[Boatanchors] recapping with polyprop caps

[J Forster]

The link has the interesting statement:

     "In the case of some types of capacitors, such as ceramic disks,
multi-layer ceramics, or silver micas, there is no "outside foil", because the
capacitor is
     made of a single-layer, or stacked layers of dielectric material and
conductor.  The orientation of these capacitors makes no difference.  Also,
some
     higher-voltage film caps (typically the 1000VDC/450VAC and higher values,
such as the Orange Drop 716P high-voltage units) use a "series-wound"
     technique that has two separate sections, side by side, with a common
"floating" connection layer, usually at the bottom of the layer stack.  These
caps
     will have no inherent shielding either. "

The pic was of a 0.47 uF @ 1000 V unit.

This raises two interesting possibilities:

1. That the cap is, in fact, two caps in series, which is doubtful IMO. The
problems with this option are two-fold: W/o a pair of resistors, how can you
get the voltages to divide equally? Also, the connections between the two
sections would be pretty complicated to get the desired result. If the common
connection is at the bottom of the stack, BOTH ends are outside foil and there
is no shielding.

2.  Since the cap value is quite large, any stray capacitance to the outside
world would be very small by contrast.

I'd opt for the second alternative.

Best,
-John



jeremy-ca wrote:

> Explain that claim please.
>
> Carl
> KM1H
>
> ----- Original Message -----
> From: "Dave Harmon" <k6xyz at sbcglobal.net>
> To: "'Todd, KA1KAQ'" <ka1kaq at gmail.com>; "'jeremy-ca'" <km1h at jeremy.mv.com>
> Cc: <Boatanchors at mailman.qth.net>; "'J Forster'" <jfor at quik.com>
> Sent: Monday, February 25, 2008 12:20 PM
> Subject: RE: [Boatanchors] recapping with polyprop caps
>
> > Yep, that's right.....today's mfgd caps....at least the orange drops I
> > bought from Mouser
> > (new mfgd, not NOS) are not marked with this line.
> > However....the outside foil can be identified by this method.
> > http://aikenamps.com/OutsideFoil.htm
> >
> > Try it....it works. I used a marker to identify the outside foil....they
> > were not all on the right hand side either so this is worth doing.
> > Oh....in audio applications....it DOES matter.
> > I thought it wouldn't matter....but I actually tried it and it does.
> > And I'm not an audiophool.
> >
> > Regards
> >
> > Dave Harmon
> > K6XYZ[at]sbcglobal[dot]net
> > Sperry, Ok.
> >
> > -----Original Message-----
> > From: boatanchors-bounces at mailman.qth.net
> > [mailto:boatanchors-bounces at mailman.qth.net] On Behalf Of Todd, KA1KAQ
> > Sent: Monday, February 25, 2008 10:39 AM
> > To: jeremy-ca
> > Cc: Boatanchors at mailman.qth.net; J Forster
> > Subject: Re: [Boatanchors] recapping with polyprop caps
> >
> > On Mon, Feb 25, 2008 at 8:08 AM, jeremy-ca <km1h at jeremy.mv.com> wrote:
> >> The band end is the outside of the foil and is usually the side grounded
> >>  when used as a RF bypass. In audio or DC applications it doesnt matter.
> >>
> >>  Those capcitors are NOT electrolytic and are NOT polarized.
> >
> > Rule of thumb used to be: the right-hand side of the writing was foil
> > side when no band is indicated. No idea how this applies to today's
> > cap designs, I just got into the habit of sticking them in that way.
> >
> > ~ Todd, KA1KAQ
> > _______________________________________________
> >
> >
> _______________________________________________