Re: [Amps] Vacuum Variable Cap Rebuild

["Fuqua, William L." <wlfuqu00@uky.edu>]

Rebuilding a vacuum variable is not easy.
If you are checking out vacuum variables at a hamfest, pull on the shaft. If 
you can pull it out to any degree it is neat atmospheric pressure inside. If it 
fails that test it is broken. It does not take much gas inside to reduce its 
breakdown voltage. In fact, a little air inside is a lot worse than atmospheric 
pressure.


Bill wa4lav
________________________________
From: Amps <amps-bounces@contesting.com> on behalf of Larry Dighera 
<LDighera@att.net>
Sent: Monday, April 12, 2021 11:45 AM
To: Amps@contesting.com <Amps@contesting.com>
Subject: Re: [Amps] Vacuum Variable Cap Rebuild

CAUTION: External Sender


Hello Paul,

I suggest you ask August (AJ) Link who has been a Jennings distributor for
decades.  Here's a link: 
https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fsurcom.com%2F&amp;data=04%7C01%7Cwlfuqu00%40uky.edu%7C45a36f2133c3452fb7d708d8fdca024b%7C2b30530b69b64457b818481cb53d42ae%7C0%7C0%7C637538391353566477%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=0s5WSNL9YpTIofnqQPOph6Qj%2FQymG%2F0%2FyZNDxWjzD8k%3D&amp;reserved=0

    Surcom Associates, Inc
    5674 El Camino Real, Suite K
    Carlsbad, CA 92008 USA
    Phone (760) 438-4420

Best regards,
Larry
WB6BBB


On Sat, 10 Apr 2021 18:47:23 -0400, "Paul Christensen" <w9ac@arrl.net>
wrote:

>Anyone know if it's possible to rebuild a vacuum variable cap?  It would
>require a precision break of the seals, then evacuating the air with a new
>seal.
>
>A cap used on my 160m transmit "T" failed a few months ago.  While
>dismantling the antenna at the season's end, I brought the cap back home and
>purchased a Megger 230425 Hi-Pot test set.  After testing today, the cap
>repeatedly breaks down at 700V, although it's rated for 5KV.
>
>It would be a shame to discard; it's an expensive Jennings ceramic type with
>a range of 25-5000 pF.  Used, they're $1,500 ea. from MaxGain Systems.  I
>only need a range to about 1200 pF, so I can definitely get by with an
>alternate that's on the shelf.  That's not the issue.  I would like to save
>the cap if possible.  I'm not sure what conglomerate owns Jennings now but I
>doubt they would have a rebuild service when it's much more profitable to
>sell new caps.
>
>Paul, W9AC
>
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