[Amps] Air variable pitting - repairable?

[Russ Williams]

Well, if it is the environment that is doing the cap in, and if you can dismantle the plates of the cap, you might try bonding a thin sheet of Kapton to the stator plates.  Of course, this assumes there is enough gap to accommodate .003" to .005" of Kapton.  Kapton is a fantastic insulator and can be found at reasonable cost if you look around. 

Just an idea...

Russ W6OHM


--- On Sat, 7/19/08, Jeff Maass <jmaass at k8nd.com> wrote:

> From: Jeff Maass <jmaass at k8nd.com>
> Subject: Re: [Amps] Air variable pitting - repairable?
> To: "'Carl'" <km1h at jeremy.mv.com>, amps at contesting.com
> Date: Saturday, July 19, 2008, 3:18 PM
> Carl (and others who have replied):
> 
> Thanks for the suggestions! 
> 
> The environment at PJ2T, perched on a cliff sitting a few
> feet back and 37 feet above the
> Caribbean Sea, is less than friendly to equipment. The air
> is carrying salt spray, the
> humidity can get high, and insects and small lizards crawl
> into placed we don't want them.
> 
> The inherent arcing problem Carl mentions below has
> probably been exacerbated by items 1
> and 2 above, and once it starts, it just keeps getting
> worse.
> 
> 73,  Jeff  K8ND
> 
> 
> > -----Original Message-----
> > From: Carl [mailto:km1h at jeremy.mv.com] 
> > Sent: Saturday, July 19, 2008 5:49 PM
> > To: jmaass at k8nd.com; amps at contesting.com
> > Subject: Re: [Amps] Air variable pitting - repairable?
> > 
> > No amount of filing and sanding will completely
> restore that 
> > plate to its original mirror finish. Microscopic rough
> edges 
> > will be the first place it arcs again.
> > 
> > Simply remove the plate and realign the remaining
> plates. One 
> > less isnt going to matter much anyway, even on 160
> much less 20.
> > 
> > TT has had arcing problems since day one due to the 
> > configuration of the Pi L; early caps even used Teflon
> sheets 
> > between plates.
> > 
> > Carl
> > KM1H
> > 
> > 
> > 
> > ----- Original Message -----
> > From: "Jeff Maass" <jmaass at k8nd.com>
> > To: <amps at contesting.com>
> > Sent: Saturday, July 19, 2008 4:59 PM
> > Subject: [Amps] Air variable pitting - repairable?
> > 
> > 
> > >
> > > We have a TenTec Titan III at PJ2T which is
> currently 
> > unusable because of 
> > > serious arcing
> > > on 20 meters. It is so bad that the amp will only
> run 300 watts.
> > >
> > > The problem is clearly in the loading capacitor,
> an air 
> > variable. There is 
> > > an area on one
> > > of the rotor plates that is burned and broiled so
> badly that it has 
> > > fattened up the rotor
> > > and it is nearly coming into contact with the
> stator at the 
> > spot where 20 
> > > tunes up best.
> > >
> > > Can this be fixed by sanding it down (and perhaps
> coating 
> > the plates with 
> > > something) or is
> > > this always going to be a "weak spot"
> on the capacitor that 
> > will start to 
> > > arc again?
> > >
> > > 73,  Jeff  K8ND
> > >
> > >
> > >
> > > _______________________________________________
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> > > Amps at contesting.com
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> > > 
> > 
> > 
> 
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