Re: SRSG and Terry filter overheating

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: Terry Fritz <teslalist-at-twfpowerelectronics-dot-com>

Hi Rob,

At 11:20 PM 9/22/2003 -0500, you wrote:
>Thanks Terry,
>I'm running a 15k 60ma (supposedly 70-75ma w/ some shunts removed) NST with
>a .011 MMC. Could you clarify what you mean when you say "the coil could be
>trying to go over voltage?" I will check my wiring thoroughly
>tomorrow.Thanks for answering my newbie (kind of ) questions.
>Rob

Your capacitor is a "resonate size".  This means that the voltage will grow 
and grow and grow until something blows up.  A spark gap would stop that 
"if" properly adjusted.  In the past, many coils were built this way but 
they tended to blow NSTs and caps.  Today we tend to use say a 17uF cap 
(with your NST size) that would not go over voltage if anything went wrong.

In this case, the filter did it's job and shorted everything out before the 
NST or caps were damaged just like it was meant to do ;-))  Unfortunately, 
the MOVs may have been damaged if they got real hot (melted cases).  The 
MOVs are designed to kill themselves, if necessary, trying to protect the 
NST and caps.

So what to do...  If you can change your primary cap size to around 16uF do 
it.  That is a far safer area to run at.  If not, you will have to 
carefully adjust the primary and safety gaps (which you should anyway ;-))

To adjust the gaps:

Run the NST at full power but without "anything" but the gaps 
connected.  In that case the NST will run right at it's rated 
voltage.  Adjust that safety gaps to where they just barely will "not" 
fire.  Adjust the main gap to where it does easily fire.  Then the safety 
gaps will fire if the NST voltage goes too high, and the main gap will fire 
a little below the transformer's rated voltage.


Hopefully this will get you started down the right path to fix this.  If 
not, just ask away since that is why we are all here ;-))

Cheers,

         Terry