NEON AND SHUNTS? HELP PLEASE!!
From: Zuma [SMTP:mwise-at-ns.sosis-dot-com]
Sent: Saturday, January 31, 1998 12:38 AM
To: Tesla List
Subject: Re: NEON AND SHUNTS? HELP PLEASE!!
Tesla List wrote:
> From: Bert Hickman [SMTP:bert.hickman-at-aquila-dot-com]
> Sent: Thursday, January 29, 1998 8:34 AM
> To: Tesla List
> Subject: Re: NEON AND SHUNTS?
> Tesla List wrote:
> > ----------
> > From: Zuma [SMTP:mwise-at-ns.sosis-dot-com]
> > Sent: Wednesday, January 28, 1998 8:40 PM
> > To: tesla-at-pupman-dot-com
> > Subject: NEON AND SHUNTS?
> > I posted an e-mail a while back on my 12kv-at-60ma neon that I unpotted and
> > modified. I stepped up the insulation around the primary and both of the
> > secondaries. I also removed some shunts. The tranny had 4 sets of 23
> > shunts, I removed 2 shunts from each set. That leaving 4 sets of 21
> > shunts. In my post I stated that when I run the tranny the primary
> > heats up. It gets hot but not so hot it burns when you touch it.
> > I am wondering if anyone might have an idea if this is going to be ok
> > and would also like to know what kind of current this thing might be
> > giving off now? I was told that it is probably just heating from the
> > extra current it pushing out, which makes sense because I noticed that
> > after a while the power cord began to heat up. I don't think it is
> > shorting at the primary because I had a problem once with a 15kv-at-30ma
> > neon that smoked within a minute because it was shorted.
> > ADVICE IS NEEDED, PLEASE
> > Chris
> Removing shunts allows more primary magnetic flux to engauge the
> secondary, increasing the secondary's short circuit current. Since
> there's no free lunch (on Chip's List as least :^)), this also increases
> the amount of primary current drawn. A shorted primary would most likely
> cause severe overheating or your line circuit breaker to pop.
> If you want to measure your tranny's new short circuit current,
> CAREFULLY connect a 100 ohm 1 watt resistor directly across your
> transformer's output bushings and measure the output voltage developed
> across the resistor with a cheap battery-powered VOM or DVM. Hook
> everything up solidly, and ramp the power up with a variac... and STAY
> AWAY from all of the HV side wiring and the meter while making the
> measurement. Look for any signs of arcing while ramping up the voltage,
> and fix the problem. Set the variac to output 120 VAC.
> The low valued resistor will force the transformer to go current
> limiting mode, and the AC RMS voltage you measure will allow you to
> measure the value. Let's assume you measure 8.5 volts:
> Ineon = V/R = 8.5/100 = 85 mA
> This approach also comes in very handy when you get "warranty return"
> transformers, since these often have missing faceplates - the faceplates
> are often removed and sent back to the neon sign equipment distributor
> for credit, saving the hassle of sending back a big pile of 40 pound
> Hope this helps, and safe coilin' to you, Chris!
> -- Bert --
I have a question concerning this. I tried this and according to the
meter it was reading a max of 6.0 volts. Does that seem right? I used
the same size of resistor you suggested to come up with this 6.0v.
I also wanted to ask if not running full 120volts through the primary
affect the ma on the secondaries? The plug I used is running at has
a fluxuating voltage of 113-115volts according to the meter. Could this
be why I am not even getting more than 60ma out of my tranny? Remember
I removed 2 shunts from each of the sets of 23, so my line of thinking
says I should have increased the ma at least a little. But no such luck.
do you think removing more would help or would that possibly destroy
my primary or even the whole transformer?