Jim is right, because both ceramic and glass vacuum variables are
designed to be pumped and sealed just one time - when they are being
manufactured. Manufacturing involves many one-way steps such as melting,
welding and vacuum-brazing parts together; and it all has to be done in
custom made assembly jigs to maintain the tight mechanical tolerances.
Re-manufacturing is only cost effective for large, high-value
transmitting tubes. For a vacuum variable, the cost would greatly exceed
the replacement value.
However, as Jim points out, you can easily check the performance of a
vacuum capacitor with a hi-pot tester. The voltage breakdown of a
capacitor that has "come up to air" will be greatly reduced (although
some capacitors may still be usable in lower-voltage applications like
"C2" in a pi-network).
What specifically is the problem, Chris?
73 from Ian GM3SEK
>-----Original Message-----
>From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of Jim
>Thomson
>Sent: 01 April 2014 05:38
>To: amps@contesting.com
>Subject: [Amps] How, and at what stage in production, are vac variable
>
>Date: Mon, 31 Mar 2014 12:17:06 +0100
>From: Chris Wilson <chris@chriswilson.tv>
>To: amps@contesting.com
>Subject: [Amps] How, and at what stage in production, are vac variable
>caps evacuated?
>
>
>
>Anyone any insight as to how, and at what stage of their production,
>vacuum variable capacitors are evacuated? Do makers offer any service
>to check the depression in them and re-evacuate if required? Thanks.
>
>--
> Best Regards,
> Chris Wilson.
>
>## Dunno about when the air is pumped out and unit sealed. But if you
>require a vac cap that has ..gone up to air..or has a lousy break down
rating
>as seen on a high pot tester..and want it pumped out again,.. u will
be in
>for a rude
>awakening...aka sticker shock.
>
>## I tell folks to treat vac caps with kid gloves.... leave em in the
foam lined
>boxes etc.
>I have seen several that have lost their vac from misuse in the
workshop.
>If u have ever
>seen the price on a new vac cap..it will make u gag..and ditto with
sending it
>in to get re-pumped.
>Much cheaper just to get another surplus vac cap.
>
>Jim VE7RF
>
>_______________________________________________
>Amps mailing list
>Amps@contesting.com
>http://lists.contesting.com/mailman/listinfo/amps
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|