Neon Transformer Secondary resistance

            Neon Transformer Secondary resistance
            Thu, 10 Apr 1997 18:05:29 +1000
            Phil Chalk <philoc-at-ozemail-dot-com.au>

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 !


Phil Chalk.