I've seen a few times that adding "resonant capacitor" in parallel with the primary coil will result in improved performance. Now I don't know what is meaned by "improved", be it more efficient or higher voltage etc. I don't understand the physics of it but I ran a test anyway.

Nothing of practical interest was obtained, I plugged the inductance and frequency into an online tank circuit calculator 16kHz, 100uH = 1uF capacitor. Well, it definitely had an effect just nothing useful.

The transformer was just a 1:1 ratio on a small ferrite core. Driver was a 12V variable duty 16kHz square wave.

12V 16kHz 5% duty turned into low voltage low current sine wave. Interesting but with a 0.08A short circuit not good for much.

12V 16kHz 80% duty gave a drop in voltage and very high current draw, it killed 2 caps before I could photograph it. FETs and caps got very hot quick.

Is there any actual purpose to adding a capacitor to the primary input?

It seems too good to good to be true, literally every CRT TV transformer listed for cheap.

https://www.iccfl.com/index.php?cPath=137&osCsid=7kocq2ep9uefospi29r8n9m4o4

I'm almost convinced to try order one just to see if it turns up.

I've been looking at using one of the analogue HV meters found on Aliexpress/Ebay which are essentially a milliamp meter wired through a high value resistor. So in theory to convert a 100ma meter to 100kV meter you just need to add a 1GOhm resistor in series, same resistor is true for 10ma to 10kV etc. directly convert ma to kV using 1G of resistance.

This should hold true for the digital meters too correct? so this https://www.ebay.com.au/itm/181340921927 200ma digital meter in series with a 1G resistor should read 0-200kV, will this be at all accurate at the low end? if I wanted to differentiate 3kV and 5kV for example.

I'm asking this as I did buy a 50kV meter a while ago, and now that I have a HV probe I can test it. It only reads half the true value.

I'm curious about the P5104 HV/HF oscilloscope probes https://www.alibaba.com/product-detail/20MHz-P5104-1000X-40KV-High-Voltage_1313156951.html It looks like the only HV/HF probe that's even moderately affordable.

I've never used anything but standard passive probes that come with cheap oscilloscopes. Is there anything to know about using probes like that above? is it as simple as set to 1000x and plug and play? Will it function on any 1000x scope?

I'm just after some anecdotal accounts of how long capacitor banks take to charge, no calculations. Try to give capacitor voltage and capacitance, and charger voltage and current if possible. And a description of the charger type.

I'm planning on constructing a spark gap to measure voltages amongst other things, for the electrode rod that will be threaded to fit the actual terminal electrode (be it needle or ball etc.) it can be either brass or copper, the price is much the same surprisingly but the difference being brass being more robust and copper more conductive. I'm not referring to that which the actual spark jumps off, rather just the connecting rod.

Will the conductivity difference be totally negligible in every practical sense?

It will be a sliding contact between electrode rod and fixture, I'm not sure is the oxide layer will be better or worse between copper and brass. Probably another insignificant thing I'm considering.

It will be 8mm rod over 250mm, and at most 50kV and perhaps 50mA at a round'a'bout figure.