Hi Beshires,

Yes with the cap discharge into the tube. I have dumped up to 1000v into it. Wall AC into microwave transformer, HV output through bridge for HV DC. That HV DC charges cap bank and the positive of that cap bank is attached to the HV rod in the tube. The circuit is connected with a copper switch on the negative side between the low voltage source negative and the hv cap bank negative. When that switch is connected, hv cap bank jumps gap into the diode towards lv source and back to hv cap ground.

If the grid is connected to coil and coil goes back to ground - by one of several possible way (direct to hv neg, on neg of lv source, etc...) then as soon as switch is connected the hv potential quickly causes diode to slam shut then take the route to the grids, through inductor back to ground.

IF that hv source actually has some charge like the booster cap in the water sparkplug circuit, then that LV source [may] discharge over the grid through inductor and back to ground giving a super enhanced effect. It is possible Gray's battery on the low voltage side followed the HV but again, I have had the bare basic small effect of pulsing the coil and repelling a magnet (coil that had a core on it - magnet is regular rectangle ceramic magnet) - and there was nothing in the lv side...just an empty polarized cap.

With ignition coil discharge into the tube it is just like in the video.