistor values, maybe someone on the list has done more in this area? Happy and spark-blasting tube coiling, John Freau" I am a bit confused as to which is the screen and suppressor grids. Attached to this measage is a schematic of the 803, if you could kindly tell me which is which, I would be very greatfull. The 15K resister to G2(2) or G3(4), and the 45K across them? G1(3) would then go to the Grid leak coil, correct? Thanks for your help, David Trimmell