Re: Neon Transformer Secondary resistance

            Re: Neon Transformer Secondary resistance
            Sat, 12 Apr 1997 01:38:00 -0700
            Bert Hickman <bert.hickman-at-aquila-dot-com>
            Stoneridge Engineering
            Tesla List <tesla-at-pupman-dot-com>

Tesla List wrote:
> Subject:
>             Neon Transformer Secondary resistance
>        Date:
>             Thu, 10 Apr 1997 18:05:29 +1000
>        From:
>             Phil Chalk <philoc-at-ozemail-dot-com.au>
> Organization:
>             Secure_Logic
>          To:
>             tesla-at-pupman-dot-com
> G'day all,
> Greetings from sunny Sydney, Oz. I am a 36yo Electronic Engineer, just
> recently unemployed.  So now I finally have a bit of time......
> I've been watching this list now for some months, & have learnt heaps
> from all of you - many thanx.  Unfortunately time restrictions etc, have
> not allowed me to digest all of it, let alone catalogue it, so my
> apologies, as I believe this has already been well covered.
> Well, today I scored myself, for free, a 12kV 30mA potted transformer
> from the local neon shop.  As someone else recently described, I was
> suitably shabbily attired in 'work clothes', looking dirty, and oozing
> poverty.  I greeted the smiling office boy with "G'day mate, I'm on the
> scrounge...." and asked if they had any old junked Txfmrs.  No-one
> seemed to know what a Tesla coil was, but I was eventually handed 'the
> beast' with a cheery "Dunno if she goes, mate." Who cares ! 'She' was
> free !
> In case any of you are familiar with it, it appears to be S.E.M. r.s.m.
> brand (It appears to be of Italian manufacture), dated 10th '88.  240v
> primary (just how we like 'em, here) -at- 1.46A.  The Secondary says
> 6000-0-6000V 30mA, 300VA.  I presume the centre-tap of the secondary is
> connected to the metal case, which has earth screws fitted inside & out.
> I made some measurements before I flashed it up, and though it generates
> a nice fat healthy-looking 12kV spark, the secondary resistance readings
> bother me a bit.  Across the secondary measures about 20.2k, however
> measuring from the case shows about 11.9k to one end & 8.3k to the
> other. The centre-tap's not so centre !
> So, please, is there another explanation - are there internal ballast
> resistors to ground, or something.  Is this anything to worry about ?  I
> don't have the technology, at the moment, to measure 12kV ac, but will
> do so shortly, out of curiosity at least.
> I'm itching to build my first coil, and will use this Txfmr anyway -
> this is what I've been waiting for to get started - but would welcome
> comments from anyone experienced with these things.
> Many thanx, in anticipation.  And I'll NEVER write one this long again !
> Regards,
> Phil Chalk.


The secondary coils should be matched, and 9k Ohms to the centertap
should be in the right ballpark for a 12 KV 30 MA trannie. I'd use it as
it stands, and if it "blows"... well you can always get your money back
for it! :^)

Safe coilin' to you, Phil!

-- Bert --