Rotary phase adjustment

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

Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>" <Esondrmn-at-aol-dot-com>

I was working with my 3.0" coil the other night and noticed there are two 
points of adjustment on the phase angle control variac where the coil runs 
smoothly.  I find these points by turning up the power to about 30% and then 
adjusting the phase control to where the safety gaps quit firing.  The gaps 
are brass cabinet knobs and if I remember correctly, are set to somewhere 
between .35" and .40".  One position is clearly 240 bps and I can get to full 
power here with the safety gaps not firing if adjusted just right.  The coil 
runs well, smooth and with a constant tone.  The other position seems to be 
firing at 120 bps.  I can tell by watching the gap (my control position is 
only about 8 feet away), it is uncovered and you can see that it is locked in 
at a different place.  The performance of the coil is also much different.  I 
have two toroids on this coil, just like on my 6.0" coil.  The first toroid 
is mounted just about two inches above the top of the secondary then a larger 
toroid is mounted on a hollow aluminum spacer up about 6.0" above that.  When 
firing at 120 bps, there is a very intense corona coming downward from the 
lower toroid with discharges to the strike rail.  This is happening at about 
60% of full power.  I cannot increase the power above this level at 120 bps 
as the safety gaps will not quit firing.  It is obvious that the tank voltage 
is much higher in this mode and the secondary spark activity is much more 
intense.  I would like to open up the gaps and give it a full run in this 
mode - but when I was first testing this gap a few months ago, I tried 
running it at 120 bps and burned up the secondary.  I really don't want to do 
that again.

When I get this set up on my 6.0" coil, running at 7 kva, the rotary gap will 
be located in the cabinet below the coil and I will not be able to see it 
fire.  I definitely want to start out running it at 240 bps.  I guess I can 
determine whether I am at 240 or 120 bps by finding the spot where the safety 
gaps can be set the closest and still run at a given power level without 
firing.  The lowest setting would indicate the correct 240 bps rate.  It is 
nice that John's control circuit provides the option of running at either 
rate - but mandates that you know how you have it set up.

Ed Sonderman