Re: Recent s.s.t.c work

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "K. C. Herrick" <kchdlh@xxxxxxx>

One might be tempted to a little schadenfreude when viewing

http://hot-streamer.com/temp/KCH_debug.jpg

my work-in-progress photo. But after a few design and wiring 
error-and-omission corrections, the main board (at the right) is 
chugging along beautifully, much to my satisfaction--and exceeding 
expectation by a whole lot.  Currently, I'm about to make a small 
logic-improvement on the controller-board at the left.  Also, upon 
connecting the IGBT gates I found that a) I needed more than the +12V 
I'd provided from the l.v. supply and b) for larger spark-gate 
durations, my driver supply-capacitors are not big enough (and right 
you were on that, Steve Ward!).  Happily, I could series-connect the 
12V and 5V power-supply outputs, and diminish by 2 volts the negative 
gate-rails in the drivers, thus adding sufficiently to the + gate 
excursions; with the larger capacitors they should now be n.l.t. 23V 
or so for up to the largest practicable spark duration.  I expect to 
procure/install larger cap's tomorrow & then actually apply a little 
HV (as soon as I can summon up the courage to do that).

My "pilot oscillator" scheme, for charging the IGBT-drivers' 
supply-capacitors thru the 1:2:2:2:2 drive transformer, works very 
nicely.  I find that it has the added advantage of providing an 
always-available drive signal which has been highly useful for 
trouble-shooting, as it will also be when I get to running the whole 
thing at low HV where there will be insufficient 
primary-current-derived feedback to otherwise sustain oscillation.

Ken Herrick