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RE: Geek Group Cap mod

Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>

Hi Chris,

At 01:46 AM 5/6/2002 +0000, you wrote:
>Comments interspersed.........
>>Original poster: "Dave Larkin by way of Terry Fritz <twftesla-at-qwest-dot-net>" 
>> >Hi Bert,all,
>> >I donít expect to get 80KV, heck I only have two 9KV NST's. I was just
>> >going by what the site said and using their building technique. They
>> >claim this design will be perfect for a 15/60 and they rate this cap at
>> >80kv/.0125 mfd.
>> >Would someone take a look and see if I misunderstood the internal
>> >wiring?
>>No misunderstanding on your part... The geek group are not renowned for
>>their technical competance,
>I'm sure the 200+ members, several of whom are on this list, will love that 

Nice to know you are still reading the mail :o))  I thought to myself,
Hmmmmm... I wonder if Chris is awake :o))))  I got a kick out of it ;-))

>>I suspect the 80kV rating was based on either
>>severely flawed reasoning.
>Actually, years ago when we built them we asked what the breakdown voltage 
>was and were told "Don't worry about it it's something like 80kV" so that's 
>what we wrote on the caps. When it came time to do the site, I went and read 
>the caps, and it went on the site. I've never given it much concern.
>>A more sensible DC rating for a longneck beer
>>bottle (miller, corona, becks etc.) would be 40kV or so, depending on the
>>condition of the glass and the creepage path down the neck.
>Prove it, then I'll change the site, the caps, and the manual.

I set up a little test tonight to hopefully salvage our reputation a bit ;oD

I was "thoughtfully" holding a Miller Draft long neck as I read your post.
It's a tough job, but somebody has to do it!!  I "cleaned" the bottle out
and made a quick little capacitor out of it:


I then set up the Bertan lab X-ray power supply to put it to the test:


There you go.  At the 50kV limit of the supply, the bottle held "just
fine".  I suspect most of the 67uA of leakage current was from corona of
the wiring which was "sizzling" with electricity.  

After awhile it started to get a nice blue corona band to the ground foil.
It was about 5 inches long and 1.5 inches wide and bright blue.  It was
really cool!!  Then POWWW!!!  The two terminals arced over.  It was
interesting that it did not track on the bottle but choose an air path
about 1 inch away from the bottle neck.  It seems very high voltages just
go where they want and tend to ignor the surface tracking thing.  I did not
use oil as your bucket cap does to prevent this.  If I had, the arc over in
air problem would have been eliminated.  I almost wonder if the oil is
needed for normal TC use?  But I am reminded of things like:


So a Miller Genuine Draft long neck holds 50kV seemingly without a problem.
 Remember that beer bottles are very high tech and the process of making
them is very highly controlled so quality is very high.  Even though the
glass seems thin, it's the best glass available and it is molded to very
high standards.


	G3 #1043