[Boatanchors] recapping with polyprop caps

[jeremy-ca]

I still dont see anything that explains your statement that orientation make 
a difference.

>From my days in the Service Dept at National to the present Ive rebuilt 
hundreds of radios without the "benefit" of OD's. They all seem to work 
quite well.

Carl
KM1H




----- Original Message ----- 
From: "Dave Harmon" <k6xyz at sbcglobal.net>
To: "'J Forster'" <jfor at quik.com>; <Boatanchors at mailman.qth.net>
Sent: Monday, February 25, 2008 9:47 PM
Subject: RE: [Boatanchors] recapping with polyprop caps


See comments ****

Regards

Dave Harmon
K6XYZ[at]sbcglobal[dot]net
Sperry, Ok.

-----Original Message-----
From: J Forster [mailto:jfor at quik.com]
Sent: Monday, February 25, 2008 6:05 PM
To: jeremy-ca
Cc: Dave Harmon; 'Todd, KA1KAQ'; Boatanchors at mailman.qth.net
Subject: Re: [Boatanchors] recapping with polyprop caps

>>>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.<<<<

*****what they mean is that the above types of caps have 2 flat plates, one
plate is not inside the other one. The 715P has 2 plates as well but they
are not small squares of material, they are much longer strips that are
rolled into a tight 'rod' thereby making an 'inner' and 'outer' plate.
This is not me inventing this technique, this has been done for many, many
years and until fairly recently as stated by KA1KAQ, this type of cap has
always had an identifying band located to the right of the printing. The
purpose of this thread is how to identify recent mfg OD's without the
outside foil marking band....not whether these caps work as stated....which
they do.
Ever wonder why a lot of boatanchor receivers have been recapped with OD's?
If they are not....they likely should be.

>>>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 715P and 716P series OD look almost exactly alike however I believe
what they are saying THIS time is the 716P plates are wound in such a way as
that neither one is 'shielded'.
A kind of side-by-side bifilar winding.
The 716P caps are likely done this way for better insulation at higher
voltages.

>>>>>>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.
******you're right!


 >>>>If the common connection is at the bottom of the stack, BOTH ends are
outside foil and there is no shielding
*******both plates on 715P OD's are NOT outside.
.

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



> ----- 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.
> >
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