[R-390] killer and mica caps

[Renee K6FSB]

I am beginning to think that a fuse in series with the cap on the filter 
side might be the answer . just a thought .......
Renée, K6FSB

Francesco Ledda wrote:
> Given the small bandwidth of the IF, the frequency/gain variation created by the cap is negligible.
>
> Frank
> K5URG 
>
> Sent from my iPad
>
>   
>> On Oct 10, 2016, at 20:13, Larry H <dinlarh at att.net> wrote:
>>
>> Hi Chris,  I understand all of our desires to get this right, as i've had to replace bad filters, and it's no fun or cheap, and sometimes a crap shoot (is my replacement good).
>>
>> Here's some things to consider:
>>
>> 1. Any coupling capacitor introduces distortion into the signal path.  How much is acceptable is the question.
>>
>> 2. Adding another cap in series doubles the distortion, and doubles the required capacitance for each one.
>>
>> 3. If I use 2 caps in series, how often will I need to test both to maintain the desired level of safety?  Monthly? Weekly? Daily?
>>
>> 4. All capacitors fail eventually.  What is the desired and acceptable life for C553 and can I obtain that quality of cap?
>>
>> 5. Once a self healing event occurs in a metalized film cap, can it be determined that one did occur? No, and once they start, they reoccur at a quicker frequency.
>>
>> 6. The life expectancy of the best quality film and foil is much higher than a metalized film given they are rated at the same voltage and temperature.
>>
>> 7. Should I test the replacement cap under its rated voltage?  YES!  This is the safest way to be sure it will last.  If a new cap is bad, it will show up here.
>>
>> I personally believe that a 630 v SBE 715P (or related) orange drop is the best and 2 in series would not improve the safety factor very much at all and not enough to require weekly checking or endure the increased distortion.
>>
>> Regards, Larry
>> ______________________________________________________________
>> R-390 mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/r-390
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:R-390 at mailman.qth.net
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>>     
>
> ______________________________________________________________
> R-390 mailing list
> Home: http://mailman.qth.net/mailman/listinfo/r-390
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:R-390 at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
>