Ferrite core test (low output?)

[nielsquake]

Hey guys long time since I posted on here since I had been busy with school and unable to work on my HV projects but recently I got into it again by using some of my old ferrite cores from old TV's and wind my own secondary on a 3D printed frame. The one I made with a ferrite from a tv worked really well but I found out I had a bigger ferrite laying around from the old filament transformer for an XRay tube. I made a secondary with many more turns (I made quite a few that seemed to have failed for some reason) but it never even came close to the output on the smaller one made from the old TV flyback.  Here is a pic from the ferrite in the xray tank



As you can see it is huge, it had small plastic discs in between for the airgap. I think it was like 0.5mm thick plastic so only tiny gap.

IDK if they use other material for high current transformers but look at this comparison powering it from the same supply and driver compared to the one made with the TV flyback core.

TV one:

Xray one:

The tv one was also gapped I think but I just used a bit of tape for that, probably at around 1mm

Does anyone know why it won't work better, could it be the ferrite material or is it more likely I messed something else up. Both of em have a 3+3 centertapped primary wound in the same direction as the secondary. I dont know why the colors of the plasma ball are so different but the output in the second vid is lower for sure when drawing arcs aswell.

[nielsquake]

also its driven by cheap ebay zvs board.

[nielsquake]

I think this was the original primary for the fillament transformer
Doesn´t seem like the turn ratio for the secondary is much higher. I´d say 1/2 or 1/3 idk. Maybe this shows some info on what kind of ferrite it could be

[davekni]

There are many transformer parameters that are important, along with driver voltage and frequency and output load (plasma globe).  Could be too-high unloaded output voltage, with correspondingly high output impedance, which is loaded down too much by the globe.  Or could be the opposite or a different frequency or ...
I'd suggest measuring primary and secondary inductances of your transformers along with leakage inductance (inductance with opposite winding shorted).  Then run analog simulation (ie. LTSpice) with those parameters.  If you have access to a scope and signal generator and some capacitors, you can measure inductance manually if no LRC meter is available.