What am I missing?!?!?

[Conrad73]

What am I missing?!?!?
 My coil worked fine when driven with my 12kV 60mA nst. I killed one of the nst secondary windings, so I tried driving with a large flyback, both ac and half rectified, nothing. I know that the zvs and all flybacks I tried are working, I get good arcs between the secondary side. I've tried tank cap values from 10nf up to 50nf, as well as tapping the primary everywhere from 5uH to 60uH. I'm a bit frustrated, I think that I'm making some stupid fundamental mistake here. Any advice is greatly appreciated.
 The coil itself has a 13 turn flat primary of .25 inch copper tubing, and a 4.5x20 inch secondary about 1150 turns of 26ga. wire.
 High voltage transformer is a UY30 core of PC40 ferrite mix.
5 turns on the primary, 12ga. 750 turns secondary, 28ga.
 2500w zvs driver 24-60v.
Tank caps are dtr 6kV .440uF in series for 5-100nf

[davekni]

both ac and half rectified, nothing.

AC will not work.  Frequency is too high to charge MMC.

If DC isn't working, your transformer isn't generating enough voltage to trigger spark gap.

[55#sofcopper]

How much voltage are you inputting to the ZVS. I once ran a coil about that size from a flyback from a crt. Input voltage was around 48 volts. And 100 nf is kinda high capacitance for such a power supply I'm thinking.

[Conrad73]

I haven't put more than 50vdc into the zvs. So I'm guessing my unrectified output is 6-7.5kV. I haven't found alot of material related to inductive dc resonant charging. I'm waiting on some hv hf diodes, hoping that they will be pretty close in voltage drop, coming from the same batch, to rectify and a pair of mot's to use as an inductor to decouple the hvdc from the tank.