Fine tuning

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Steve Zeitler" <zeitler-at-verizon-dot-net> 

OK
the coil at the museum in Philly is back up. It turns out that the rotary 
gap setup was beginning to fall apart. Parts had shifted out of alignment. 
After 8years of daily use, it's not bad. I have been given permission. to 
soup the coil up a bit while it's in the shop.
Right now I'm using 2   70:1 potential transformers to replace the old 
homemade ones. They allow me to run the  rotary gap at a much higher speed 
and get better streamers.
My question concerns ballasting.  Now each pot xfmr.has 4ohms of heating 
elements in series to limit the current to 10 amps apiece. This loses 40 
volts and dissipates 400w, 800 total. so 1/3 of the 2500w input power is 
lost and my input V is 11-12kv rather than 16.8kv. Can I use something not 
so lossy? I've heard of inductive + resisistive ballasting but I need more 
detailed information.
Copper tubing is on order to replace the existing insulated wire primary so 
I can find the right tap point for frequency tuning as mentioned before.
                                                        Steve Z
                                                         Philly