Re: CD 942 failure tonight

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

Original poster: Bart Anderson <classi6-at-classictesla-dot-com> 

Thanks Terry for posting the pics (I was thinking about this today).

Easy enough to see both caps failed from the same type of event (location 
of burn). Both holes are dead-center where heat would be maximum. I can't 
see this as an event caused by some oddity such as a high voltage pulse 
(above the norm). The caps are heating up pretty quickly and I doubt it is 
coincidence. There are only a few possibilities (rf, current, or manf. 
defect?).

Take care,
Bart

Tesla list wrote:

>Original poster: Terry Fritz <teslalist-at-twfpowerelectronics-dot-com>
>
>Hi John and All,
>
>I looks at John's video and caps:
>
>http://hot-streamer-dot-com/temp/P3070026.jpg
>
>There is just a big hole in both about 3/16 inch deep.  It looks like it 
>just exploded...  There is not enough energy in a single cap to do that so 
>I don't know where all the energy came from.  There was no other arcing 
>inside.  It just looks like it got a single high energy over voltage that 
>blew a big hole in the cap.  Apparently John does not have the strings 
>cross connected or anything like that.
>
>I think he should set his safety gaps like this:
>
>http://www.pupman-dot-com/listarchives/2000/January/msg00044.html
>
>The resistors were very well attached, far from the cap, and checked out 
>fine.  So I don't see any obvious cause.
>
>There is a small chance the big 12/120 NST Transco is saturating the 
>shunts and maybe putting out too much voltage/current but I have never 
>seen that before with a LTR rotary.
>
>One thing that does worry me.  He has his primary far away from the cap, 
>NST and all.  They are hooked up with about 6 feet of wiring.  I wonder if 
>that long primary wire's inductance is doing something odd and causing 
>high voltages back on the caps or something?  I am not sure if that would 
>do something bad or not.
>
>So I don't know what is going on really :-(  but something sure is 
>strange.  He says the primary gets hot and the cap are heating some.
>I'll grind the cap through the center tomorrow and see if there is heat 
>damage.
>
>Cheers,
>
>     Terry
>
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