Re: safety gaps

To: tesla-at-pupman-dot-com
Subject: Re: safety gaps
From: Richard Hull <hullr-at-whitlock-dot-com>
Date: Mon, 24 Jun 1996 09:36:44 -0700
Tesla List wrote:
> 
> >From tweagan-at-maind.dnet.dupont-dot-comSat Jun 22 07:55:50 1996
> Date: Fri, 21 Jun 96 15:01:41 EDT
> From: tweagan-at-maind.dnet.dupont-dot-com
> To: tesla-at-pupman-dot-com
> Subject: safety gaps
> 
> > Also, he explained why the "recommended" circuit doesn't need additional
> > "safety gaps" (or capacitors from neon transformer to ground), and described
> > suitable torroid and air-core chokes for the "recommended" circuit.
> >
> > MY QUESTIONS:
> >
> > 1.  Do you agree that the "recommended" circuit (fig. D) is better than the
> > "conventional" circuit (fig. A)?
> 
> > 3.  Do you agree that additional "safety gaps" (and "capacitors to
> > ground") are not needed in the "recommended" circuit?
> 
> <Now to your Questions, in order.
> 
> <1.  In general, yes I believe shunting gaps are better but not the
> <panacea Mr. Cox believes them to be.  When the gaps stop firing, there is
> <still a load of expanded magnetic energy in the primary tank this will
> <kick back into the transformer.
> 
> <3.  I have long ago cast the safety gaps aside.  They often do as much
> <harm as good and besides, in the shunted gap mode, the main gap is also
> <the safety gaps.  I still shunt each xfrmer lead to ground with 500pf!
> 
> <Richard Hull, TCBOR
> 
> Richard
> 
> Could you go into a little more detail why you no longer use safety gaps-
> how do they do as much harm as good?
> 
> Is it because you use more rugged potential and pole types or do you
> disregard the safeties with neons too?
> 
> I understand the use of 500pf caps to ground, do you rely on these to
> shunt nasties away from the transformer?
> 
> Thanks
> 
> Tom


Tom,

I have used the shunted type of gap that Cox recommends for years, so, 
once again safety gaps would be useless!  Pole and Potential 
transforemers are more robust and require little protection anyway.  I 
don't even use 500pf caps or safety gaps on neons anymore!  I use them so 
infrequently now and only on coils under 100 watts and limit the run 
times as well as have 59 spare neons in several sheds so protection is no 
longer of any real concern to me.

I haven't leaped into any of the chatter on this stuff lately due to the 
fact that after all these years,  I know to:

1.  Never run a rotary on a neon.
2.  Keep the duty cycle of operation ultra-low. 10-30 sec run times, max!
3.  Never run high power ( <500 watts ) on Neons.
4.  Expect them to fail at any moment.
5.  Never ever buy a new neon sign transformer for any reason whatsoever!
6.  Never use a neon on a magnifier. (too tighly coupled)

Richard Hull, TCBOR