Re: Recent s.s.t.c. work

["Tesla list" <tesla@xxxxxxxxxx>]

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

Jimmy, Terry et al-

OK, perhaps my 30 V was not too high; in that case...I dunno what the 
problem was, yet.  As I'd reported, I'm using NPN/PNP "totem pole" 
configurations to drive the bricks.  Their collector supplies 
(charges in electrolytics) are each clamped at 30 V +/- 5% and I have 
fast diodes connected gate:+ and gate:- to clamp the + and - max. 
gate potentials to the ~30 V + the 0.7 V of the diodes.

I just now fished the busted brick out of the trash barrel and 
checked its source:drain.  Also zapped.  Does that give a hint to 
anyone?  Perhaps my phase-shifting was at the time so far off that 
turn-off occurred at peak current--although, I had the input variac 
turned down pretty low at the time.  I've never yet raised it beyond 
20% or so, of its ~140 V output.

It's the kind of thing where one hates to keep trying out bricks one 
after another to see if the problem is fixed...right?  With a 
feedback circuit dependent on primary current to operate, it's a 
little tough to do otherwise.

KCH