cap question

[Bill Layer]

Hey hey,

>does this mean I need a Polyester Cap?  I find them, but the tolerance is
>poor (+-20%)  the other Polys I find are the Metalized Polypropylene Film
>ones, but these are physically big (32mm), and it would be the most expensive
>part of the circuit (just about)...

The vintage of the circuit, as well as the values called out, should give
some good clues about just which 'poly' we're talking about. My guess is
that they are calling for polypropylene i.e. Sprague Orange Drop. A very
stable and cheap substitute would be the Xicon line of metallized
polypropylene parts. 

I'm not sure what to say about the MPPs you are describing; they don't
sound *at all* like MPPs to me. The size for one, and the cost. MPP is the
most compact, cost effective film type around. For example, Xicon
.10uF at 630V (!) are   85 cents each in lots of 10 or more. The .002 part is
probably around 25 cents in the same quantity. The part you are describing
sounds more like film and foil (i.e. Solen) than MPP...

The value, .002 is also in keeping with that line of parts. Whenever you
see these small values, think tube amplifier. Tube amps generally use
.001-.1uF parts for coupling etc. The small values are possible thanks to
the high-impedance nature of vacuum tubes. 

>beyond that, I can't find a .002uf CAP anywhere.  it jumps from 1 to 2.2uf.
>So what is the deal here?  

Where have you looked? Try places that supply tube parts, like Antique
Electronic or New Sensor Corp. If you need to, you can put two .001 in
parallel, or two .0047 in series for roughly .002uF.

>I guess I have two questions.  The one about the word "POLY" and one about
>.002uf CAPs.  yeah.  I think that's all.
>

Hope this helped. 


Bill Layer
Sales Technician
<b.layer at vikingelectronics.com>

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