[R-390] Bypass capacitors, R390 and SP-600 [WAS: saga continues...]

[rbethman]

  Andy,

The "inexpensive" Z5U are just fine!  I see absolutely NO reason to go 
to NPO types in EITHER the SP-600 OR the R-390(X) types of equipment!

Neither one had that type of component in it to begin with - at least 
from "MY" experience with a Northern Radio SP-600 and a couple of R-390As.

Bob - N0DGN

On 9/12/2010 3:53 PM, James A. (Andy) Moorer wrote:
>    Do you have any opinion on the composition of the ceramics? Should
> they be NPO, or can they be inexpensive Z5U?
>
> -A
>
> On 9/12/2010 1:56 AM, 2002tii wrote:
>> Roger wrote:
>>
>>> Some 300 Volt items will work well. Move up one decimal point .01 to .1 and
>>> such. You just get some more by pass. Cost is not the issue any more. Size
>>> is not the issue any more. Exact part number is not an issue any more. You
>>> need a good cap that filter out more than it lets in or does not filter out.
>> Going up in value with film bypass caps is probably not a good idea,
>> because it moves the self-resonant frequency of the caps down (and
>> unfortunately, modern wound film caps do not have appreciably lower
>> inductance than their forbears).  As we have discussed here before,
>> however, you can get MUCH BETTER bypassing performance by switching
>> from film caps to disk ceramics, owing to their much higher
>> self-resonant frequency.  In this case, going up in value is OK (but
>> definitely not necessary).  As I have said before, buy yourself a
>> large bag of NEW .02 or .05 uF/1000 V disk ceramics and use them for
>> all tube radio bypassing applications -- you will never be
>> sorry.  Keep all capacitor leads as short as possible -- as Roger
>> noted, feel free to use a different ground point to achieve
>> this.  And use spaghetti tubing as necessary to insulate the leads.
>>
>

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