[R-390] Caps

[Charles P. Steinmetz]

Dave wrote:

>Here's what I believe.
>
>1. There's no potential for distortion; the reactance is only 35 ohms.
>2. Ceramic leakage is innocuously low.

You are welcome to your belief -- but is it a belief based on 
testing?  Test for yourself.  There is much more to the complex 
impedance of a ceramic cap than its reactance, including a very 
nonlinear real part.  It doesn't take much distortion to create 
significant spurious responses and radiated QRM.  Don't forget that 
the distortion and leakage of ceramic caps are worse at elevated temperatures.

>Give us a few makes/models, and we'll call it a day.

The only caps I can recommend for C553 are film-and-foil ODs of the 
appropriate value (0.01 uF) and a voltage rating of 600 Vdc or 
above.  Series 225P, 715P, or PS will work (the Series is the first 3 
digits of the part number, or the second and third character in the 
case of Series PS):

225P10396X      600 Vdc
715P10396K      600 Vdc
716P10396J      600 Vdc
6PSS10          600 Vdc

I do not see any need to use caps rated at more than 600 Vdc.

Series 716P and 418P will also work, but they are special order 
items.  Some of the higher voltage rated 715P caps are also special 
order items.  Sometimes distributors have specials in stock because a 
large customer needed them, but they are generally rare.


Best regards,

Charles