Re: [TCML] No-load NST's

[Sfxneon@xxxxxxx]

>> In a message dated 6/25/2008 4:26:25 P.M. Central Daylight Time,  
_Gary.Lau@xxxxxxx (mailto:Gary.Lau@xxxxxx)  writes:
 
<< Yes - I too have heard many times that running an NST with no load  will 
stress its insulation beyond what it was designed for.  But it does  seem 
unlikely that an NST should be designed to self-destruct should its  connection to 
the load fail.  So being the skeptic that I am, I have to  wonder about the 
origin of that belief.  Did it come from a source in the  sign or transformer 
industry, or just a coiler who observed that an in-use NST  with a sign operates 
at well below its faceplate voltage?
 
Gary Lau
MA, USA >>


Gary, all,
 
It's common knowledge in the neon sign trade that operating a neon  
transformer for extended periods of time with no load, such as a with a broken  tube or 
wiring, _greatly increases_ the chances of a secondary insulation  failure, 
not only inside the transformer but also in the secondary wiring  itself.
 
I have owned and operated a commercial neon sign shop and plasma art studio  
for almost 30 years, and I can say without a doubt that this is true. I'm not  
saying that _every_ NST run open circuit will fail, just that it greatly  
increases the chance the longer it runs. In fact, this just happened to a  neon 
transformer on a border tubing installation at my own shop. I failed  to 
promptly fix a bad tube, and about a week later the transformer went bad too. 
 
So, it's not likely that you are going to kill your NST if you happen  to 
hook it up without a load, unless you leave it that way for days, weeks or  
months. What really kills them in TC usage is opening up that spark gap too  wide, 
or the voltage ringing up to insane levels if the gap misfires a time or  two. 
They really, really don't like any capacitance across their output,  even 
extended GTO runs or GTO in metallic conduit. 
 
>> In a message dated 6/25/2008 7:20:42 P.M. Central Daylight  Time, 
_evp@xxxxxxxxxxxx (mailto:evp@xxxxxxxxxxx)  writes: 
 
<< I ran a "skunk zapper" electric fence for 
several years which  was powered by a 9 kV, 60 ma NST. >>
 
PS: A word of caution about using a NST for a "fence charger"! Common  
practice...but bad idea. IT'S LEATHAL, not only to small animals, but humans  too! 
Real fence chargers send out a high voltage microAmp pulse about once a  
second, which smarts like hell, but won't cause you to go into cardiac arrest or  
become unable to let go of a 'hot' fence wire. They will also not produce a hot  
enough or long enough duration spark to burn you or set the grass/weeds/house 
on  fire when they finally get that tall. 
 
However, your NST _WILL_ keep the skunks out!! :)
 
Tony Greer
Special Effects Neon
Lubbock, Texas
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