[ARC5] Mica Capacitor

Richard Knoppow 1oldlens1 at ix.netcom.com
Tue Sep 20 18:14:20 EDT 2016


     I suspect the writer didn't understand what the circuit does. Note 
that it does not say the caps are bad, only that they were not properly 
tested.  Having had some experience in the production of established 
reliability resistors my guess is that such testing is extensive, 
establishing the behavior over a large temperature range and other 
factors.  We had to test for temperature cycling, extreme voltage and 
dissipation overload, mechanical strength and some other stuff which is 
now beyond my memory. Someone was not watching the store.
    Not Micamold, they have been gone for decades, but it would be 
interesting to know who and whether it was an American company.
    BTW, I have never seen any actual statistics on the failure rate of 
Micamold. They had a bad reputation but I wonder how bad they really 
were.  As I discovered from my AR-88 rebuild Solar made a similar cap, 
were they as bad?  The caps in the AR-88 were probably made in the 
mid-1940s. They had high DF and were somewhat leaky but that is to be 
expected after some seventy years. The set also had numerous oil filled 
paper caps. All had sprung leaks at the terminals. No oil left in any of 
them, all leaked out into the bottom cover, yet the caps still worked 
and were no worse than I would expect any paper cap to be after all that 
time.  I replaced all of these with polypropylene caps.
     Arden, I like your quote in your signature line.
On 9/20/2016 2:45 PM, Arden Allen wrote:
>> Talking about capacitors:
>
>> <http://gpsworld.com/gps-iii-satellite-delivery-slips-because-of-capacitor/>
>>
>
> I'm wondering if the article got it backwards:
>
> "The capacitor is part of a series of circuit cards that take higher
> voltage power from the satellite’s power system and reduce it to a
> voltage required for a particular subsystem."
>
> Arden Allen
> KB6NAX
>

-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL


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