Re: NST Life Expectancy

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

Original poster: "WIZZARD . by way of Terry Fritz <teslalist-at-qwest-dot-net>" <pbobyk-at-hotmail-dot-com>

I purchased the parts from Digi key as the schematic indicates. *attachment
I'm unsure about the next statement:
The schematic was modified such that the number of MOV is 16, eight per leg.
Each MOV clamps at 1.6KV yielding a clamping voltage of 12.8K per leg.
When I increased my RQ gap to spark at > 15KV my safety gaps should have fired.
I believe I should calibrate the safety gaps again, and possibly reduce the 
number of MOT's per leg.

???

WIZZARD
Dwight, Ontario
Canada


>From: "Tesla list" <tesla-at-pupman-dot-com>
>To: tesla-at-pupman-dot-com
>Subject: Re: NST Life Expectancy
>Date: Fri, 13 Jun 2003 19:39:10 -0600
>
>Hi Wizzard,
>
>At 01:55 AM 6/13/2003 -0400, you wrote:
>>My 4" coil and had one of the NST's die.
>>I suspect my protection circuit was the cause.
>>I made a Terry filter and put it on my remaining NST.
>>I believe the second transformer has now failed.
>
>Could the protection circuit have failed and the NST is ok??  The Terry 
>filter is designed to "die first".  The MOVs will eventually go to a 
>shorted condition if the voltage is allowed to get too high thus 
>protecting the NST.  You might try (carefully!) arcing each end of the 
>bare NST to ground to be sure it is dead.
>
>>I'm new to this game but I think a transformer should last more than a 
>>couple minutes of operation.
>>What is the normal life expectancy of an NST?
>
>With the Terry filter, they should last forever.  there is always a 
>"chance" that the NST was on the way out regardless, but the filter really 
>should save it.
>
>
>>The second 15KV/30mA transformer was doing great. The coil was tuned and 
>>my new RQ gaps were opened full..
>>I could hear some internal arcing inside the NST case and could smell a 
>>burning smell.
>
>The MOVs on the filter should have gone up in smoke long before that!
>
>>I pulled the top off the transformer immediately and some smoke/steam 
>>came out as I lifted the cover.
>
>Oh!  That is not good ;-(  I assume it did not get water into it or 
>something like that.
>
>
>>I could see the tar had cracks just like the last one that failed.
>
>That is fairly common and usually not a worry.
>
>>This time there was a small hole where what looked like water had 
>>condensed around. The liquid was also condensed on the top that I lifted 
>>off. The transformer case was quite warm if you grabbed the case.
>>What is happening?
>>How can I stop this.
>
>Double check your Terry filter to be sure it is made right.  Double check 
>the safety gap setting too.  The filter should have saved the NST, but 
>maybe the NST had water in it.  Perhaps if the NST were to dry out it 
>would work again, but that is a long shot.
>
>Cheers,
>
>         Terry
>
>
>>A quickly going broke coiler... LOL!


http://hot-streamer-dot-com/temp/NSTFilt.jpg