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Re: Neon murder

Subject:  Re: Neon murder
  Date:   Wed, 21 May 1997 07:36:36 +0000
  From:   "John H. Couture" <couturejh-at-worldnet.att-dot-net>
    To:   Tesla List <tesla-at-pupman-dot-com>


At 06:56 AM 5/20/97 +0000, you wrote:
>Subject:  Neon murder
>  Date:   Mon, 19 May 1997 23:23:20 -0400 (EDT)
>  From:   ADatesman-at-aol-dot-com
>    To:   tesla-at-pupman-dot-com
>
>
--------------------------------  Big snip



>the fuse, or I need to think about this much harder.
>   As an aside, the burned side can still generate a really small spark
>when
>grounded to the case.  Is it truly burned out, or is this maybe a case
>of the
carbon arcing I've read about (that can be fixed by baking in the
>oven)?  I
>can dream!
>    Thanks for the help.     Aaron Datesman
>
--------------------------------------------------------------

  Aaron -

  You need to think more about this problem. Most coilers do not
understand
why neon transformers fail. Most coilers also do not understand why RF
chokes in the microhenry range will protect the transformer.

  The problem is that the spark in the operating gap produces transient
voltages that can easily puncture the insulation in a neon. These
transients
are in the nanosecond range and are partially blocked by a choke of
about 30
microhenrys. Most coilers believe the chokes are for the peaks of the
operating dampened wave voltage which would require millihenry chokes
and
are not a problem. These peaks are usually less than twice the rated RMS
secondary voltage which the neon windings can handle. 

  To check a neon transformer connect a 100 ma AC ammeter across the
secondary terminals first then connect the 120 volts. This will avoid
sparks. Some coilers recommend drawing arcs with the secondary leads. I
would not recommend this practice but admit I have done it without
burning
out any windings.

  Whenever a neon is to be operated with a spark you should protect it
with
RF chokes and protective gaps regardless of the type of load. However,
it
appears that with some perfectly operating Tesla coils the harmful
transients are not large enough to cause burnouts. But this is a gamble. 

  The only time I burned out a neon was when I burned out one side of a
12KV, 60 ma neon. This was when I connected the neon to a 25 KV
voltmeter
that sparked over at the voltage reducing network. The voltmeter wasn't
damaged! I had no RF chokes or other protection because the load was
only a
voltmter. If it wasn't for the spark the neon would not have been
damaged.

  Regardless of the fuse size you use you will get 30 ma when the
secondary
is shorted provided the fuse is  large enough for the nameplate rating
(4.12
amps). However, if the windings are shorted somewhere the fuse may blow.
Your burned out side appears to be damaged beyond fixing.
 

  John Couture